81 Corvette running hot......
Thread Starter
7th Gear
Joined: May 2006
Posts: 7
Likes: 0
81 Corvette running hot......
I bought my second Corvette about a month ago. Its an '81 and it runs hot. It warms up quickly and gets up to about 220 degrees after about 15-20 minutes on the highway (at about 3000-3500 sustained RPM). Will start to drop slowly if I turn AC off. Is this normal for this model? Help please!!!!!!!!!!!!
Le Mans Master
Joined: Oct 2005
Posts: 9,429
Likes: 44
From: Macon, GA
Your problem could be a number of things. However, based on the fact that you said it runs hot on the highway, the first thing I would check would be distributor advance system. If your centrifugal (mechanical) advance and/or vacuum advance is not working properly, it will make your engine run hot while cruising at highway speed because it is not achieving the proper advance needed under those circumstances. Use a timing light to see if either one is not working correctly.
Good luck!
Good luck!
Team Owner
Joined: May 2001
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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
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St. Jude Donor '06-'10, '13
Things to check:
Fan clutch
Electric fan
Radiator -- clean inside and out.
Radiator seals.
Lower radiator hose - is it colapsing at higher RPMS.
Temp gage - is it reading correctly.
Carb - too lean ?
Timing - is is right ?
Fan clutch
Electric fan
Radiator -- clean inside and out.
Radiator seals.
Lower radiator hose - is it colapsing at higher RPMS.
Temp gage - is it reading correctly.
Carb - too lean ?
Timing - is is right ?
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
81 has ecm controlled dist/timing. If the car runs good and accelerates strong there is nothing wrong with the timing. Retarded timing will make it run hot but will also exhibit weak power. The electric fan is an aux fan and I didn't find it very awe inspiring as far as a cooling helper, it does its job best in traffic, slow driving.
Look at the Air Dam below and in front of the Rad. Most of these cars have been run onto parking curbs ans whatnot which will push the air dam out of shape. With it bent/pushed up it will not allow proper air flow thru the rad and give those exact symptoms.
I could be wrong, it happens ( a lot)
Look at the Air Dam below and in front of the Rad. Most of these cars have been run onto parking curbs ans whatnot which will push the air dam out of shape. With it bent/pushed up it will not allow proper air flow thru the rad and give those exact symptoms.
I could be wrong, it happens ( a lot)
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Safety Car
Joined: Mar 2005
Posts: 3,503
Likes: 2
From: Raleigh NC
A thermal fan clutch will freewheel at any engine speed over 2800 rpm. It will not re-engage no matter what the temperature climbs to.
Basically you are running with no radiator fan and a large airflow blockage when you cruise at 3000+ rpm.
Late model L82's had a spring loaded flap in the shroud to allow air to flow freely on the highway and not get blocked by the freewheeling fan blades.
You can solve this problem by:
1. Installing an overdrive transmission. Or...
2. Installing a high rpm rated fixed race fan (not a flex fan.) Or...
3. Installing an aluminum radiator. Or...
4. Installing an underdrive pulley set. Or...
5. Installing a late model L82 fan shroud.
I went with the aluminum radiator from Dewitts--problem solved.
I do have the fan shroud and aux electric fan from an '81 in my '77. And it did keep the coolant temperature between 210-220 as stated. I just didn't like to cruise at 220F--it made me nervous.
The high rpm rated fixed race fan works the best and is the cheapest fix ($40-45)--air flow like you wouldn't believe (suck a deer right through the radiator.) But it's noisy and has got to hurt mpg.
Basically you are running with no radiator fan and a large airflow blockage when you cruise at 3000+ rpm.
Late model L82's had a spring loaded flap in the shroud to allow air to flow freely on the highway and not get blocked by the freewheeling fan blades.
You can solve this problem by:
1. Installing an overdrive transmission. Or...
2. Installing a high rpm rated fixed race fan (not a flex fan.) Or...
3. Installing an aluminum radiator. Or...
4. Installing an underdrive pulley set. Or...
5. Installing a late model L82 fan shroud.
I went with the aluminum radiator from Dewitts--problem solved.
I do have the fan shroud and aux electric fan from an '81 in my '77. And it did keep the coolant temperature between 210-220 as stated. I just didn't like to cruise at 220F--it made me nervous.
The high rpm rated fixed race fan works the best and is the cheapest fix ($40-45)--air flow like you wouldn't believe (suck a deer right through the radiator.) But it's noisy and has got to hurt mpg.
Last edited by PhotoVette1; May 22, 2006 at 06:02 AM.
Pro
Joined: Mar 2005
Posts: 683
Likes: 4
The most common problem withe the C3s getting hot is the foam rubber seals that install between the radiator and support. If these fall out and leave a gap then the air goes around the radiator rather than through it. These are absolutely needed. Next is thermostat for your car. You will need a 180 degree and get the robertshaw brand if you can find them. Next make sure your hoses are not collapsing, this is what the spring inside helps to prevent. And even though the spring is inside this is still no guarantee that they are not collapsing. If they are old replace them. These are the basics. Hope you find your problem.
Good Luck
Steve
Good Luck
Steve
