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Hi all, new to the world of Corvettes I recently purchased an L-82 (1980) that runs nice and seems like a very solid car. I guess it was not being used much but it is having some overheating problems. It runs at 200-210 but goes up to 225-230 at traffic lights. After a few miles/minutes of highway (60-75MPH) and running at 200-220 when getting off and joining traffic it goes over 240, I have to do all sorts of things such as turning the heater on, stopping for a while and I had it boil the coolant once.
My mechanic replaced the radiator for an new aluminum piece with 12 12" fans, new water pump and hoses and new thermostat with a suplementary gauge. The Air dam seems to be placed correctly, and the levels of fluids seem normal and it still does the same thing... I dont think I have a blown gasket as the oil seems ok, no smoke or water. This is all WITHOUT using the AC, I tried using the AC once but it will go up to 240 even running on the highway and I live in Florida so I will need my AC! What am I missing? Any pointers will be much appreciated. Thanks!
From: At my Bar drinking and wrenching in Lafayette Colorado
The single most common problem with overheating as you describe is improperly set timing with defective or incorrectly hooked up vacuum advance. The first thing you need to do is to set your timing up correctly for 36 total and verify that the initial falls in the mid-teen range. Make sure centrifugal advance is operating correctly, and then verify that your vacuum advance is operational and that it is hooked up to manifold vacuum. This should provide about 28-30 degrees of timing advance at idle and low rpm. This has a HUGE effect on engine operating temp. Make sure this is set up correctly before chasing your tail on other peripheral issues. Nothing can compensate for badly set timing, and it will cause all kinds of problems, including low-rpm overheating. E-mail me for my timing and vacuum advance papers if you need specific instruction and specs to set this up right.
Lars V8FastCars@msn.com
Seems like a fan issue with new correct radiator.
what is the fan radiator mrf..
fanin right direction?
pics of both and seals?
did it have original fan and shrouding? Did you keep it?
spring in lower radiator hose?
they come with 195f thermostat…not your issue but would use a 180f
enough amperage available?
You can still have a blown head gasket without oil in water or obvious steam out the exhaust.
I would get a kit to find out whether it is or not blown. If it's pushing water out of the overflow then a blown head gasket is more likely.
There are of course, other causes. But it can eliminate or confirm the head gasket integrity.
From: At my Bar drinking and wrenching in Lafayette Colorado
The single most common problem with overheating as you describe is improperly set timing with defective or incorrectly hooked up vacuum advance. The first thing you need to do is to set your timing up correctly for 36 total and verify that the initial falls in the mid-teen range. Make sure centrifugal advance is operating correctly, and then verify that your vacuum advance is operational and that it is hooked up to manifold vacuum. This should provide about 28-30 degrees of timing advance at idle and low rpm. This has a HUGE effect on engine operating temp. Make sure this is set up correctly before chasing your tail on other peripheral issues. Nothing can compensate for badly set timing, and it will cause all kinds of problems, including low-rpm overheating. E-mail me for my timing and vacuum advance papers if you need specific instruction and specs to set this up right.
Lars V8FastCars@msn.com
The procedure that Lars is referring to will require a vacuum tool called Mity Vac. Those can be found on EBay for around $23. The kit comes with some hose adaptors, brake bleeding accessories, etc.
With the distributor cap off, hook up the vacuum pump to the distributor vacuum canister. Slowly apply vacuum noting how many inches of vac on the gauge is required to just barely start the advance arm moving. Write that number down. Continue with more vac until maxed. Write that number down.
If your dizzy canister requires 15" to actually move or advance and your engine is only providing 12" of vac, that could be a problem.
Just to start off, GM's cooling specs for the '80 Corvette are that the stat is to begin opening at 195°F and fully open at 227°F.
I wasn't concerned with your story until you mentioned boiling over; you definitely have an issue - regardless of what the gauge indicates. As Interpon requested, post a few pics of the engine from both sides without the air cleaner on. Your first step is as Lars commented - check your timing and advance. My suggestions are to also make sure the A/C condenser fins are open with no debris between the condenser and the radiator and to make sure the foam seals around and on top of the radiator are in place so air does not pass around/over rather than through.
You clearly haven't tried it all, because your still overheating.
I think I have tried it all. Over several years mind you.
I am no longer overheating.
This could be a very long response.
But I am not in the mood to type that much.
I live in Queensland Australia. Florida is a cool place compared to here. And I mean temperature wise.
Top things that make a difference.
Spring in lower rad hose.
Biggest 4 core aluminium radiator you can shoehorn in there! I mean it! Standard replacement is a waste of money.
REALLY good electric fans. The kind that blow a hurricane! Lose those cheap 12in. fans. C5 fans. Lincoln Mark VIII fan. Something that does something.
Heavy duty cooling option front spoiler extension.
Often referred to as a 79 part but is actually for 77-79.
The correct ignition timing as Lars mentioned above.
Incorrect timing will make heat that no cooling system can remove.
EVERY seal around, below and above that radiator. I even made up some new ones to fill gaps the factory missed. Absolutely no air should be able to go over, under or around that radiator! This is extremely important!
Those are the big things.
On my car I also run a high flow water pump and a high flow thermostat. My C5 fans never run going down the road at speed. But I have done all the above and more.
These cars love to run to hot. You have to have everything right!
Check your timing, as @lars mentioned. Do you have an IR thermometer to take an independent reading?
Make sure there is a spring in your lower radiator hose (you'll feel it when you squeeze it, it keeps it from collapsing). On the highway, you do not need a fan at all.
Is all of the foam insulation around the radiator? Stock dual-snorkel CAI still in place? Please post some photos!
Interesting comment about the stock aircleaner/ snorkel setup. An awful lot of us deleted the ugly factory air cleaner assembly. While it may be true that the slightly colder air may give the engine 1 or 2 more HP. It's relative restriction may also offset this.
none the less. In no way in all my testing/experiments in my own hot engine issues did the air intake make any difference in any way. Thus, this failed attempt wasn't mentioned, as other failed attempts also were not mentioned. Only things that made a difference were the things I did mention.
You clearly haven't tried it all, because your still overheating.
I think I have tried it all. Over several years mind you.
I am no longer overheating.
This could be a very long response.
But I am not in the mood to type that much.
I live in Queensland Australia. Florida is a cool place compared to here. And I mean temperature wise.
Top things that make a difference.
Spring in lower rad hose.
Biggest 4 core aluminium radiator you can shoehorn in there! I mean it! Standard replacement is a waste of money.
REALLY good electric fans. The kind that blow a hurricane! Lose those cheap 12in. fans. C5 fans. Lincoln Mark VIII fan. Something that does something.
Heavy duty cooling option front spoiler extension.
Often referred to as a 79 part but is actually for 77-79.
The correct ignition timing as Lars mentioned above.
Incorrect timing will make heat that no cooling system can remove. EVERY seal around, below and above that radiator. I even made up some new ones to fill gaps the factory missed. Absolutely no air should be able to go over, under or around that radiator! This is extremely important!
Those are the big things.
On my car I also run a high flow water pump and a high flow thermostat. My C5 fans never run going down the road at speed. But I have done all the above and more.
These cars love to run to hot. You have to have everything right!
I agree completely, and for at least the 1977 it can be confusing as what seal kit to order. I know the answer but what seals to order for the following,,, with A/C, without A/C but with HD cooling, or L48 with A/C but not HD cooling, the width of item B is different for each LH & RH
This photo below is the layout of a 1977 L48 with A/C, and with HD clutch fan but without HD cooling...
Interesting comment about the stock aircleaner/ snorkel setup. An awful lot of us deleted the ugly factory air cleaner assembly. While it may be true that the slightly colder air may give the engine 1 or 2 more HP. It's relative restriction may also offset this.
none the less. In no way in all my testing/experiments in my own hot engine issues did the air intake make any difference in any way. Thus, this failed attempt wasn't mentioned, as other failed attempts also were not mentioned. Only things that made a difference were the things I did mention.
The cold air itself wasn't the point. I was after two things:
1. Pictures! It is remarkable how much time is wasted on this Forum when a picture or two will immediately show the problem.
2. Without the stock CAI intake in place, there is a 2" x 12" gap over the radiator that cannot be filled with stock foam bits (like the ones posted above). The OP seems to have problems at idle AND at speed. So there may be multiple issues, but every bit helps.
My money is still on timing, with possible secondary issues that may include a head gasket, bad rad cap, and missing lower radiator hose spring.
Bonus picture! OP, is this part intact and in place? If not, a lot of air will bypass your radiator. My otherwise mostly stock car came with a replacement piece in this location.
Just for reference, in the picture I don't have all of the foam seals around the rad in my car, I'm missing the entire foam seal along the top, and I don't have any cooling problems at all. I have my ignition set up like Lars has described, run a 195* thermostat and run headers that allow a lot of heat into the engine compartment.... I also run the stock fan setup....engine is around 500HP. What I'm saying is the foam seals are important, but not the be all-end-all.
I suspect it's your fan setup that is causing problems. Do you have a shroud that allows air to be pulled from the entire radiator or is it just pulling air from in front of the fans...this is critical to getting proper cooling...having the fans mounted to a shroud so the whole radiator can contribute to engine cooling will always work better than fans just mounted to the rad.
A few pics would be helpful to us so we can see what you have.
But I see that no one has mentioned the fan shroud. It is critical on a C3. The mechanical fan viscous clutch can die and cause it to basically not work.
But it seems you already have 2 12" elec fans.
But do you have a good fan shroud for these that covers the entire radiator?
Lack of a fan shroud, or only a partial, will cause the fans to only pull air from directly in front of them, effectively giving you a much smaller radiator. The stagnant airflow in a C3 does not push air thru the rad very well by itself without any sort of fan. So the rest of the radiator is wasted.
Make sure your lower lip vertical spoiler is in place, or make a taller/deeper one, like the factory did on some of the later L82s.
What fans specifically do you have? many of them dont work worth a damn... thats said I agree you should double check your timing. Some pictures would go a LONG way here to help us help you.
We are glad you have decided to join us here on the Corvette Forum! This is the place to get answers for Corvette Issues.
As you can see the system works when you have questions. Personally I would start with the advice from LARS and work your way through the rest. Having "older" and sometimes original hoses on some of these Corvettes can actually be detrimental to the performance. People are so anxious to keep everything "original" that they forget to do simple maintenance like replacing vacuum hoses as they crack and dry out. The older coolant hoses can collapse under load when the engine is warmer and this is why they put a spring inside the Radiator return hose on the bottom of the radiator. When I first bought my C3 I went and replaced every inch of vacuum line as well as all hoses and fluids. Take a look and see if your C3 has a chart showing the vacuum hose layout and verify they are all there in the right place.
The one thing I will add to your list is to be absolutely sure that you are running a proper mixture of anti freeze with the distilled water in the coolant mixture. I have actually seen cars that were running too hot because they had 100% anti-freeze and no distilled water. 100% anti-freeze will make a liquid cooled engine overheat quickly. Most parts of our country can work with 50/50 water and anti-freeze, I too live in the South (Virginia) and don't need to worry about super cold temperatures so I use 70% water 30% anti-freeze and it keeps my high compression 427 running cool enough. Add a bottle of Redline Water Wetter to give the coolant an extra boost at removing the heat.
Be sure that the damper on the crankshaft has not spun, this will drive you crazy so I like to verify it is the right place. Simply rotate the engine until the timing marks line up and then verify the position of the Distributor as to where it is pointing. Most Chevy V8's will point at about 5:30 when the #1 cylinder is at TDC.
You should be able to get your 1980 C3 able to handle the heat of Orlando and then some. You will even be able to use your air conditioner during the summer months... My poor little 427 convertible didn't come with any A/C and I have to suffer through the heat.
I would agree with previous comment, timing might be off. If car is just standing still it shouldn't heat up that much maybe 200 to 210 at a stand still. Good suggestions given: I would check that your harmonic balancer also that it is not way out of whack possibly it has slipped. Check your fan clutch, a faulty water temp sending unit or gauge.
Overheating, tried it all
