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Okay so I’m not sure what is going on but I have a 4 speed 1980 vette that I just bought. I have zero issues when I drive around town but when I get up to speed and am in fourth gear for 15-20 min the temp gauge starts to rise. I pull over and let it cool off before it gets into the red but why only at high rates of speed?
I would think that is when it would be cooler. Any thoughts before I just start replacing parts?!?!? Thanks in advance for you input
I recently replied to another post where someone had overheating problems. I once had a similar problem where the car would only overheat at high speeds. Turned out the lower radiator hose was collapsing.
To check for this, rev the car and watch the hose to see if it collapses. You can also squeeze the hose to see if it is soft. Some no longer have the spring.
There should be a lower two piece rubber spoiler below the bumper. This forces air up to the radiator. Check to see if it is there. Sometimes they get damaged and are removed.
If you are going to drain it replace the hoses. Cheap insurance and if you are going to drain it a perfect time to do so. Are you sure your thermostat is working properly? again, perfect time to change it and both are easy to swap out.
I am not sure the thermostat is working properly. Thank you for the info . I will replace the hoses and thermostat at the same time i am flushing the system.
This is a great place for information. I have learned so much and I thank you all!
Shine a good light into radiator to see the fins and any crap limiting cooling.
how did you know overheating?
does turning heater on full fix?
pis od engine cooling?
Last edited by interpon; Oct 18, 2019 at 11:14 AM.
I was also thinkinig water pump, but that is a bit more involved than just a couple of hoses and/or thermostat. If the fluid is gone, personally I would think about doing a water pump also... except! I have not done one on my 76 Corvette so I might be talking out my backside, lol. It *is* pretty tight in there! That might fall into "if it ain't broke, don't fix it".
Nice car the Pace-car wheels look great.
Post up a picture of the radiator seals!
1. Clean radiator and Condensor core with high pressure water from the REAR. BLAST IT!
2. Check condition of the fan clutch....should RESIST you spinning it. If it is wobbly it's shot!
3. I can't remember if the 80 or the 81 was the first year of the electric AUX fan...check that and the thermoswitch in the head.
4. Pop out the thermostat and replace it with a 180°.
5. Check hoses for collapse/kinks or other.
6. Check A/F for density.....water is a much poorer coolant than 50/50 A/F (60/40)
Funny story...My friend shows up in my driveway with a C-4...."Hey Hal it's overheating!" I dive under the front and look at the front face of the condensor core...THERE'S a HAY BALE under the nose!
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I'm thinking a clogged radiator from the brownish coolant which is rust from the block passing into the rad. You may not see it because it has settled in the bottom of the rad clogging tubes. A flush will only remove loose particles. But it may correct your problem. What temperature are you calling overheating?
Since you're changing the thermostat anyway, you should fill the system through the thermostat location in the intake manifold, with the rad cap off. This will get the air out, which can be a serious problem.
Have you pressurized the cooling system to check for leaks? also remove the radiator cap and watch the flow through the radiator. I would not want to see any bubbling if so it could be a head gasket.
If it doesn't overheat at slow speeds, it's not a radiator problem. (Not saying the radiator might not need 'help'.) Only overheating when at higher speeds....problem is a collapsing lower (suction) radiator hose. Factory put steel spring in to keep it from collapsing. Spring finally rusts away (brownish coolant?) and hard working pump sucks the hose down so no coolant gets through. Common problems.
White on red 80 is just about the perfect Vette, and the best color combination.
Lot's of good suggestions above, and you should be fine already. If you are going to get the car up on ramps and/or jackstands, you may want to consider pulling the block plugs and flushing the block as well. Otherwise, checking for the spring in the lower radiator hose will probably do it. Do you have any run-on (dieseling) when you shut the car down? That might indicate a timing issue as well.
Here's a picture of draining the block on my car. There was a bunch of rusty crud that came out before the clean-ish antifreeze.
@Bikespace - is that a crossmember on a 4 post lift? I am going to get a 4 poster sometime, looking for ideas for something right along the lines of your pic... wheels off but lifted.
Over heating 1980 vette
