Overheating, FIXED EVERYTHING, Help

[brpansan]

My wonderful van has been overheating on me. I brought it to a mechanic. I thought it was the thermostat sticking becuase it would overheat one day and not the next. It was sporadic. He told me it was the water pump and radiator hose. Got those changed. Went to get van, van did fine. The next morning, broke down on the side of the interstate - overheated. I brought it back to the guy and said change the thermostat. He says I did not have one (dunno) so I told him to put one. I went to get the van and he said it should be good to go. Guess what......I was on the side of the interstate yesterday evening and this morning. I let it cool off, cranked it back up, and drove all the way to work. I didn't even go to the half mark once I cranked it again. I don't get it. What could it be? It overheats VERY quickly when it does overheat. Another thing it does sometimes is the needle will go almost to the red and then just drop back down to the C, while I am driving. I can actually watch it go up and down. Any ideas. Being a single mother of three, I am worried about a mechanic trying to just take my money like the last one did.

One more thing, it is not leaking fluids. My radiator is full, my resevoir is to the line it is supposed to be at. It has brand new fluids after changing the water pump, all of that is good. The oil is fine too.

[merc81]

Are you certain the engine is really overheating? My temp sender went out and behaved as you describe. Also, check the cooling fan as well. It won't generally be a problem if bad while driving at 40 or better, but the temp can be erratic when going slower if the fan isn't working.

[brpansan]

Originally Posted by merc81

Are you certain the engine is really overheating? My temp sender went out and behaved as you describe. Also, check the cooling fan as well. It won't generally be a problem if bad while driving at 40 or better, but the temp can be erratic when going slower if the fan isn't working.

I'm really not sure the van is really getting hot like it is telling me it is. I drove about 2 miles this morning, the temperature outside was about 60 degrees and it went all the way from C to the red. I pulled over and it cooled off quickly. I cranked it back up and it jumped to red again, I killed it again and it cooled off. About the third attempt, it stayed in the safe zone and I drove all the way to work.

A cop stopped and said that I didn't have fans blowing. I turned my air on and he said I then had one fan blowing. I am leaving my air on now, but it doesn't seem to work for me. Can the gage just be broken and giving me false readings? I'm one of those typical single moms and I am not real car savvy, I am at a total loss.

[merc81]

Ok, well don't leave the AC on just because it makes the fan(s) run. Its normal for the coolant fan to kick on with the AC because the heat load from the AC is expected to require extra air flow. Lots of cars just wire the relay dirctly to the AC control so it comes on like that.
Its not normal for only one fan to run however, both should be on. You will need to replace/repair the other fan at some point soon.

I think the overheat problem you describe is just your gauge sender acting up. Its not possible for the engine to cool down as fast as you are seeing. Have it replaced (cheap if you get someone to do that for you, easy screw in, screw out spark plug shaped unit) and I bet your problems are over.

[cdru]

Disagree. The sending unit is fairly basic thermister and isn't likely to fail that way. If it were to fail, it would read consistantly off and not fluctuate between hot and normal.

The symptoms you are describing sound like you have a bubble of air in your system. The air bubble gets trapped in the housing where the sensor is located and essentially becomes superheated. Starting and stopping, or revving the engine may force the bubble through and the engine cools down.

Next time it overheats, try to slowly open up one of the bleeder screws ever so slightly. There are two located on our vehicles. One is just after the thermostat housing before the upper radiator hose. The other is just to the right of the water pump on the front of the engine, on the bypass pipe. The one on the housing would be the primary one to open.

While the air bubble may be what is causing the engine to overheat, air bubbles don't form by themselves. Properly filled, your engine shouldn't have any opportunity to suck in air since coolant is drawn from the bottom of the radiator.

A failing head gasket would can force a bubble into the coolant. When my head gasket went earlier this spring, this is what was happening. I could drive for a few miles and the temperature would just shoot up. Bleed off the air/pressure and the temperature would go back down. I was able to limp home slowly that way.

Fill it up with coolant/water, then run it again. If/when it overheats, check your overflow bottle. Has the level raised? If so, you have something forcing air into the system pushing the coolant out.

[brpansan]

Originally Posted by cdru

Disagree. The sending unit is fairly basic thermister and isn't likely to fail that way. If it were to fail, it would read consistantly off and not fluctuate between hot and normal.

The symptoms you are describing sound like you have a bubble of air in your system. The air bubble gets trapped in the housing where the sensor is located and essentially becomes superheated. Starting and stopping, or revving the engine may force the bubble through and the engine cools down.

Next time it overheats, try to slowly open up one of the bleeder screws ever so slightly. There are two located on our vehicles. One is just after the thermostat housing before the upper radiator hose. The other is just to the right of the water pump on the front of the engine, on the bypass pipe. The one on the housing would be the primary one to open.

While the air bubble may be what is causing the engine to overheat, air bubbles don't form by themselves. Properly filled, your engine shouldn't have any opportunity to suck in air since coolant is drawn from the bottom of the radiator.

A failing head gasket would can force a bubble into the coolant. When my head gasket went earlier this spring, this is what was happening. I could drive for a few miles and the temperature would just shoot up. Bleed off the air/pressure and the temperature would go back down. I was able to limp home slowly that way.

Fill it up with coolant/water, then run it again. If/when it overheats, check your overflow bottle. Has the level raised? If so, you have something forcing air into the system pushing the coolant out.

I have no idea what you just said, but it sounded intelligent, LOL. I will print this out and keep it in my glove box so that the next time I break down, I can let whoever stops to help me read it and they can do what you suggested. Thanks for all the advice. I can use all the advice I can get when it comes to mechanics.

[merc81]

[quote=cdru]Disagree. The sending unit is fairly basic thermister and isn't likely to fail that way. If it were to fail, it would read consistantly off and not fluctuate between hot and normal.
<snip>

go back and read her first posting and mine too. She took it for service and the guy changed out the themostat, water pump, and a hose. No change in behaviour from any of that.

I HAVE experienced exactly what she is seeing and it WAS the temp sender. Its cheap and easy to change, way better than a water pump to pay for and is the logical next step before concluding its a head gasket or other problem. Also, the engine ECU would call for that fan to be running if the engine where really hot as the temp gauge claims but its not running unless the AC is switched on. Doesn't sound like a hot engine at all.

[GregA]

Could be several things, including (but not limited to) an air bubble (I have experienced that), bad sensor (or wiring to it), or the fan system. I have a description of how and when the fans should work HERE.

What you really need is a GOOD mechanic (or friend) that will take the time to actually troubleshoot the problem instead of just "taking a shot" at replacing parts that MAY fix the problem.

I suggest that you ask EVERYONE you know for recommendations about such a person. Once you find them, stick with them.

Take Care,

[brpansan]

Originally Posted by GregA

Could be several things, including (but not limited to) an air bubble (I have experienced that), bad sensor (or wiring to it), or the fan system. I have a description of how and when the fans should work HERE.

What you really need is a GOOD mechanic (or friend) that will take the time to actually troubleshoot the problem instead of just "taking a shot" at replacing parts that MAY fix the problem.

I suggest that you ask EVERYONE you know for recommendations about such a person. Once you find them, stick with them.

Take Care,

This is what I discovered yesterday. I broke down AGAIN, but finally made it off the interstate this time. I was able to get to a safe spot where I could get out of my van and pop the hood. I was never able to observe what it was doing while it was hot. Being a small woman, in Louisiana, I just stayed in my van with the doors locked and pepper spray in hand. The plastic tank was FULL, overflowing full, with bubbling water. The radiator was not. The water would not go from the plastic tank back into the radiator. I let it cool off, took the radiator cap off, and kept squeezing the rubber line that goes from plastic tank to radiator. It seemed to help and pumped the water back over to the radiator. I got on the road, same thing happened within minutes.

[cdru]

Still think it's a sensor problem Merc81?

With the tank foil of bubbling water, you have a head gasket that has gone south. The compression or combustion strokes are forcing air into the coolant system, which then displaces the coolant. This is something that needs to be looked at ASAP as it will destroy your engine via overheating.

If you have someone who knows their way around cars, replacing the head gaskets isn't difficult, just very time consuming due to everything that you need to remove to get to them. Do-it-yourself (free labor) will be less then $400 with everything that you should replace. Shop cost will be considerably more ($1500-2000+ maybe?) at the book time is around 20 hours IIRC when mine went south.

Head gaskets going south aren't uncommon on our vehicles. Often it's around cylinder 1 but not always.

[brpansan]

Originally Posted by cdru

Still think it's a sensor problem Merc81?

With the tank foil of bubbling water, you have a head gasket that has gone south. The compression or combustion strokes are forcing air into the coolant system, which then displaces the coolant. This is something that needs to be looked at ASAP as it will destroy your engine via overheating.

If you have someone who knows their way around cars, replacing the head gaskets isn't difficult, just very time consuming due to everything that you need to remove to get to them. Do-it-yourself (free labor) will be less then $400 with everything that you should replace. Shop cost will be considerably more ($1500-2000+ maybe?) at the book time is around 20 hours IIRC when mine went south.

Head gaskets going south aren't uncommon on our vehicles. Often it's around cylinder 1 but not always.

Merc81 e-mailed me with pretty much that same exact response. Definitely not the news I was wanting to hear. No way possible for me to even pay $100.00 on anything right now. Hurricane Katrina has me so far behind on everything. Thanks so much for everyone's help and suggestions. I'm gonna park the ole girl and make due somehow until income tax time rolls around.

[denyp]

Bridget

Don't feel bad - This has bit many of us venture owners. I have been a fair mechanic but this rig sent me south - I spent a lot of money before I got the problem solved. Mine started with sporatic overheating. I didn't know about the design defect in the intack manifold gasket. I put a lot of money in it till it overheated on me many miles from home and blew a head gasket. GM should be ashamed - biggest engineering blunder combined into one vehical I have ever seen in over 35 years driving.

Deny

[brpansan]

Originally Posted by denyp

Bridget

Don't feel bad - This has bit many of us venture owners. I have been a fair mechanic but this rig sent me south - I spent a lot of money before I got the problem solved. Mine started with sporatic overheating. I didn't know about the design defect in the intack manifold gasket. I put a lot of money in it till it overheated on me many miles from home and blew a head gasket. GM should be ashamed - biggest engineering blunder combined into one vehical I have ever seen in over 35 years driving.

Deny

I put the van in the shop AGAIN! The first time I spent over 300.00. Replaced the water pump, radiator hose and thermostat. Still overheating. Brought it to someone else. Paid 700.00 to rod out the radiator, replace thermostat again, they ran some sort of sealant through it for a minor leak in head gasket. Van did fine all weekend. It put me on the side of the interstate this morning, OVERHEATED AGAIN!. I let it cool off and cranked it back up. I drove for another hour in bumper to bumper traffic and it never went past the halfway mark. When it does overheat, all of the water gets stuck in the overflow plastic jug. It eventually goes back to the radiator, and then it does fine. Is that what the intake manifold gasket defect will do?

[cdru]

No. Intake manifold doesn't usually directly cause problems like this. Problems with the intake manifold are usually evident due to secondary damage. For instance, your bearings become damaged because your oil doesn't lubricate with antifreeze in it.

It sounds like you were screwed over twice by repair shops. If they were the same repair shop, I'd find someone else to take my car to. The $20 water pump and hose are a half hour job...hour if you include the fill and bleeding if you don't have a vacuum bleeder. The thermostat, while a possible culprit, can be easily tested while still installed. If the upper radiator suddenly becomes hot around 195 degrees when the car is idling, it's working correctly as the coolant just started to flow through. Likewise, the radiator is onyl $200 aftermarket. There isn't $500 in labor to replace that and the thermostat.

Because your overflow jug becomes filled, you have something pushing out the coolant. The coolant itself does not have that much thermal expansion. Air is getting into your coolant system somewhere. Continuing to drive and allowing it to overheat is only going to make the problem worse. Right now, presuming you have a reputable shop loook at it, your looking at a 1000-1500 bill for the heads and intake gaskets to be replaced. If you continue to let to go, you can add on another $500-1000 for replacement heads and other replacement parts due to cracking or warping.

[brpansan]

Originally Posted by cdru

No. Intake manifold doesn't usually directly cause problems like this. Problems with the intake manifold are usually evident due to secondary damage. For instance, your bearings become damaged because your oil doesn't lubricate with antifreeze in it.

It sounds like you were screwed over twice by repair shops. If they were the same repair shop, I'd find someone else to take my car to. The $20 water pump and hose are a half hour job...hour if you include the fill and bleeding if you don't have a vacuum bleeder. The thermostat, while a possible culprit, can be easily tested while still installed. If the upper radiator suddenly becomes hot around 195 degrees when the car is idling, it's working correctly as the coolant just started to flow through. Likewise, the radiator is onyl $200 aftermarket. There isn't $500 in labor to replace that and the thermostat.

Because your overflow jug becomes filled, you have something pushing out the coolant. The coolant itself does not have that much thermal expansion. Air is getting into your coolant system somewhere. Continuing to drive and allowing it to overheat is only going to make the problem worse. Right now, presuming you have a reputable shop loook at it, your looking at a 1000-1500 bill for the heads and intake gaskets to be replaced. If you continue to let to go, you can add on another $500-1000 for replacement heads and other replacement parts due to cracking or warping.

I've been screwed by two separate mechanics, one of them I actually know. I think it is time for me to just give up. I am going to drive the darn thing until it finally just blows up completely and hitch hike from there.

WARNING TO ALL OUT THERE, DO NOT BUY A CHEVY VENTURE, EVER!!!! DO NOT GO TO CAJUN AUTO IN WALKER LOUISIANA AND DO NOT GO TO BATON ROUGE RADIATOR IN BATON ROUGE LOUISIANA!!!