check theHypertech 160* thermostat make sure it is functioning properly. You can also drill 2, 1/8" holes in it to help with flow.
383 LT1 Overheating
Thread Starter
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
383 LT1 Overheating
1993 LT1 383 Auto
I'm having the common overheating problem. But this one is baffeling me.
It happens when the car is at a prolonged idle with the A/C. Its about 89* and humid outside (florida). It went all the way to 338* in 1-2* increments over a 15 min. period (from 196*).
So far I've blown out the debris from in front of the radiator with no luck in solving the problem. I've also checked to make sure both fans are working. I have the ECM programmed to turn the second fan on at 185* and it does. However, this isn't really relevant since the LT1 fans both turn on anyhow at any temp when the A/C is on. The waterpump is less than 2 years old and probably only has 10,000 miles on it. The radiator was also rodded out (where the clean all the gunk out of the cross fins with a poker, acid dipped, otherwise cleaned and new side tanks installed - all at the same time the water pump was changed. Also, the car has the Hypertech 160* thermostat in it (which at these temps is irrelevant). The coolant is a 50%/50% mix.. WTF?
As stated earlier the motor is a 383, with hyperutectic pistions at a 10.8:1 compression ratio. Comp Cam camshaft with spec similar to a Hot Cam (see sig). It blows when things aren't going your way!!
any ideas?
I'm having the common overheating problem. But this one is baffeling me.
It happens when the car is at a prolonged idle with the A/C. Its about 89* and humid outside (florida). It went all the way to 338* in 1-2* increments over a 15 min. period (from 196*).
So far I've blown out the debris from in front of the radiator with no luck in solving the problem. I've also checked to make sure both fans are working. I have the ECM programmed to turn the second fan on at 185* and it does. However, this isn't really relevant since the LT1 fans both turn on anyhow at any temp when the A/C is on. The waterpump is less than 2 years old and probably only has 10,000 miles on it. The radiator was also rodded out (where the clean all the gunk out of the cross fins with a poker, acid dipped, otherwise cleaned and new side tanks installed - all at the same time the water pump was changed. Also, the car has the Hypertech 160* thermostat in it (which at these temps is irrelevant). The coolant is a 50%/50% mix.. WTF?
As stated earlier the motor is a 383, with hyperutectic pistions at a 10.8:1 compression ratio. Comp Cam camshaft with spec similar to a Hot Cam (see sig). It blows when things aren't going your way!!
any ideas?
Burning Brakes
Joined: Apr 2002
Posts: 1,126
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From: Cleveland OH
Originally Posted by 383_BluByU
It happens when the car is at a prolonged idle with the A/C. Its about 89* and humid outside (florida). It went all the way to 338* in 1-2* increments over a 15 min. period (from 196*).
At any rate, I had issues with my electric cooling fan motor. The fans would function as expected, but the reality was that the fans were not spinning up to the correct RPM and thus moving less air around. New fan motors cured this for me.
Ron
Team Owner
Joined: Sep 2001
Posts: 62,153
Likes: 1,731
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
I hope 338 was a typo, because that'll blow a head gasket in a heartbeat.
I would have to doublecheck the gauge reading first, considering the cooling modifications you already have, then burp the cooling system one more time.
If that doesnt fix it, I would have to consider going up to a bigger radiator. I cant think of anything else it could be.
I would have to doublecheck the gauge reading first, considering the cooling modifications you already have, then burp the cooling system one more time.
If that doesnt fix it, I would have to consider going up to a bigger radiator. I cant think of anything else it could be.
Melting Slicks
Joined: Mar 1999
Posts: 2,535
Likes: 2
From: Rochester NY
Also, make sure that your antifreeze is a 50:50 mix. I used to have a mods trans Am keep getting overheat after the mods. I try everything it did not help. Then I add more antifreeze without add water. Boom the over heat if gone.
Bruce
Bruce
Instructor
Joined: Nov 2002
Posts: 119
Likes: 0
From: NC
Originally Posted by Bluewasp
try running the car without the thermostat installed and put the thermostat in a pot of hot water and see if it opens.
Removing altogether will do more harm than good as the flow will be too fast and the cooling effect will suffer.
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Verdad Gallardo
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
I have a 94 with a new LT1 with less then 5000 miles on it that does the exact same thing but I turn the AC off it gets above 230. I dont have a problem unless it gets in the high 80's and I am sitting in traffic for a prolonged time but the problem sounds verry similar to mine. I have also removed the radiator and given it a good bath with no help. I havent spent a lot of time on the problem since I am building my stroker now and plan on getting a new alm radiator when I drop the new motor in but am courios about what the cause could be. The slow fan is post is an interesting idea, I wounder if there is a possible problem from the factory with these fans?
Thread Starter
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
sorry.. 338* was a typo.. I ment 238*. Cooling fan motors were replaced 3 years ago (less than 20k miles).I dont think its the thermostat because when driving the car with the A/C off it runs a steady 186* almost on the screws... and when driving with the A/C it runs a consistant 198-212*. its only when stopped for over 15min at a stand still..
here is the best part.. I looked in the factory service manual for diagnosing the problem.. it said something along the lines of:
if the problem is overheating with the A/c under prolonged idleing inform the customer to turn the A/C off when prolonged idleing conditions exist - not further diagnostics are nessesary...
gee.. thanks GM!
here is the best part.. I looked in the factory service manual for diagnosing the problem.. it said something along the lines of:
if the problem is overheating with the A/c under prolonged idleing inform the customer to turn the A/C off when prolonged idleing conditions exist - not further diagnostics are nessesary...
gee.. thanks GM!
Drifting
Joined: Jul 2001
Posts: 1,296
Likes: 0
From: Largo Florida
Are the fans running at high speed? I don't remember if the fans have low and high speed settings (via the PCM). Is low speed one fan or both fans turning at a lower rpm.
I think if you had another Vette next to you to compare with while idling that you could tell by the sound, etc that the fans are turning at the correct rpm
I think if you had another Vette next to you to compare with while idling that you could tell by the sound, etc that the fans are turning at the correct rpm
Le Mans Master
Joined: May 2000
Posts: 8,729
Likes: 1,508
From: Redmond WA
The old "no thermostat will cause it to run hotter" is an old wives tale. It's not a great idea, since it delays warmup and hence causes increased wear and emissions, but the thought that the water can't cool off because its going through too fast is bunk.
Burning Brakes
Joined: Jun 2003
Posts: 937
Likes: 0
From: Bedford Tx
Originally Posted by DAVE396LT1
The old "no thermostat will cause it to run hotter" is an old wives tale. It's not a great idea, since it delays warmup and hence causes increased wear and emissions, but the thought that the water can't cool off because its going through too fast is bunk.
ope this helps.
