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C3 Engines

Engine overheating (1/18)
 6/13/17 7:34am
Dblancha79Gold Member
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Weatogue, CT - USA

Vette(s):
1979 C3 L82 350 cu in


Joined: 6/29/2015
Posts: 38

I have a 79' L82 350 engine and I can't keep it from over heating. I installed an aluminum radiator new hoses and thermostat. The electric fan temperature switch is new and fan rotates when connected to 12 volt battery.
After running the car for about 20 minutes if I stop and idle for 5-8 minutes the temp climes to 240F. If I turn the heater on it drops back to normal around 200F so that little extra heater core cooling seems to solve the issue.
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Any help would be appreciated on what to try next.


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"Made to be run hard"
Simsbury, Ct.
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Re: Engine overheating (2/18)
 6/13/17 8:13am
manchestersharkLifetime Member
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Equinunk, PA - USA

Vette(s):
1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.


Joined: 10/31/2007
Posts: 1990

How bout the thermostat being installed up side down. The little pointed dome has to face up/out. Is the fan blowing the correct way? Is it in front of the radiator or behind it?
Re: Engine overheating (3/18)
 6/13/17 2:00pm
gtr1999
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CHESHIRE, CT - USA

Vette(s):
1969 350 4 spd drop top 1972 350 auto coupe


Joined: 5/2/2016
Posts: 61

Can you confirm using a heat gun the fan comes on when it should? Did you use a DeWitt setup?

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Re: Engine overheating (4/18)
 6/13/17 2:28pm
Dblancha79Gold Member
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Weatogue, CT - USA

Vette(s):
1979 C3 L82 350 cu in


Joined: 6/29/2015
Posts: 38

I will double check thermostat direction.  My fan set up is  Radiator then electric fan then the engine fan. Both fans should be pulling air through the radiator.
Thanks


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"Made to be run hard"
Simsbury, Ct.
Re: Engine overheating (5/18)
 6/13/17 2:32pm
Dblancha79Gold Member
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Weatogue, CT - USA

Vette(s):
1979 C3 L82 350 cu in


Joined: 6/29/2015
Posts: 38

Yes I  can confirm with a heat gun but I am sure it is overheating. It will idle rough and stall if I push the gas too hard. almost vapor locks.  I don't know what a Dewitt system is but I will look it up.

Thanks


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"Made to be run hard"
Simsbury, Ct.
Re: Engine overheating (6/18)
 6/13/17 5:38pm
gtr1999
Limited Member
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CHESHIRE, CT - USA

Vette(s):
1969 350 4 spd drop top 1972 350 auto coupe


Joined: 5/2/2016
Posts: 61

DeWitts is a radiator mfg and one of the best out there.

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Re: Engine overheating (7/18)
 6/13/17 6:51pm
stingrayjim jrLifetime Member
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SHELBYVILLE, TN - USA

Vette(s):
1976 L48 auto

1978 L82 4speed

1994 LT1 6speed


Joined: 7/5/2002
Posts: 3942

If i picture this right, you have both fans on the engine side?..... so the clutch fan(the fan connected to the water pump) is right behind the electric fan...right???   first, i think i would place the electric in front of the radiator if you are going to use both fans, second, make sure the electric fan is blowing the correct way, in this case,  pulling air through and not blowing toward the front of the car......hook the fan up bypassing the temp switch and get a tissue or something of the like and verify the direction that the fan is blowing....
if you can put the fan in front, be sure to also put the fan shroud(if you have it) back on for the clutch fan,  as it does help
good place to start....


|UPDATED|6/13/2017 3:51:28 PM (AZT)|/UPDATED|


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StingrayJim
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Re: Engine overheating (8/18)
 6/13/17 7:11pm
manchestersharkLifetime Member
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Equinunk, PA - USA

Vette(s):
1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.


Joined: 10/31/2007
Posts: 1990

You could also by pass the temperature switch and wire it hot to a manual switch. That way you could turn it on and off at your leisure. It also assures you it's on and running.
Re: Engine overheating (9/18)
 6/13/17 11:05pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 565

Is the area between the A/C condenser and radiator clean? 

Are all of the seals around the radiator intact and in place? 

Is the air dam under the front end there? 

Might check the t-stat in boiling water to see if it opens all the way.  Saw a statistic once where about 20% of new ones are bad.

Is the spring in the lower radiator hose that keeps it from collapsing?

Assumptions I made are that the electric fan and engine-driven fan are operational.

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1973 L-82 4 spd

Re: Engine overheating (10/18)
 6/14/17 5:05pm
Toplander
Former Member

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Athens, IL - USA

Vette(s):
1975 coup 4speed leather interior. Silver with oxblood interior


Joined: 7/13/2016
Posts: 3

I have the same problem with my 75. I have a new Champion 3 core radiator with dual electric fans and fan shroud. I have removed the factory fan and clutch, changed thermostats from 195 to 180 and now back to 195 with a single 1/8" hole drilled in it. The fans come on at 180 degrees and are blowing the correct direction (pulling air through the radiator and blowing out towards the engine). When replacing the radiator i also replaced the core support, all the radiator seals and the air dam  underneath. My temp gauge reads 230 degrees which I have verified with a heat gun. So far I have tried everything i can come up with on forums except replacing the lower radiator hose, mine does not have a spring in it, but by watching it it does not collapse and both hoses are hard from internal pressure. Any Ideas?   

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