Normally as I cruise down the road my temp guage sits at about the quarter mark but yesterday the car overheated and got up into the red. I pulled over and let the car cool for 30 minutes and when I started it back up I discovered that when I cruise down the road it now sits about about the half mark. I was wondering if anyone has found that overheating the car will damage the thermostat or do I have a more sinister problem? I recently put in a 180' thermostat.

Thanks!

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84 Fiero with a 2.8 V6, Isuzu 5-speed, Performance Sound, Sprint Exhaust Manifols and a real pretty interior. :D

Been several pics posted of thermostats that were pushed off their seats and the 'handle was bent from being pushed against the bottom of the cap during overheating episodes. In that case, I would think the car would run cooler, not warmer. Are you sure the gage needle hasn't rotated on it's shaft?
I recently pulled the thermo from Jane's 84 to burp it after renewing the antifreeze and found the o ring gone from the tstat. Not sure if it came off when I pulled it out or what, but I had to get another. I'm guessing the missing oring is now resting in the inlet side of the radiator.

My theory is that the heat messed up the wax or something and it now opens late.

This of course doens't address why the car overheated in the first place... :P

quote Originally posted by Jeremiah: My theory is that the heat messed up the wax or something and it now opens late. This of course doens't address why the car overheated in the first place... :P

What wax?
The common cause if you were full of coolant for wver heating is either the pump or the thermostat. Replace it and see if the problem is persistant.

Isn't the thermostat contolled by the expansion of wax?

quote Originally posted by Indiana_resto_guy: What wax? The common cause if you were full of coolant for wver heating is either the pump or the thermostat. Replace it and see if the problem is persistant.

Depending on the exact situation... overheating can ruin a thermostat.

The capsule contains a calibrated wax pellet that works the plunger. The capsule can be damaged in a couple different way but the end result is you need a thermostat.

Colapsed thermostats are often a result of heater core/plumbing problems. see my cave for why.

The overheating can be the thermostat or several other things. Anything that restricts flow or allows air into the system is trouble.

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The only thing George Orwell got wrong was the year...

The Ogre's Fiero Cave (It's also at the top of every forum page...)

Here is a link that explains how it works. http://auto.howstuffworks.com/question248.htm It appears that wax IS involved.

I was wondering about this part of your cave:

quote The more ideal solution is to use an adjustable thermal switch on the radiator itself. The goal is to adjust this switch so that the fan is off most of the time but activates when you are stopped or in slow moving traffic. In these conditions little or no air moves thru the radiator and the temperature rises quickly.

Where do I get one of those switches to attach to the radiator? Currently my fan does not turn on due to overheating (though it does w/ the a/c) and my fan switch is stuck in the intake. This sounds like a perfect solution for me.

quote Originally posted by theogre: Depending on the exact situation... overheating can ruin a thermostat. The capsule contains a calibrated wax pellet that works the plunger. The capsule can be damaged in a couple different way but the end result is you need a thermostat. Colapsed thermostats are often a result of heater core/plumbing problems. see my cave for why. The overheating can be the thermostat or several other things. Anything that restricts flow or allows air into the system is trouble.

quote Originally posted by avengador1: Here is a link that explains how it works. http://auto.howstuffworks.com/question248.htm It appears that wax IS involved.

Nice link, I like it and you got a plus for it as well cause I DID in fact learn a new one, thank you!

The fan switch is in the head or the block. The temp sensor in the intake reads air temp and is used by the ECM.

Find the fan switch and ground the wire. It should be a green/white wire as I remember. If that turns on the fan then your switch may be bad.

You can get aftermarket adjustable swtiches any place that sells aftermarket radiator fans. These usually mount on the radiator. You can also get a lower temp switch from Rodney that turns on in the 120F range. That is probably the best range for most street driven cars.

I doubt that will solve your problem. If a car overheats when it is moving then something fairly major is wrong with the cooling system. The only time the fan switch should be a factor is when stopped or in slow traffic. If you are able to do more than 20-30 MPH the fan should not be needed. Many people that are using low temp switches or wiring the fan full time are just masking serious cooling system problems that will eventually get so bad even the fan won't help.

Then again how hot did it get? Allot of people seem to think 220 is over heating. It's not. 210-220 is perfectly normal for most cast iron engines. Even allot of Al ones. 230-240 is pushing some limits and many engines will start knocking. Boilover shouldn't happen until around 265 if your pressure cap and coolant are good.

No, this got up to ~250. As soon as it started to get into the red, I pulled over and let it cool for 30 minutes. After that, I got back on the highway and it stuck at 220... which I know isn't overheating, but when it normally sits at about 180-190 it causes some concern. The problem is intermittant but I do know the fan doesn't work.

I did get the fan switch from Rodney but I understood it was installed in the intake (next to the plenum).

quote Originally posted by theogre: The fan switch is in the head or the block. The temp sensor in the intake reads air temp and is used by the ECM. Find the fan switch and ground the wire. It should be a green/white wire as I remember. If that turns on the fan then your switch may be bad. You can get aftermarket adjustable swtiches any place that sells aftermarket radiator fans. These usually mount on the radiator. You can also get a lower temp switch from Rodney that turns on in the 120F range. That is probably the best range for most street driven cars. I doubt that will solve your problem. If a car overheats when it is moving then something fairly major is wrong with the cooling system. The only time the fan switch should be a factor is when stopped or in slow traffic. If you are able to do more than 20-30 MPH the fan should not be needed. Many people that are using low temp switches or wiring the fan full time are just masking serious cooling system problems that will eventually get so bad even the fan won't help. Then again how hot did it get? Allot of people seem to think 220 is over heating. It's not. 210-220 is perfectly normal for most cast iron engines. Even allot of Al ones. 230-240 is pushing some limits and many engines will start knocking. Boilover shouldn't happen until around 265 if your pressure cap and coolant are good.

[This message has been edited by Jeremiah (edited 10-23-2004).]

quote Originally posted by Jeremiah: No, this got up to ~250. As soon as it started to get into the red, I pulled over and let it cool for 30 minutes. After that, I got back on the highway and it stuck at 220... which I know isn't overheating, but when it normally sits at about 180-190 it causes some concern. The problem is intermittant but I do know the fan doesn't work. I did get the fan switch from Rodney but I understood it was installed in the intake (next to the plenum).

Sounds like it stuck open for you, it still needs replaced.
It is close to the thermostat housing.

[This message has been edited by Indiana_resto_guy (edited 10-23-2004).]

The water jacket flows into part of the V6 intake manifold... so that makes sense. I can never remember where the V6 sensors all go. There is a picture of them posted here someplace. You can go by the wire color at any rate. Check that wire and see if grounding it turn on the fan(s) as noted above. (It should also switch on the aux blower on 85-87 V6.)

Exactly how did you install the fan switch.... If you used teflon tape and some other sealants, the sensor may not have a good ground. That sensor must have good ground thru the threads to function. I recomend pipe dope rated for natural gas lines as it won't cause electrical problems. (Metal gas pipes have to maintain conductivity to disipate static electricity.)

I had thougt you ment it was installed in the air cleaner or ducts, which would not be right.

I'd definitely replace the thermostat. It's cheap insurance.

I think the sender for the gauge is in the head. If the fan switch is in the intake, a stuck thermostat may make the fan lag tuning on by blocking coolant flow into that area. IE the fan switch may not see the same amount of heat as the gauge.

The problem is, I didn't install the fan switch - the person who owned the engine before me did. Either the switch is seriously goobered up or it has been cross threaded and drilled all the way into the intake. A few guys have given me ideas on how to work around that, but I had nothing to do with the installation of that dumb thing and I need a drill to get it out.

Also... I drove about 120 miles today and had no problems at all... the problem is clearly intermittent. It's very frustrating. All I know is that the fan doesn't turn on at the correct temperature, but that doesn't explain the odd drifting to 220 and staying there until you turn the car off overnight, suddenly overheating without warning, overheating in 30 degree weather and not in 60 degree weather.... sounds a awful lot like a pump issue, don't you think?

quote Originally posted by theogre: The water jacket flows into part of the V6 intake manifold... so that makes sense. I can never remember where the V6 sensors all go. There is a picture of them posted here someplace. You can go by the wire color at any rate. Check that wire and see if grounding it turn on the fan(s) as noted above. (It should also switch on the aux blower on 85-87 V6.) Exactly how did you install the fan switch.... If you used teflon tape and some other sealants, the sensor may not have a good ground. That sensor must have good ground thru the threads to function. I recomend pipe dope rated for natural gas lines as it won't cause electrical problems. (Metal gas pipes have to maintain conductivity to disipate static electricity.) I had thougt you ment it was installed in the air cleaner or ducts, which would not be right. I'd definitely replace the thermostat. It's cheap insurance. I think the sender for the gauge is in the head. If the fan switch is in the intake, a stuck thermostat may make the fan lag tuning on by blocking coolant flow into that area. IE the fan switch may not see the same amount of heat as the gauge.

quote Originally posted by Jeremiah: Normally as I cruise down the road my temp guage sits at about the quarter mark but yesterday the car overheated and got up into the red. I pulled over and let the car cool for 30 minutes and when I started it back up I discovered that when I cruise down the road it now sits about about the half mark. I was wondering if anyone has found that overheating the car will damage the thermostat or do I have a more sinister problem? I recently put in a 180' thermostat. Thanks!

I don't know why your problem would be intermittent, but I have had overheating raise the opening point of a thermostat. It was consistent though.

GL

Jeremiah are you sure your eng is actually overheating? Here's why I ask. Not long ago, i noticed one of mine was running significantly hotter than normal, on a very short trip to the store. The rad fan should have been on, but wasn't. I went into the store, came back out, and started it up, and it was running cooler than normal on the way home. At 1st I attributed this to the thermostat opening while it sat and heat soaked, but it never did warm up on the way home. ran about 120 deg f. This erratic temp reading went on for several days, with it sometimes indicating extrememly cool-sometimes on the verge of being in the red, till i posted a query here and found the thread about the pegging temp gage needle, took a close look at the gage and realized the needle was loose on the gage shaft hub. The gage needle's calibration changed each time I started it, due to the deflection against the stop. I've exaggerated the appearance here, but if you look closely at yours you may find the needle may not be sitting squarely in the middle of the hub. It could account for your fan not comming on-it really isn't reaching high temp. I did fix the bulb test function and glued the needle back into the center of the hub and have had no more problems. the needle should sit straight in the center, not off to one side like the exaggerated pic on the right.

[This message has been edited by maryjane (edited 10-26-2004).]

Well, actually my temp guage doesn't peg - I fixed that. What it does do is not go all the way down to 100 (occasionally) when I turn the car on. Tonight it was really close... much closer than usual.

Is it odd that when the engine is 'overheating' the car drives just like normal and I can rest my hand on the plenum and it be only slightly warm?

quote Originally posted by maryjane: Jeremiah are you sure your eng is actually overheating? Here's why I ask. Not long ago, i noticed one of mine was running significantly hotter than normal, on a very short trip to the store. The rad fan should have been on, but wasn't. I went into the store, came back out, and started it up, and it was running cooler than normal on the way home. At 1st I attributed this to the thermostat opening while it sat and heat soaked, but it never did warm up on the way home. ran about 120 deg f. This erratic temp reading went on for several days, with it sometimes indicating extrememly cool-sometimes on the verge of being in the red, till i posted a query here and found the thread about the pegging temp gage needle, took a close look at the gage and realized the needle was loose on the gage shaft hub. The gage needle's calibration changed each time I started it, due to the deflection against the stop. I've exaggerated the appearance here, but if you look closely at yours you may find the needle may not be sitting squarely in the middle of the hub. It could account for your fan not comming on-it really isn't reaching high temp. I did fix the bulb test function and glued the needle back into the center of the hub and have had no more problems. the needle should sit straight in the center, not off to one side like the exaggerated pic on the right.

Sounds odd to me -- real overheating puts the ECM into emergency limp home mode, making the car barely drivable.

Tap your ALDL and see what the ECM sensor is seeing -- that signal is not from the same sensor as the gauge sensor or the fan switcht ... it might give you a clearer understanding of what is going on.

GB

Interesting... so heat CAN damage a thermostat. That explains some of my cooling system wierdness lately. Some back story...

A couple weeks ago, my car overheated while I was sitting in traffic. The cooling fan relay went bad, due to moisture (i.e. 3 hurricanes worth of torrential rain). I didn't know the relay was bad until the car overheated... DOH! When it overheated, the pressure split the plastic tank on the driver's side of the radiator... and somehow caused the expansion tank to split at the seam. I fixed all those problems. I patched the radiator, replaced the relay, replaced the expansion tank, and "burped" the cooling system.

But after fixing all that, I noticed that my temp gauge would go back and forth between the 1/4 mark and the 3/4 mark like clockwork... about every 20-30 seconds. I double-checked everything I had fixed. The radiator fan worked. There were no leaks. And there was no air in the system. That leaves the thermostat.

Keep in mind that I had replaced the thermostat with a Stant 180F degree one only 2 years prior, when I replaced the water pump. So I didn't suspect it at first. But when all the impossible was removed, then whatever remains...

I gave the thermostat the "boiling water" test on the stove. It didn't open until the water reached a rolling boil. So that was the problem. The thermostat was opening late. I got a new Stant 180F thermostat and everything's fine now.

At least now I know why the thermostat started acting funny.

What is the ALDL? I'm not sure what you mean. Yeah, pretty much the car drove like normal while overheating.

quote Originally posted by RGBaker: Sounds odd to me -- real overheating puts the ECM into emergency limp home mode, making the car barely drivable. Tap your ALDL and see what the ECM sensor is seeing -- that signal is not from the same sensor as the gauge sensor or the fan switcht ... it might give you a clearer understanding of what is going on. GB