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Overheating question - help...please

7

78Chevy

Guest
This is the second that that I have been a proud owner of a 1969 corvette and I love it! I drove it yesterday - no problems. Today, right after I pulled into work, coolant started flowing out of the overfill drain line - alot - not just a couple drops. I have heard that overheating in these cars is the norm. I thought that I would ask the experts here. The 350 engine was rebuilt about five years ago and doesn't have any other leaks or problems that I can see. I am not sure what temp thermostat is being used. I asked the previous owner and he said that he thought it was rated at 190 degrees. Any thoughts or ideas?

Thanks to all,

Jim
 
T

thesurvivor

Guest
Replace ... or test....that thermostat. It's the easiest thing to check for now...
 
7

78Chevy

Guest
What temp thermostat is the norm for these cars?
 
T

thesurvivor

Guest
I think 180 degree thermostats are most common here. I use a 160 in my big block, but it will find its' own level, based on driving conditions and outside temps..
 
Joined
Jul 28, 2003
Messages
1,765
Location
Frankfurt/Germany
Corvette
1982 Collector Edition
I dont agree that car's overheat "as the norm".. even though i dont know a 69 C3..

What temp was it at when it overflowed ? Was the correct level of AC fluid used or was it overfilled (I've done that, dont laugh).. A correct system runs fine. In traffic, stop and go, standing around, they will run a bit warm, yes, but thats what the cooling fan is for.

:w
-Stefan
 
7

78Chevy

Guest
The car's temp was 200 to 210 when it overflowed. Traffic this morning was all stop and go and it was about 65 degrees outside.
 
T

thesurvivor

Guest
Well, that's not overheating.....may be too much antifreeze in the system....
 
Joined
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Messages
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Location
Frankfurt/Germany
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1982 Collector Edition
Go with what "thesurvivor" said: Check your thermostat.. Maybe it didnt open properly and a new one is all you need.. But i would also check the fluid level to make sure it didnt just dump out overfill.


:w
-Stefan
 
7

78Chevy

Guest
Thanks guys....I checked the fluid level in the overfill reservoir. It was a little low but not too bad. Maybe I am just a little too over-protective of my new baby.
 

Crimson Thunder

Well-known member
Joined
Dec 16, 2001
Messages
814
Location
Orange Park FL USA
Corvette
1970 Marboro Maroon Convertible
Make sure the fan clutch is working properly.If it keeps spinning(more than 2-3 revolutions) after you shut down the engine then it needs to be replaced.
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
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'67 Marina Blue Convertible
If the temperature gauge was indicating normal range and it "puked" after shutdown, it's probably a bad seal or weak spring in the radiator cap; with a good cap, a 50-50 mix of anti-freeze and water won't boil ("puke") until 265*F, and water alone (BAD idea) won't boil until 250*F. It's normal for temp to spike up somewhat after shutdown due to hot-soak (the engine is still putting heat into the coolant, but the water pump isn't circulating it through the radiator), but a good radiator cap will hold the pressure until the coolant temperature begins to go down.

If the temp gauge was showing abnormally high temp when you were driving, that opens up many other possibilities.

:beer
 

LVMYVT76

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Joined
Apr 21, 2006
Messages
664
Location
springfield, mo
Corvette
1976 medium blue
they used to be able to check caps with a pump-up pressure thingy. I used to test and sell a lot of caps that way when I used to work in a full service gas station. (that is giving away my age, since they are hard to find now adays) Make sure they are the correct pressure for the car. Try to find a/c brand if possible since that was on it to start with. I have heard some replacement brands don't work correctly, but don't have any written proof. The radiator might need flushed if it still over heats after everything else. I have put in an alum radiator, runs 30 degrees cooler, am going to put back in the 180 degree stat back in now. Dewitts make a great radiator, fits perfectly in the car, better than the original. Also if you have to replace the cor of the radiator MAKE SURE you measure the replacement, they are foreign and are about 1/4 wider which makes the radiator too wide to go back in. Believe me I have fought this before!!
 
7

78Chevy

Guest
Thanks guys for all the input. I understand that the caps are rated according to pressure. What rating would you suggest? If the cap doesn't fix the problem, I'll flush the system and check the thermostat and then on to the radiator.
 
B

bmotojoe

Guest
There are also seals that fit between the radiator support and the fan shroud. These tend to have dried out or have fallen off during a previous repair. Dr. Rebuild sells these kits and fit correctly. If your car is equipped with A/C the condenser may be full of dirt and not allowing good air flow. A good flush may help and also if the climate you live in does not get into the 30 degree zone during the winter you can use a 75 25 mixture of antifreeze instead of the normal 50 50 mixture. Also with a flushed system you can add a product called water wetter to the cooling system. I have heard of good results using this product. Myself, I like a radiator cap that has a safety relief handle.
 

Vettehead Mikey

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Joined
Aug 26, 2003
Messages
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Not that far from Ottawa
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1973 Coupe
Thanks guys....I checked the fluid level in the overfill reservoir. It was a little low but not too bad. Maybe I am just a little too over-protective of my new baby.

If you're filling it up each time, I can guarantee that it will puke shortly after engine shutdown. That's normal.

Let the reservoir seek it's own level and leave it alone.
 

black_81_vette

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Dec 1, 2002
Messages
295
Location
wisconsin
Corvette
black 81 corvette 4-speed
210 isnt way hot I would say the cap may be bad should be a 15 lb cap 17 will work too.Just make sure the like the others have said that the T-stat and fan clutch are in good working order.The fan clutch actually looses about 10% of its effective operation for every 10 thousand miles.
 
7

78Chevy

Guest
Got the car home and no problems. The car ran @ 205 degrees. I checked the cap and it looks to be in good condition. Also checked the clutch fan and I didn't knowtice any problems with it. Thanks to everyone for all your input - I hope that I can contribute as much to this forum as everyone here.

Jim
 

LVMYVT76

Well-known member
Joined
Apr 21, 2006
Messages
664
Location
springfield, mo
Corvette
1976 medium blue
Don't limit yourself to just what we have talked about. All parts of the cooling system need to be looked at. Water pump, fan and if you have the fan clutch on the car, collasped radiator hoses etc., All of these contribute to good cooling or not. Also a good temp sending unit and guage.
 

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