Temp Gague Reading Low

My temp gague is reading low even after being on for a long period of time. It only gets up to the middle or operating temp if it sits and idles for about 10-15 minutes. Then when I start driving it gets real low again. The heat also cuts in and out as it pleases, most of the time not getting very hot. What could be the problem?

http://img.photobucket.com/albums/v163/RoB51988/0af00bc5.jpg

The Service Engine Soon light is glowing pretty brightly, have you checked for codes?

Have you checked the level of the engine coolant level or had the cooling system serviced recently?

-Rod

The engine light its on because of P0420, probably because antifreeze going through the cat converter ruined it before I did gaskets over. I keep checking my coolant level and its always full in the overflow tank. I havent had it serviced yet though. Should I take it some where and have it flushed?

If you take it to get it flushed, I'd suggest you have them change out the thermostat at the same time. If you plan to keep the car awhile and the hoses haven't been replaced, you should consider that at this time as well.

-Rod

What would be the best way to completely flush out the system myself? I know while I was replacing the gaskets I left the plug on the bottom of the radiator open for like 2 or 3 days and still when I took off the heads there was still a good amount of fluid in the block.

I've tried a few different ways to get most of the af out like blowing it out of the block and the heater core, the two places that trap af. But the best way I've found short of turning the car upside down and removing the heater core, is to take a very small diameter long length of clear tubing, about the size of fish tank air bubler line. Maybe thicker is better, 1/4" or 5/16", but not bigger, so that you can fish it down it to the bottom of the engine and the heater core. I'm pretty sure you want to enter the heater core from the side fed from the thermostat/back of the engine side, but I'm not 100% sure which opening will get you to the bottom of the core without disconnecting the hoses, at which rate, you may as well disconnect them right at the firewall connections. TTBOMK, the only reasonable access to the bottom of the engine is from the thermostat housing where the upper radiator hose connects, and through the heater hose and bypass hose connections next to the thermostat housing.

In regards to my preferred method of flushing, I don't have one that I know is far better than another, so I can only suggest perusing via the Taurus page search function this subject. I myself would be interested in knowing a proven method of flushing the cooling system. There has been discussion on the power wash at shops that seems to not favor it. I have no opinion on it yet. The best method to clean a severely plugged radiator it to pull it and have it cleaned by a radiator shop. They really can get it clean.

Could it be doing this because of a small leak or my overflow cap isnt staying on tight enough? It seems like I tighten it down but then when I go to take it off to check the a/f it comes off easily.

That could be, but it could very well be a stuck open thermostat or one that no longer opens and closes as it should. It is also possible your problem could be related to a faulty radiator cap or the pressure releasing cap found on the overflow tank which would be in place of a radiator cap. That is, there is no cap on the radiator. I'd go ahead and replace it, as it doesn't sound right loosening like that and see if that fixes things as it is the easiest first fix. Make sure that what the cap screws onto is not boogered up as that may be leaking and responsible for it loosening. Without a tight seal, the coolant won't return to the radiator when it cools. If you are getting air into the cooling system, this definitely could be the source. Make sure the radiator is completely full and put a little extra coolant in the overflow tank above the cold line. Then run it several times to see if that gets it. If not, then replace the thermostat. When doing that, you will need to be sure you work out all of the air introduced by the repair. If there is an actual rad cap, I like to directly top off the coolant there if it is low and only when cooled off as it gets the air out faster and the coolant in faster.

I thought the coolant temp in your pix was about what is on my Taurus and Windstar, both 95s with the 3.8 engine, but I don't know what year and engine is your, so I don't know if it is a fair comparison. Once my, and for that matter, most all vehicles get to normal operating temp, the temp doesn't and shouldn't fluctuate too much while driving. While not moving, the lack of air moving through the radiator from car movement greatly diminishes the cooling and will definitely raise the temp guage reading until the electric fan(s) kick on until the temp returns to the normal temp on the guage. I kind of doubt it, but if the fans are coming on too often, you can have excess cooling, but from what you have described, I don't think that is your problem. Let us know how it goes.

Its a 96 Taurus GL 3.0 . I only have an overflow tank. I just did the head gaskets over so I replaced the thermostat and overflow tank cap at the same time the gaskets were done. I've already gone back to AutoZone to get another replacement overflow tank cap because I thought the first one was faulty. The second cap I got did the same exact thing. I would tighten it down and then the next time I'de go to check on it, it would be loose and come right off easily. The only time the heat gets really hot like its supposed to is when the car has been running in park and the temp gague is a little passed the middle of the operating range. When I drive and the cold outside air gets into the engine area it goes right back down to around where it is in the above picture.

I live in Boston and I took it down to New York City yesterday. Its about a 3 hour ride and the whole time on the highway the temp gague stayed low like in the picture. But once I got into the city and traffic it seemed to get into the middle or higher of the operating temp area. The car ran fine the whole way. The heat wasnt as hot as it should be but it was decently warm. I have a Contour that once it runs for about 10 minutes the heat is unbarable on high with high fans. I had the Taurus on the hotest it would go on high fan but it wasnt bad, it did get hot in the car after a while and I did have to crack the window a few times.

I'm also wondering if come the hotter months if it will run to hot and over heat instead of over cooling? Anyone know?

A few new thoughts come to mind since your last two posts. I assume this heat problem developed right after your head gasket job, which make me VERY suspicious of a possible piece of old gasket is holding the thermostat open all the time. Gasket also could have gotten to the heater core, though I don't know that it would be so easy to keep flow through it. Another possibility, but less likely to give you the heat problem unless due to trapped air, is the little jiggler/check valve/hole on the thermostat is not at the top. Also, the flat side goes towards the engine, which typically has the opening temp stamped on it, and the pointed side towards the radiator. My manual says that the tstat turns and locks in, but I don't know if that is true for your year and engine.


In regard to the pressure cap on the overflow reservoir, some have an overtightening prevention feature like the gas and oil caps. If yours has this, when it clicks, it should be tight enough. With it loosening, I'm suspicious of your tank filler neck threads being not right, out of round, something.

Do you know if the radiator fan is running only when needed and not too much? It will come on and off based on the temperature sensed next to the thermostat by the engine coolant temp sensor, either screwed into the intake manifold or inline to the heater core. It typically has a two wire connector to it. The sensor with one wire is only for the temp guage in the dash. For example, the fan would only come on and off when parked, if it ever gets hot enough. With winter temps, it may never come on while moving, but maybe at long traffic lights and like, the fan may come on. Otherwise, it shouldn't be coming on that much if at all.

On this business of cooling in the hot weather, it will behave the same way irregardless of the temp. So it won't over heat, it will just continue to cool more than necessary when the engine is cold. However, it may be hard to tell there's a problem or difference at all, because once the engine reaches operating temperature, the thermostat will stay open pretty much all the time. And as before, the cooling fan will go on and off based on the measured engine temp. Assuming the tstat is open too much, the only thing I can think of that could cause it to overheat in the summer is if the fan thermostatic switch or the fan goes bad. I can't think of anything that hasn't manifested itself in the cold that would when it gets hot out.

If the pressure cap were not sealing and that were the only problem, I'd expect a problem with overheating.

What year is the Taurus? Tripletdaddy's question regarding the operation of the cooling fan is a good one. The fan (or fans, depending on the year) is switched by the PCM with determines need based on engine coolant temperature (ECT). The ECT is determined based on the resistance of the ECT sensor. If the ECT sensor is reading the coolant temp as hot all the time and directing the PCM to keep the fans on, the radiator is not obstructed, and the water pump flows well, you'll never get the engine up to normal operating temperature.

It would be interesting to connect a scan tool to the car with datastream mode and see what the PCM thinks the engine temp is. The PCM ECT reading is derived from a different sensor than the gauge typically.

-Rod

Good point on the overheating possibility with a leaking cap, Rod.

For those of us who do not have the luxury of owning a data streaming scanner, :), an ohms/volt meter could be a cheaper and more available possibilty to measure the resistance and voltage of the ECT at different temperatures. The ECT is also a very inexpensive and easy part to replace, just be sure to get a brass instead of a plastic bodied unit.

With the electrical connector off, the ECT resistance should be in the range of 60 k-ohms when cold, below 50 deg F, to 1 k-ohms at 250 deg F, which if your engine ever gets hot enough and the pressure holds, it can get close to that. The ECT will be at 2200 ohms or less when the PCM will turn on the low fan, about an engine temp of 210+ deg F. It will turn off at around 2500 ohms, about 205 deg F, all measured with the wires off. The high fan speed will come on at ~225 deg F, ~1650 ohms and off at ~220 deg F., ~1800 ohms. If you find your measurements are consitent. but are shifted one way or another as a group, that would probably mean your ECT is ok. You're looking for readings way out of whack or measurements that don't seem to track with the temperature change.

With the wires on, the voltage backprobed on the ECT connector will be around 0.485 volts to turn on the low speed fan. All of this must be done with a full, air pocket free system.

That just got a little to technical for my experience. Is there another way of explaining how to test all of this to see whats wrong?:confused:

A scan tool with the datastream mode. ;)

-Rod

Oh, you're real funny Rod. :rofl: :shakehead Don't you think by now if he had a friend with one, he'd have used it by now? You certainly don't expect him to drive all the way to you and find his way through all those corn rows and corn husks?:screwy::tongue:. Maybe you could lone him yours by mail? And when he's done with it, can I borrow.......ok, ok.:wink:

Yeh, Rob, maybe I got a little carried away with the technical stuff. If you can get a multimeter, then you could take just a couple instead of a myriad of readings just to verify the ECT is doing basically as it should. If you wish to do that and want just a few readings to shoot for, I'll paraphrase to just a few pieces of info. To start, you could just measure things with the engine cold and then totally warmed up. If those readings aren't close, then replace it.

Have you observed whether or not the fan comes on at all as you would expect? Does it come on and go off as the temp rises and falls on your temp gauge inside? Be sure your AC and defrost aren't on, as they will turn on the fan even if the engine isn't hot. If the fan seems to basically do this, the ECT may be ok. I don't recall if you said that it does come on and off.

I had said before that you could quickly rule out the ECT by replacing it, but it is more expensive than I thought. $20 at Autozone. I like doing testing first rather than guessing by replacing parts between cost and uncertainty that it even needs replacing. Unfortunately, that may be the best or only strategy sometimes.

OK so I finally got a nice day here in new england to get outside and do some work on the car. I finally fixed the problem. I bought a thermostat at AutoZone which apparently wasnt the right temp for the car. When you change thermostats its supposed to be a 195 degree thermostat. I had a 180 in there which isnt that much of a diffrence. So maybe it was faulty or stuck open. I also back flushed and flushed the whole system about 4 times and a nice amount of rust and other crap was stuck in the heater core.

So now I have heat and a normal operating temp. :smokin:

Congrats, and thank you for posting a follow-up!

-Rod

I have a 96 model and my gauge looks exactly like that at normal running temp, i think they just read that way

But now the needle is more up higher and never gets down to the C line after having the car run for more than 10-15 mins.