I have a overheating problem. Driving home the temp spiked to the Red then back to about normal then bounced around then full red and I pulled over. I did find it was a little low on water but it should not have done this. Do you think it is a thermostat problem or a water pump problem? Please help as I need it. Where the hell is the thermostat anyway?

 

I would not think it would be yout water pump--Sounds like you may have air in your cooling system that needs to be purged---there are instructions on how to do this online OR you may have a failing or clogged thermostat--It is located on the front of the engine block on the passenger side near the A/C
This is assuming you don't have a radiator full of debris like leaves or paper bags---

 

I agree. Do the obvious things first like checking the condensor for a ton of tiny rocks in there and debris in general. Next, turn on the havc and insure that both fans are in fact running otherwise you need to look at the ground pack at the right forward frame rail where those grounds go through..plus check the fuses. Have you done any work lately that involved opening the coolant tank? Hopefully no one opened it and topped off the coolant with the wrong coolant.

 

Check for debris first. Check your hoses to determine if they're still viable. Replacement reservoir cap is inexpensive. Top hose maybe collapsing? If you need to burp it, try this...

http://forums.corvetteforum.com/c5-t...nt-change.html

 

Forgot to ask you about your FANS-----When the eng is HOT say 225-230* or over ----BOTH fans should be on---
With the A/C on the pass side fan should be on always at ANY temp---

If your car has never been tuned your stock fan settings are as follows---- #1 on at 226 off at 219
#2 0n at 235 off at 227
You could have a bad fan relay---OR your fan temp sensor is bad or pigtail fouled or unplugged--
Start the car dead cold---In your garage watch as the coolant temp rises---open the hood and look and see if the Drivers side fan kicks on-- untuned it should at 226* --- If tuned somewhat earlier----Turn on A/C and se if the pass side kicks on-------Turn A/C off and see if the pass side fan kicks on at 235 * untuned--- or if tuned somwhat earlier

 

Thanks for all the information. I will check the radiator for debris and I would think that is part of the problem. I did see both fans on at 240 degrees not sure if the one is on with the hvac but I will check in a few minutes. I really think it is a combination of everything. I guess I have to tear the front end apart to even see the radiator? Oh well.

 

NO Just get it up on jackstands----and with a flashlight you can see the whole radiator front--

 

But if you find obvious debris like grass/leaves/bugs, you might have better access to the upper areas of the radiator/condenser by removing the plastic cover beneath the air bridge. Otherwise the upper area continues to be clogged and disrupts air flow.

 

My own hunch is also air in the system. If so, how did it get in and where did the coolant go?

Another thing to consider is the current driving condition when the temperature climbs. Cars have cooling fans to increase airflow through the heat exchanger when the car isn't moving. If the temp climbs only when you are stopped you may have a fan problem. If you run hot even at freeway speeds you probably don't.

I rebuilt my AC system a couple of years ago and was shocked to find the top of the condenser blocked with sand and gravel. It was a chore getting that stuff out with a pressure washer with it out of the car. I regularly inspect my condenser for debris and didn't notice it from a simple on car visual. My car had only 50K miles and never overheated despite the clogged condition(and it gets really hot in central Texas). Also consider, if the problem were caused by debris, the condition would worsen gradually over time, not abruptly.

I have a Mazda that gave me fits with cooling diagnosis until I sprang for a cooling system pressure tester. It tests the cap and the cooling system for it's ability to hold pressure. In the case of the Mazda, there was a small internal leak preventing the system from attaining operating pressure. The coolant boiled into the engine and escaped through the exhaust. Weird problem that only came to light once I could see that the system wasn't holding pressure.

Just random thoughts intended to help you determine whats wrong with your car.

 

I took the airbridge off and also the cover over the radiator and condenser. It is dirty but not horribly so. Not sure how to clean it as it will be a total bitch to get a hose in there. I also took the thermostat out and put it in hot water and it did open around 200 but only slightly so I am thinking it is really the problem? It is a one piece unit, I did not know that and tried to seperate it, that did not work out! I guess if you change the water pump the new pump has the thermostat seperate from the hose attachment. I am only able to get a stock replacement so that is what I am going with. I am moving to Phoenix in 3 months so I guess after I get down there I will find a 160 and change it.

 

Well I replaced the thermostat with a new one. I cleaned the radiator as best I could. Filled it with the proper coolant. I fired it up and followed the instructions to burp it. It is still running hot as hell no matter what I do. I think the water pump is toast. I am not getting any heat into the cabin even after setting it to 90 degrees.
So am I right is it the water pump??

 

Is the radiator getting hot? When you start it cold you should be able to feel the radiator hose suddenly get hot as the thermostat opens the radiator circuit.

 

A way to check and see if your water pump is working ---
Re-Install the old themostat---but cut out the old thermo itself out of the housing so that nothing is there-just an open hole---Now fire it up and see if it runs cool --If the pump is working it will run real cold for 10 minutes- or so----but then will heat up SLOWLY as running no thermo will let the water move too fast and it won't be cooled by the radiator---If it continues to run HOT rite after it warms up then the pump is not working or you have an obstruction somewhere in the cooling system---

 

Water pumps have a solid shaft from the outside to the blades inside. I've personally never heard of a shaft failure before. Are you sure the fans are running when its overheating on you?

 

Well I have tried about everything. I let it set all night checked the water level which was just about right. took it for a drive. It worked great for about 10 miles coming to temp just fine and staying there. I stopped and idled for about 2 minutes took off and it got hot, the fans came on but it would not cool down. I stopped for about 10 minutes fired it up it went to normal temp them started getting hot again. I made it home and let it set again. I opened the coolant tank and let it run for a minute, then put the cap back on and ran it again and it got hot again. I now have it up on ramps and have taken the top hose off of the tank and put the hose in it and opened the petcock on the bottom and rinsed it out. No debris or anything came out and it seemed to flow just fine. The only thing I can think of is the damed water pump! I guess I will order one up and replace it? I have tried everything else besides pulling the radiator out and blowing out the debris but it does not seem all that bad. Any advice would be great! I am totally stumped!

I am throwing a Hail Mary and buying a new radiator cap just for grins. I really don't want to change the water heater.

 

Are you getting bubbles or blasts of air or whatever out of the tank?

 

when I loosen the cap there is definitly air escaping and possibly bubbles. This only happens when its hot. I drained the radiator and ran water thru it to see how it flowed and it seemed pretty good. The bottom and top hoses seem to be getting filled with water as the do heat up, I do not see them collapsing under pressure.
I just fired it up after filling with water and air escaped but I know there is more air in there as I drained it. I have also been checking the exhaust for water and the smell of the coolant, nothing so far.

 

Burp the air then seal it for the night and let it cool off completely. If it sucks in what's in the tank, that's a good sign. If it doesn't, then it could be something far worse. Hope for the best.

 

Dude, take a look at your engine, C5's have 2 electric fans and NO mechanical fan off the water pump shaft.

FOLLOWING EDIT ADDED LATER:

As pointed out by later posters, I misunderstood his remarks. I usually think of the water pump VANES not blades. When he said blades, I was thinking FAN blades. My apologies.

BTW, I did have a 1964 Corvette water pump shear off at the fan bearings, it hit and punctured the radiator. Never heard of anyone else having this problem.

 

Check your oil dipstick, is the oil milky white? If so, you have probably blown a head gasket. Oil mixing with water is NOT GOOD, don't drive it if this is the case.