overheating-strange case

The coolant in my 1998 4-door Taurus overflows the overflow tank after the car has been turned off. Eventually, after a few weeks the coolant level gets so low that the car overheats (if I don't add extra coolant on a regular basis). I have taken it to the mechanic twice yet the problem still persists, even though they changed the overflow tank, thermostat, and a number of hoses. Anyone have any idea why this problem persists? I thought that maybe the radiator fans should run after the engine was turned off to cool the coolant down (as happens in some other cars), but my understanding is that the Taurus is designed so that the fans turn off with the ignition switch.

WELCOME TO THE FORUM! Nice to have you aboard. The senario you describe is not at all unusual.
The fans shut down with the engine. Is the radiator clear of excessive amount of bugs and debris so there's plenty of air flow thru the fins? Love bugs get horrendous and can stop up the radiator cooling fins. Is the coolant relatively clean and free of rust and crud? Do you have the correct amount of anti-freeze to water ratio, shouldn't exceed 50-50 mixture. If you don't live in Siberia USUALLY a 40% antifreeze 60% water will suffice. Also note anti-freeze enhances the cooling properties of water. Long shot here, but is the system clear of obstructions and is the inside of the radiator free from obstructions. Have you ever flushed the cooling system and reppaced the old anti-freeze with new? The thermostat could be sticking and if it has never been replaced do it and be sure to use ONLY the temprature Ford recommends for your engine model year. They're cheap and easy to replace on the Vulcan push rod engine and make sure to replace the gasket or O ring for the t'stat housing.

If the coolant level was low before you shut down then some of the coolant gets turned to steam.The reservior, (overflow tank), caps do wear out and should be replaced when a groove forms in the rubber. The system is designed to run with 16 lbs of pressure and if less then the water slowly dissipates. Also, you could have a blown head gasket which can cause air pockets in hot areas like the heads and/or block and when you shut down the bubbles fill with coolant and creates steam pushing the water out the reservior cap. Another clue is white smoke or steam coming from the tail pipe. First get a new cap and if you experience the same probelm go to the parts stores and ask for a blown head gasket test kit and check it out.

Fact: The number one cause of blown headgaskets is overheating so one way or the other get it fixed soon because the way it is every time you drive it increases potential for more damage. If it overheated in the past it only takes ONCE and you could very well have a blown gasket.

I believe there's a test kit where you take some of your coolant and put it in a container then add some of the test kit chemical and if the coolant turns a certain color that indicates exaust/combustion gases in the coolant. Let's hope not . . . Caps are cheap so do the new cap first and let us know what happens.

Suggest you take time to read this which better explains info I provided.
http://www.arrowheadradiator.com/preventing_cylinder_head_gasket_and_cooling_system _failures.htm

Thanks for your reply, Huney1. The link was appricated as well.

To answer your questions, the rad has been flushed twice, the anti-freeze changed twice, the anti-freeze is a 50/50 mix, the thermostat has been changed, the overflow tank and cap have been changed, and there is no white smoke.

As implied above, the cooling system works fine when the engine is operating. No overheating regardless of the load on the engine (hills, long or short trip, a/c running or not, etc.). The usual fixes don't seem to have worked, which is perhaps why the AAA mechanics I have been taking the car to have not been able to fix the problem.

"The usual fixes don't seem to have worked, which is perhaps why the AAA mechanics I have been taking the car to have not been able to fix the problem." Did they test for a blown head gasket and if not that should be the next test you can do yourself. Water pumps in Tauri are famous for the blades wearing way down and don't pump the right volume of coolant circulation causing strange problems and they change the pump and everything is OK. No way to check the blades but take the pump off so if you take it off might as well replace it. Try this: Drive it as normal then shut down then turn the key back on and watch the temp gauge and see if it goes in the red zone. If it goes red then how can that be possible with the engine shut down? Hot spots or bubbles.

Sounds like you've covered the basic diagnostics and I believe it's a hot spot or bubble described in the link. When you shut down something is causing the coolant to boil and if the system contains the proper amount of coolant no air bubbles or hot spots in the engine that shouldn't happen. A bubble can be caused by not being FULL of coolant or blown headgasket pumping hot combustion gases into the cooling system creating a bubble-hot spot. The water pump could have a bad seal but I should think it would be easy to detect water leaking from it. However, you shut down and coolant hits the hot spots and creates steam and what you are experiencing can happen. Park it overnight over concrete and see if there's a puddle under it in the morning. Anxious to hear from the pros Monday.

Thanks for the suggestions, Huney1. I tried driving the car as usual, turning the engine off, waiting a few seconds, turning the ignition on, and looking at the temp gage. For better or worse, when I turn on the ignition again, the temp gage goes back to its original position about midway on the gage. In other words, the gage does not move up into the red zone, even though the coolant rises in the overflow tank above the appropriate level.

I also attempted to purchase a test kit at both AutoZone and Checker. Neither one had the kit. Do you happen to know where I could purchase one?

Thanks again for your help in attempting to solve this problem.

I found this using good ole Google: "Purchase an engine block leak detection kit from your local NAPA autoparts store Part Number 700-1006 for under $50. This kit uses a fluid that changes color when it chemically reacts with coolant containing exhaust gas. Again, I wouldn't drive it until you do the test because you could easily compound the problem."

"Thanks again for your help in attempting to solve this problem." The pleasure is all ours Sir and we take great delight in helping good folks like you. I'm dyslexic and it takes me a half hour to do this because I have to go back and edit it ten times making corrections. Wierd because I think I type coolant and I actually typed tnlooac, but when I looked the second time it looked OK but upon re-reading it was all garbledy-gook.

Please understand, diagnosing problems without hands on advantage is sometimes as frustrating for us as it is for the person with the problem. We often wonder WHY the shop didn't check the obvious and in your case I do not understand why they didn't test for exhaust gas in the coolant.

I find this interesting. "I tried driving the car as usual, turning the engine off, waiting a few seconds, turning the ignition on, and looking at the temp gage. For better or worse, when I turn on the ignition again, the temp gage goes back to its original position about midway on the gage. In other words, the gage does not move up into the red zone, even though the coolant rises in the overflow tank above the appropriate level."

Hmmm . . . Veddy interestink . . . . Causes me wonder if the temp gague, or coolant temp sensor, is working correctly. Parts stores should sell a thermometer for sticking in reservoir coolant to see what the temp is and I believe a regular meat thermometer with a probe would work.

As a matter of interest, I found a post where the guy bought a new cap for another make auto and it did the same thing as yours and he CLOSELY inspected the rubber washer in the cap and it had a slight defect not holding pressure. Take a magnifying glass and look at your cap AND where the cap seats on the reservior. The two must be a perfect match because if not then you lose pressure in the system. He took the cap back for exchange and the problem went away. When you replaced the t'stat, was it the temp Ford recommends?
I'm shooting at shadows trying to cover all the bases here but extremely interested in what the coolant test kit reveals.

For our moderators: I believe it would be a good idea to put the NAPA part number in a sticky or someplace readily available like, EASY TEST FOR A BLOWN HEAD GASKET OR CRACKED BLOCK.

Hi Dhodge.

I'll be pleased to hear how you resolve this one. My wife's 195,000 mile 1997 Taurus has developed this problem, too. Seems like I added some antifreeze in the spring and was perplexed as to where it went.

She pointed out to me that it was boiling over after shutdown about a month ago, but it seems to have gotten worse. Generally, the engine will still run fine. I've always done all of my own mechanicing, so I haven't taken it to anyone or bought any new parts, but this one has me stumped. I did replace the radiator cap yesterday with high hopes--I drove it until warm with no leak, but She just phoned me and said it was still happening.

I havn't checked the codes, but it has a check-engine light from a bad fuel-tank pressure system purge valve--never seemed like it was worth a couple of hundred bucks to fix.

As for Huney thinking it's the head-gasket, that's perplexing to me--it isn't losing the antifreeze out of the head gasket--it's coming out the radiator expansion cap, right before my eyes. I can hear a boiling in the head on the pass side front. The oil is new and clear, no evidence of coolant (white emulsion).

As as for the temp sensor being wrong, I guess that's possible, because we know it's really hot when it's boiling, but I think it's a localized hotspot that's causing the flash-over. The temp sensor is over on the otherside of the engine, as is the thermostat.

If it is a localized problem with the head or the exhaust (do I smell a funny, hot smell?), it'll be real work to fix the engine.

As for all of those people that love to dog the Taurus and say how their car is better, I'll just say that our '97 Taurus has gone the 195,000 miles without any major maintenance, and for that matter, the only thing that I've ever replaces was the transmission position sensor. I've never seen a car that didn't break. Lots of older Taurus on the road, too.

I'll be following your thread. I don't have to fix her car right away because we have a backup. If anyone else recognizes these symptoms...

"As for Huney thinking it's the head-gasket, that's perplexing to me--it isn't losing the antifreeze out of the head gasket--it's coming out the radiator expansion cap, right before my eyes. I can hear a boiling in the head on the pass side front." It wouldn't surprise me if the gasket is blown in that area and if it is repeatedly subjected to overheating the head could crack. I found this with Gogle: "Whenever there is a breach in the head gasket (http://www.rxauto.com/head+gasket+questions.htm), cracked head and or block, a hot spot develops at the point of the breach. This hot spot can reach temperatures 3 to 4 times that of normal engine operating temperatures. When Thermagasket comes into contact with this superheated area, it instantly forms a perfect high-temperature seal!"
http://www.rxauto.com/ http://www.rxauto.com/application.htm First time I ever saw it advertised so don't know if it works or not.

"As for Huney thinking it's the head-gasket, that's perplexing to me . ." All we can do is diagnose from afar without having the vehicle here in our hands and having went the route with
Dhodge the only logical thing I can think of is the blown head gasket or cracked head.

"it isn't losing the antifreeze out of the head gasket . ." Correct. The pressure inside the combustion chamber far exceeds pressure inside the cooling system so the the combustion chamber gases escape THROUGH the blown head gasket INTO the cooling system and creates a hot spot bubble 3 to 4 times hotter than normal engine tempratures. Lets talk about that . . . Normal engine temp is about 190 to 200F degrees, so if the hot spot gets 3 times hotter that's about 600F degrees! WHOA! That's hotter n' a two dollar pistol! Where there's a hot spot bubble the coolant doesn't make contact with that spot thus creating a hot spot. (See previous link I gave with details about bubbles and resulting hot spots.) If the leak happens to be near an exaust valve that can produce super hot hot spots.

"it's coming out the radiator expansion cap, right before my eyes." Correct again. When you shut down it no longer pumps combustion gases into the cooling system so the coolant begins to reach the six hundred degree hot spot creating super heated steam pushing the coolant out the cap. Are you getting the picture now? I don't know any other way to explain it but believe, I ain't just flappin' my lips and the verifies the info I gave you.

"Purchase an engine block leak detection kit from your local NAPA autoparts store Part Number 700-1006 for under $50. This kit uses a fluid that changes color when it chemically reacts with coolant containing exhaust gas. Again, I wouldn't drive it until you do the test because you could easily compound the problem." Look, until somebody steps out and gets a test kit were shooting in the wind for distance, so get the kit. Spend the $50. bucks because if you keep driving it the repair bill could FAR exceed $50.

Only thing we didn't do is change the radiator hoses and water pump.

"If anyone else recognizes these symptoms..." YES, YES, YES! Opinions, thoughts and comments very much appreciated. Jump right in and get your feet wet and certainly would appreciate some professional help here. At least tell us we're not barking up the wrong tree.

Well, Hrench—glad to hear that I am not the only one with this problem. And Huney1, I can relate to being dyslexic. While I don’t have problems typing (apart from my natural slowness), I do have problems speaking. The sentences are clear in my mind, but when they come out of my mouth, a lot of the time the words and phrases are inverted so that things don’t make any sense at all.

Ok—time for an update. The NAPA part number (700-1006) doesn’t seem to work on the NAPA website when I tried it for some reason. However, with the wording you provided, Huney1, I was able to do some searching of my own and found that AutoZone (but apparently not Checker) does carry a “block tester”.

The part number is 27145 and here is the link:

http://www.autozone.com/initialAction,allResults/initialNtt,block+tester/storeId,2765/shopping/selectStore.htm (http://www.autozone.com/initialAction,allResults/initialNtt,block+tester/storeId,2765/shopping/selectStore.htm)

One also has to purchase some testing fluid (unfortunately, I don’t have a part number for the fluid). Altogether, the block tester and the fluid costs about $30. I agree with you Huney1, that posting this information would be likely be valuable for other readers on the forum. Also, the PepBoys Auto chain, while not selling the block tester itself, does perform the test for about $30.

I preformed the test today and got negative results. More specifically, the test fluid did not change color as would happen if combustion gases where escaping into the coolant. Thus, it seems as if the head gasket is not leaking.

I also carefully checked the coolant overflow cap (which is supposed to be rated to handle 16psi) for any imperfections on the rubber gasket. I also examined the male end of the tank for similar imperfections. In both cases, no obvious flaws were apparent. The cap is a rather flimsy plastic device, however, which causes me some degree of concern.

In terms of the temperature gage, and the coolant temperature sensor, my sense is that these devices are working properly. The needle on the temperature gage rises appropriately as the engine heats up, stays pegged in the middle of the gage when the engine is running, and has risen toward the top of the temperature range when the radiator has become low on coolant, and falls again when I employ emergency measures (such as turning off the A/C). Consequently, I would be surprised to find out that either the gage or the sensor was working incorrectly.

Finally, I believe that the mechanics replaced the thermostat with a Ford product of the same temperature setting. The hoses that were replaced were Ford parts and I believe the thermostat was too (although I don’t know this for a fact). In addition, when the engine is warmed up, the needle on the gage goes to the middle of the temperature range. This is the same spot that the needle rose to when the old thermostat was installed, which suggests that the heat setting is the same.

Also, I am unsure how a faulty water pump could be causing the coolant to flood out over the top of the overflow tank after the engine is turned off. If the blades on the water pump were worn down, that would cause lack of coolant circulation, which would cause overheating while driving, I would think. Is there some way the lack of circulation would cause coolant to raise up and flood the overflow tank after the engine has been turned off?

So where does this leave me in terms of options? Here is my current thinking. As is the case with anything that I have written, please let me know if I am off-based or what is the best approach to take.

I have wondered if I should go back to the mechanic and ask for a new overflow tank and cap, or least a pressure test of the current tank and cap to make sure that it does, in fact, hold 16psi.

I have also wondered if perhaps I did the block test incorrectly. The instructions call for draining coolant out of the radiator and placing the tester on the top of the radiator neck to sense the gases. Since the radiator is quite difficult to get at on these Tauruses (behind all that bolted-on cowling), I did the test on top of the overflow tank. Since the radiator and the overflow tank are connected, gases that make it to the radiator should, at least in theory, make it to the overflow tank. I also wondered about taking the car to PepBoys Auto and having them conduct a block test to get a second opinion.

Another option would be to go ahead and try that “Thermagasket Head & Block Treatment Kit” you linked to Huney1. Maybe there is a headgasket leak but it is so small that the block tester doesn’t pick it up. Spending $100 would be worth it if it solved the problem. This option leads me to another question. Based upon the RxAuto website, thermagasket is one of a number of such products. I was wondering if this one is any better or more reliable than any of the other products that are available?

Lot of questions and discussion there and I'll hit the high spots.
"I also wondered about taking the car to PepBoys Auto and having them conduct a block test to get a second opinion." Yes, I would because if the test was not done correctly the results aren't trust worthy and Pep Boys diagnoses would be well worth the $30.00 "If the blades on the water pump were worn down, that would cause lack of coolant circulation, which would cause overheating while driving," I thought the same thing and I know it's wierd, but we've had participants that heater wouldn't work and the car never ran hot driving so it was pumping ample coolant to cool the engine but not go through the heater core. They took the pump off and found the blades worn WAY down and upon replacing the pump the heater went back to work. Now, aint that wierd? We're not talking a whole LOT of miles on the vehciles either and I was very suprised. Run a search for water pump blades and see what you can come up with.

I admit I am grasping at straws and based upon ya'll having covered the basic trouble shooting bases all I can come up with is the head gasket/hot spot thing. Thanks for bringing us up to date with the good info regarding the head gasket testers.

Only other suggestion is take it to the Ford place and pay them $75. to diagnose the problem, that's what they charge here. To my way of thinking I'd try replacing the water pump before letting them tear into the engine taking the heads off because the water pump is a whole lot cheaper. FIRST - Find out for sure about the head gasket or cracked head.

Long day today and I'm a weary senior citizen, so nite-nite.

Huney, I really appreciate your long 'senior' hours spent typing. I'll try to read the words even if they are bckawrads.

My problem exaccerbated Friday after my wife called me. Appears when she was running errands, she was getting multiple boil-overs and pretty much ran out of coolant. She said the needle never got outta the white arc, but after I brought her a jug of water on the highway, it still wouldn't start.

It did, however, start later so I drove it the 30 miles home in the 'limping' mode, planning to not exceed 45. I had added about two gallons of water. At first it got really hot on the highway--so I ran with the heater on full and the sunroof and windows open. When the heater stopped heating, I stopped at a gas station and to see what was going on and the coolant bottle was spraying out the of the bottom and the top--two places. First time I've seen this, so I'm pretty convinced that the system has seen higher pressures, possibly from exhaust.

When I refilled and got on the highway, the guage went back to the middle and the car was running fine. Went 70 with traffic. I hear a new noise that I associate with the assessory drive belts, so maybe the waterpump is at risk.

My new radiator cap seems to seal more than the original, but since the tank is leaking now, I still have a real heat problem.

Also noticed on the highway that it ran cool but when I had to stop and sit at an exit, it began to creep up. Makes me think water pump--Possibly it's siphon-pumping on the highway because the temp difference between radiator and block are different enough, but stops pumping at a stoplight because they're both hot.

I talked to a kid at O'reilly and he spoke really highly of the Bar's leak brand of head gasket sealer, only to find that his store didn't carry it. Said it was about $20 and it saved him a head-gasket replacment once. Told me to go to his former larger O'reilly store. I'm game. Remember, I'm working with a 196,000 mile engine--replacing the head gaskets is probably not a cost effective move.

Anyway, I've ordered a new bottle, I'm planning on doing the head-gasket seal stuff (the cheap-one--I can't imagine putting $100 into a voodoo online that I really don't think'll work) and if that doesn't do it, a new water pump. That's the most I'll spend on this engine--I've called around and I can get a low-miles salvage Vulcan 3.0 for $500 and put it in myself. Probably do the tranny too.

If the wtaer pump has never been changed I bet the blades are no more than dull nubs eaten away by time and electrolosis. At this point it has overheated and cooled of a lot so when you say it exaccerbated, that doesn't surprise me.

Bar's leak brand of head gasket sealer - I used a lot of to seal radiatiors but not head gaskets. You put in the coolant but the gasket would leak into the coolant therefore pushing the stop leak away. I thought it was for sealing an outward leak from the cooling system, but anything is worth a try. My guesstimate to pull both heads and run them through the machine shop do a valve job and mill the heads & put it all back together, . . . two grand or better. :runaround:

"Ive called around and I can get a low-miles salvage Vulcan 3.0 for $500 and put it in myself. Probably do the tranny too." That's the way to go because you'd habve less miles on the engine and tranny as well. We love our 03 Vulcan SES loaded with 53K mi on it still going strong and only repair was putting a power steering pump on it, the old one was howling like a wolf. Made in some sweat shop in Thialand so not Ford's fault and way out of warranty anyway.

Ford sez replace the serpentine belt at 60K mi so do that to and have the brake system and power stering system flushed and you should have a good ride that will last a long time. Let me know how difficult it was to replace the engine.

ok--I am going to try and replace the water pump. I went to the AutoZone website and found that Taurus' are equipped with one of four possible engines:

6 Cylinders 3.0L EFI (found in 68% of 1998 Ford Taurus)
6 Cylinders 3.0L EFI DOHC (found in 30% of 1998 Ford Taurus)
6 Cylinders 3.0L Flex Fuel (found in 01% of 1998 Ford Taurus)
6 Cylinders 3.0L Flex Fuel OHV (found in 01% of 1998 Ford Taurus)

The AAA repair shop stated that it was a OHV engine, which is very rare. Given the problems I have had with them, I am inclined to doubt their assessment.

I phoned my local Ford dealer and they said that 1998 is so old that they don't keep any records for it.

Anyone know how I can use the VIN or other method to verify the type of engine I have?

I believe there is an engine type in the serial number in the form of an alpha character/letter. Sorry but I don't know what they are but I would think parts stores would be able to get it out of the serial number. Basically there's the 12 valve push rod engine known as the Vulcan and the 24 valve overhead cam Duratech. I don't know about the other two and unless you have the SHO engine, (which I doubt), it should be a Vulcan or Duratech. I looked and my 03 Vulcan serial number 1FAFP55U93AXXXXXX. X= Number.
Come to think of it, I don't know the exact year the Duratech came out nor absolutely sure what engines they put in 98's. Call a parts store and keep calling until you find one that can help you. Try a used car lot and ask them because I am certain the serial number contains the engine type.

I called ADVANCE Auto Parts and they said only one water pump in the book for 1998 model year $39.95 so doesn't matter which engine you have. Get the pump and if by chance it doesn't match take it back and have them ordder the right one. Been doing busines with Advance along time and never had a squawk wabout them whatsoever.

I agree that a leaking head gasket is most likely the source of your overflow problem.

Another way to check for a leaking head gasket is to remove the intake manifold ond look up inside. Normally there is a thin even soot deposit but on cylinders with a leaking gasket, you will see an accumulation of soot and soot "lumps" ... the worse the leak, the greater the soot deposit.

dhodge,

I replaced the waterpump last night (O'reilly's has a rebuilt for 28.99 if you're in the midwest), but that wasn't the problem at all. I don't recommend you do yours.

BTW, the waterpump I took off (193K miles) looked as good as the new one I put on, ref the impeller. I don't know how people have problems with the 'wearing' down--you could still see manufacturing marks in the steel.

Felt pretty stupid replacing a good waterpump. The serpentine belt noise I heard turned out to be a failing idler pully bearing. Good that I found it, but not any real help now. Only took about two-hours--really easy pump to get to.

As for the head gasket, I observed that the coolant is turning to 'foam' when the engine gets hotter, probably because exhaust in it. I was able to buy the 'bar's leak' head gasket sealer at O'reilly's for only ten bucks. Not much lost if it doesn't work, but the proceedure to put it in involves lots of fill-drain cycles and I've already done the flush. It's clear. Arimid fibers.
http://www.barsproducts.com/1100.htm

Tell you tomorrow if this helps.

Wasn't kidding about the worn impeller blades, we have experienced a good many here. I wondered how they could wear down that much and my theory is the coolant must have been way high in acid pH and electrolisis & acidity ate them away. I put a new serpentine belt on mine a few months back and while it was off I did a spin job on the idler pulley and it seemed smooth & OK. 'Preciate the heads up and if I hear anything wierd I'll take my stethascope and put on it. Those things are excellent tool for finding the source of noises.
http://buy1.snapon.com/catalog/item.asp?store=snapon-store&item_ID=69022&group_ID=1411

Here's my update--in the last few days, I've replaced the waterpump, the thermostat, the coolant pressure/fill bottle, the serpentine belt (it needed it) and I've put 'head gasket repair' from Bar's leak in the system. My new radiator cap (from China) broke into six pieces, so I have the original back on.

I just did a ten-mile test drive at 95degrees with the AC on and it seemed to be cooling okay. However, when I stopped, I could hear the cap hissing.
No coolant escaped, but I'm pretty sure I still have 'the problem'.

The head-gasket seal stuff (wasn't clear after all) took lots of work to put in what with the flushes, the run for 15 min, the cool for 1 hour, run for 20 min, cool, leave open to air for 12-24 hours. If it had a bad head gasket, I think I'd see more symptoms.

BTW, Gary, I appreciate your intake manifold check advice--I haven't had the manifold off yet, but I may soon enough.

I'm starting to think that it might be excessive heat from the 'bottom end' of the engine, like maybe I spun a bearing or something. How could I tell if this was the case? The car make plenty of noises when I listen for them, esp. a whine at 45mph that repeats at about 65 mph (natural frequency's) but still stays at those speeds when I shift to third and get the rev's higher. I've believed it was bearing or tran related, but maybe not...

I'll drive the car to work monday (60 mile roundtrip) to see if it really happens to me. Seems like such a pain of a problem--oil looks fine, car runs fine, only one stupid symptom, but such a risk.

I'll keep you all up to date.

Dhodge, have you gotten anywhere with this?

"However, when I stopped, I could hear the cap hissing." That indicates it is not holding pressure and unless you have the required 16 lbs on the cooling system it will not work properly. Did we ever get a conclusive blown head gasket test and did you test the coolant for evidence of exaust gas?

Water boils at 212F sea level and with 16 pounds of pressure it 'probably boils around 240F. So with no pressure you're boiling at 212F and that's where your water is going in the form of steam or liquid coolant pushed out of the reservior cap. If the head gasket is blown a bad reservior cap will only compound the problem. You said the Chinese cap broke so take it back for exchange or get a refund and get a good one and put it on and see if you still hear the hissing.

"I'll drive the car to work monday (60 mile roundtrip) to see if it really happens to me." Be sure and take a 5 gal can of clean water so at the first hint of overheating stop and let it cool off and you have water to fill it up again. Get a new cap tomorrow and try that.

"Replaced the coolant pressure/fill bottle," No need for that unless it was leaking. :rolleyes: Get a new cap tomorrow. (Beginning to sound like a broken record here.) :slap:

Without re-reading all your posts, I assume you've run the simple head gasket check ... you run the engine until it's good and hot then, with the engine still running, you look into the top of the coolant overflow reservoir. Any air bubbles rising through the coolant indicate a leaking head gasket.

I would think the engine would be making loud noises if you had a spun bearing ... LOL.

Gary, it appears my first reply fell on deaf ears, this is an excerpt from my FIRST reply: "The reservior, (overflow tank), caps do wear out and should be replaced when a groove forms in the rubber. First get a new cap and if you experience the same probelm go to the parts stores and ask for a blown head gasket test kit and check it out." Is there any other way I could have said better?

Key words there are 'FIRST' and 'blown head gasket test kit' and I still say those should be done before moving on. Nine days ago I suggested those two things be done FIRST and now we've done a lot of work and spent money that may not have been necessary. :nono: :shakehead :banghead: Capish? Why not at least take Gary's advice and look for bubbles in the reservoir tank neck?

"when I stopped, I could hear the cap hissing. No coolant escaped, but I'm pretty sure I still have 'the problem'." Yes, you do, and the hissing cap is a BIG RED FLAG saying, "Hey, I'm hissing and I shouldn't be hissing, I should be sealed up tight, SO THROW ME AWAY, GET A NEW CAP AND REPLACE ME." What if you get a new cap and the problem goes away?

Gary sez; I would think the engine would be making loud noises if you had a spun bearing ...
AMEN.

OK, . . one more time; New cap & do a test drive. If the problem persists check for exhaust gases in the coolant. See, if one of those is the problem and you don't fix it, no matter what you do you will never fix it. Capish? Do that and we'll go from there, otherwise, the way it is now, I have nothing else to contribute.

Well, the good news is that I've driven the car more than 150 miles with no sign of another boil over. I'm thinking the problem is licked.

Gosh, Huney1, sounds like you're not pleased with me. No deaf ears here; if you read my earlier posts, the very first thing I replaced (Aug 3) was the radiator/pressure bottle cap. The Ford cap is back in place, but behaving exactly like the Chinese one was before it's snap-fits failed and it popped apart. It vents a small amount of 'air' on immediate shutdown, but because the hot-fill line allows 2-3 inches of empty bottle, no coolant escapes. Then it's done. I do intend to trade the broken-one in for a replacment, but I'm not sure I even care to have another low-quality cap.

As for the head-gasket-test-kit, my O'reilly didn't carry one and on top of that, we watched Dhodge spend the $50 to get in inconclusive result. I'm trying to fix this on-the-cheap, so instead, I just spent ten bucks on some head-gasket-healer huck-em-puck. I'm thinking it's done the trick. Or something else did. I would've looked for bubbles in the return line, but Gary1234 didn't suggest this until after I had put in the leak-stop. I do recall seeing 'foam' coolant and telling you all. but that was during flush with the cap-open. With no pressure, it's hard to tell what is unusual.

Just for reference to other mechanics that may be dealing with this, I've replaced the radiator cap, the water pump, the pressure bottle (visibly leaking, stretched along the plastic on the bottom, probably occurred during the high-pressure phases that caused overflow (??)), the serpentine belt, a bad idler, I've flushed carefully and I've put barsleak 1100 head gasket goo in the system and finally, I replaced the thermostat just to be safe, I know they fail. Adds up to about $100 total and something like four hours.

The things I don't think helped the boil-over problem are the waterpump and the cap. I don't know for sure, but I think the barsleak or the thermostat did the trick. I had to fix the belt, the pully and the bottle just because they needed it.

I've heard from others that leak-stop will only fix things temporarily. Well, I'm going to find out. I really didn't want to replace the engine this month anyway. I intend to keep this car, so I know we will eventually...

Dhodge, I'll still be pleased to hear how you get out of this.

Sorry for my delay in responding. My roof sprung a leak last week and I just found out that I likely have termites in my house as well (my two year old daughter asked me—what are these ants doing in the house)! Why does everything go wrong at once! Anyway, here is my update on the coolant-overflowing-the-reservoir-tank situation.

I spoke to the tech at Ford and he suggested the three most likely causes were the cooling fans, water pump, and head gasket. The cooling fans work fine so that is not it. Since my head gasket test was negative, and the overflowing problem is somewhat intermittent (I would think that with a leaking head gasket, the overflowing problem would be more systematic—happening every time I drive the car), I decided to replace the water pump, which I just finished doing today.

The old water pump is slightly worn. But my sense is that it is not worn sufficiently so as to be causing the problem. I will give the car a few test runs this week and report back later in the week with the results.

Ford charges $50 to diagnosis the problem, so if the new water pump doesn’t fix the problem, I think that I will follow up on Huney1 suggestions and let them look at it.

OK, it's intermitten & sounds like it loses coolant until it gets low enough to run hot. I can't remember everything you did, but the reservior tanks have been known to crack underneath where you can't readily see a leak and I guess you could take a light color rag and stuff it under there and leave it all night and see if the rag has a spot on it from a leak. If you don't park it on hard surface then put a piece of cardboard under the engine and see if shows a leak drip.

Sorry to hear you are having such an evasive problem to solve Dhodge and hrench. To figure out the engine you have sounds like your dealer is about as dumb and useless as tits on a boar hog!? Give me a break, "too long ago to have records for the engine vin id," blah blah blah. They got it. They just gave you the run around. My Haynes manual for "antique" Tauruses from 86 to 95 states that the 8th digit is the engine code. And it has the key to the code to determine what engine it is. So any decent manual should contain this information. Without looking for myself on mine, possibly the emissions tag or the top of the engine/air intake manifold may say. Hope this helps.