Overheating issues.

[Tkrahn77]

Hi my name is Trevor,

I am new to this whole forums thing but I have a question. I am by no means a mechanic but I understand quite a bit on vehicles. I'm more of a parts swapper. Well I have a 1990 ZR1 and have been going through quite a bit of issues since buying her. I have figured out most of the issues. I am now having over heating issues. I swapped the thermostat bled the air out still over heating. I removed the thermostat housing and cleaned up everything. I am looking for this sensor and wanted to swap it out but can't find it anywhere. If someone could direct me in the right path would be greatly appreciated. I am working my way up to the water pump and am hoping to solve the issue before getting to that point.


17996

17997

17998

[1991 Corvette ZR-1]

Have you had a chance to check the air gap between the radiator underneath the shroud? How quickly does it overheat? In changing the thermostat, how did you refill the coolant? When refilling the coolant and it appears full in the surge tank it is possible to still have a decent amount of air still in the system. A trick that one of our forum veterans taught me was when the engine is cold and you start it, put your hand on the coolant tube outlets on the injector housings and the cam covers. If the cam covers are getting hot, but the coolant tubes are staying cold, air pocket issues. If the tubes get hot and the cam covers stay comfortable to the touch during that time, you are good to go.

Also, surge tank should have a visible return stream while the engine is running. While the engine is cold, take the surge tank cap off and start the car and observe if that is present. You can also check your fan operation by using a paper clip to jumper the diagnostic terminal when the Key in the on position but not cranking it. That is a start anyway, hope some of that is helpful info.

[Tkrahn77]

I used the over flow funnel ran the engine for about an hour watching the flow of the coolant it did burp quite a bit. The temperature didn't get to high until I took it on a drive. Then it took about five minutes into the drive then over heated again.

[dredgeguy]

Not sure how many miles you have on the car but our C4's are bottom feeders, everything gets sucked up into the radiator. I had so much very fine grit in mine it blocked out the air. During one of our Wazoo maintenance days we took out the stock radiator and after an hour of shaking and tapping on it, fine grit material kept coming out. We knew there was no saving it. A new DeWitts solved that problem.

[Tkrahn77]

I have 71500 miles. I just ran water into the radiator from to hose the water flowed out clean steady flow. I did have a little debris inside the thermostat hosing assembly. I cleaned it out last night. I have yet to reinstall it and check to see if that could cause it to over heat.

[Hobbes]

I'm in Houston also and was experiencing some uncomfortably high temps while driving a couple weeks ago. I ended up removing and deep cleaning the radiator (30 years of dust/dirt/fur...etc), brushing/blowing out dirt from the other coils in the stack, installed a 170 degree thermostat and updated chip with lower fan turn-on temps from Marc Haibeck. I took it on a brief test drive this afternoon and it appears to be making a positive impact.

I'll try to go for a longer drive later today or tomorrow and report back. My bet is that 90% of the improvement came with the deep cleaning of the radiator.

[Hobbes]

Ran around town for about 45 minutes. Outside temp about 102. Mostly driving through neighborhoods with a few ?spirited? runs. AC blowing full speed the entire time. Monitored the engine/coolant temp through the hvac readout and never crossed above 98c or 208f.

Hope this helps give a gauge for you on next steps.

[Young1]

Pull out the radiator. You will find it clogged with sand and debris. I rake the fins with a fine wire brush we use on the Yorkies. I put screen on my air inlet too. Make sure both fans are running too. I was surprised how bad it was on at 40k miles.

[Matt B]

I agree with Steve. Last year I had to replace the radiator of my 2008 Audi A6 and was SHOCKED about the amount of fine sand and dusty debris that came out of that thing.
The accumulation of road dirt is crazy and for sure heavily affects cooling performance.
You can't eliminate that by flushing the system as this happens externally.

[Corvette95]

If you remove the radiator and entire front airbox (not air filter cover- the upper and lower shroud), while not exactly a pleasant job (read tech info stickies for help) , you will find access to the thermostat and hose much easier- congrats BTW on getting it out like you did). You will also have access to the oil filter housing and can fix any likely oil leaks you have there (they pretty much all do). Your fan(s) can also run and be bad at the same time. They just don't turn fast enough to do any good. Compare each fan to each other and make sure they run as needed with a/c pressure switch.

[Tkrahn77]

If you remove the radiator and entire front airbox (not air filter cover- the upper and lower shroud), while not exactly a pleasant job (read tech info stickies for help) , you will find access to the thermostat and hose much easier- congrats BTW on getting it out like you did). You will also have access to the oil filter housing and can fix any likely oil leaks you have there (they pretty much all do). Your fan(s) can also run and be bad at the same time. They just don't turn fast enough to do any good. Compare each fan to each other and make sure they run as needed with a/c pressure switch.
Re: Overheating issues.
I removed the upper and lower shroud. I did the deep cleaning of the radiator put everything back. Refilled the coolant bled the air and is still over heating. This is very tiring.

[richarde]

It may be worth checking that the flow of the coolant has not been modified by a previous owner, for whatever reason. I say that as I do not recognise the 3 photos that you included in your first post. I have attached a diagram of the stock coolant flow.18040


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[DRM500RUBYZR-1]

Using a coolant pressure testing tool determine if the system is maintaining pressure.

In 26 years my car never went over 230 regardless of conditions.
It usually operates in the 190-210 range.

Two or three years ago while in slow procession of 400 Vettes to the Ocean City NJ boardwalk, I was alarmed to observe a steadily climbing gauge confirmed by the digital as well.
When it went beyond 240 even with air on and revs up I really got nervous.
Was able to shut down when we finally got parked and was just below the real danger zone.

Driving home at high speed, I was able to maintain reasonable temp.
Every slow down caused a spike.

The cause?

The most minor leak around the lower hose. Minor enough that no drips were observed beneath the car, but enough to prevent the system from pressurizing.

Replaced with a screw clamp.
Problem solved.

Do not over pressurize it as you do not want to stress the heater core.

Worth a try.
Good luck and let us know.
:cheers:
Marty

[Jagdpanzer]

I agree, your photos are not of a typical stock cooling system.


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[DRM500RUBYZR-1]

I agree, your photos are not of a typical stock cooling system.


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Looking at the pictures, I agree.
However I now see there is also evidence of a long term leak that could contribute to the problem.
:cheers:
Marty

[Karl]

Re: Overheating issues.
I removed the upper and lower shroud. I did the deep cleaning of the radiator put everything back. Refilled the coolant bled the air and is still over heating. This is very tiring.

Is your water pump going out?

How did you burp the cooling system? You need to get the fluid level above the black fill tank with a large full funnel or such and bring up the rpms.