LT Motor Running Hot
Thread Starter
Burning Brakes
Joined: Mar 2008
Posts: 1,073
Likes: 8
From: Houston TX
LT Motor Running Hot
My 96 LT4 has been running hot the last few times I have driven it in stop / go traffic or let it idle for a long time.
It has been consistently about 90 degrees everyday as of late. I just was letting my car idle to see how high the temps would climb earlier today. 90 degrees ambient temp, coolant was at 215 and oil temp was at 219! A/C was set at 5. Yesterday on the highway in traffic the coolant temp was again at 215 and the oil was at 230.
The cooling system was flushed last year, the radiator was removed and the debris was cleaned off it, water pump is fine, and both fans kick on. Oh, and it runs a 160 degree thermostat.
The only thought I have is the fans seem to have more than one speed. Could it be one of them isn't kicking into "high gear" when it needs to?
What kind of temps are you guys running in similar ambient temperatures?
It has been consistently about 90 degrees everyday as of late. I just was letting my car idle to see how high the temps would climb earlier today. 90 degrees ambient temp, coolant was at 215 and oil temp was at 219! A/C was set at 5. Yesterday on the highway in traffic the coolant temp was again at 215 and the oil was at 230.
The cooling system was flushed last year, the radiator was removed and the debris was cleaned off it, water pump is fine, and both fans kick on. Oh, and it runs a 160 degree thermostat.
The only thought I have is the fans seem to have more than one speed. Could it be one of them isn't kicking into "high gear" when it needs to?
What kind of temps are you guys running in similar ambient temperatures?
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Those temps are normal. However, you may want to check for air in the system by backing out the bleed screw a few turns while the engine idles until you get a fine mist of coolant only. I think that the '96 fans will switch to high with the AC on. That should be an easy test.
Thread Starter
Burning Brakes
Joined: Mar 2008
Posts: 1,073
Likes: 8
From: Houston TX
Thanks, I will try that. The thing is, I don't remember it running this hot last summer and my roomate has an LT4 that was running 15 degrees cooler. We were sitting next to each other in traffic.
Thread Starter
Burning Brakes
Joined: Mar 2008
Posts: 1,073
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From: Houston TX
Team Owner
Joined: Oct 2004
Posts: 81,241
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From: altered state
St. Jude Donor '05
Those things are designed to run hot as hell its unnerving seeing the temp gauge almost pegged. Emissions thing I suppose not much room for error though.
Have the fans reprogrammed no reason an engine HAS to run that warm.
Have the fans reprogrammed no reason an engine HAS to run that warm.
Team Owner
Joined: Aug 2005
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From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
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St. Jude Donor '09 thru '20
I just replaced my 95 Rad with a Dewitt. The factory rad (not the shroud) was trashed full with dirt and all other things you can imagine.
Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
Our cooling system on LT-1's are quite simple. The problem, if there is a problem can only be one of several things:
A clean radiator
A good water pump
A good pressure cap
A good thermostat
Clean mix of distilled water and anti-freeze
Good hoses, top and bottom
Thats about it.
A clean radiator
A good water pump
A good pressure cap
A good thermostat
Clean mix of distilled water and anti-freeze
Good hoses, top and bottom
Thats about it.
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Burning Brakes
Joined: Oct 2009
Posts: 773
Likes: 2
From: Minneapolis MN
My 94 auto runs hot too.My fan turns on at 228 degrees.It goes up to 235 when stopped & idling for awhile.I turn on heater which brings temps down to 220 degrees.It gets pretty damn hot inside the car doing that through.I also have a 160 degree thermostat.A Dewitts radiator is my next mod as it allows the car to run 20-30 degrees cooler from what I read.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
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From: Palmdale CA
Thread Starter
Burning Brakes
Joined: Mar 2008
Posts: 1,073
Likes: 8
From: Houston TX
My 94 auto runs hot too.My fan turns on at 228 degrees.It goes up to 235 when stopped & idling for awhile.I turn on heater which brings temps down to 220 degrees.It gets pretty damn hot inside the car doing that through.I also have a 160 degree thermostat.A Dewitts radiator is my next mod as it allows the car to run 20-30 degrees cooler from what I read.
How much for a Dewitt's? Sounds like a worthwhile mod.
Burning Brakes
Joined: Oct 2009
Posts: 773
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From: Minneapolis MN
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
The fans are coming on at the correct temp(228 degrees) but even when the fan is on the temps still creep up.Sometimes up to 240 degrees.It happened one time.Now anytime the temp gets to 230-235 I turn on the heater which brings temps down quickly.Is anyone elses Lt-1 running like this in hot weather?Sorry to hijack
So both times it was a tiny leak that was, I think, letting air in durring the cool down cycle.
Burning Brakes
Joined: Oct 2009
Posts: 773
Likes: 2
From: Minneapolis MN
My '94 did exactly what you describe twice. Once it was due to a pin hole in the metal T fitting in the heater hose. The other leg of that T was the run to the passenger side of the throttle body. The second time was when the water pump was weeping out the weep hole.
So both times it was a tiny leak that was, I think, letting air in durring the cool down cycle.
So both times it was a tiny leak that was, I think, letting air in durring the cool down cycle.
I going to throughly check my cooling system,clean condenser & radiator,replace my "radiator" cap,& bleed my cooling system again.Thanks.Anyone else?
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
I am very sure that you will find that your a/c condenser and your radiator have debris in them and cleaning them will make a big difference in your coolant temperatures. Also, 235 F will harm absolutely nothing in your engine and is nothing to be alarmed about. GM says to shut the engine off at 260 F and let it cool down. I am sure they say this because 15 psi 50% antifreeze boils at 265 F and boiling coolant will damage an engine, in particular, the heads. Also keep in mind that the higher temp your coolant is, the more heat it can get rid of, this means that it gets increasingly difficult for your coolant to increase any more in temperature. At 235 F, your 160 thermostat has been wide open long before 235 and it doesn't do anything for your engine cooling, it was a waste of money and effort. You might as well not even have a thermostat in your engine. Its your radiator that gets rid of heat, not the thermostat.
Burning Brakes
Joined: Oct 2009
Posts: 773
Likes: 2
From: Minneapolis MN
I am very sure that you will find that your a/c condenser and your radiator have debris in them and cleaning them will make a big difference in your coolant temperatures. Also, 235 F will harm absolutely nothing in your engine and is nothing to be alarmed about. GM says to shut the engine off at 260 F and let it cool down. I am sure they say this because 15 psi 50% antifreeze boils at 265 F and boiling coolant will damage an engine, in particular, the heads. Also keep in mind that the higher temp your coolant is, the more heat it can get rid of, this means that it gets increasingly difficult for your coolant to increase any more in temperature. At 235 F, your 160 thermostat has been wide open long before 235 and it doesn't do anything for your engine cooling, it was a waste of money and effort. You might as well not even have a thermostat in your engine. Its your radiator that gets rid of heat, not the thermostat.
Last edited by 94vettelover2; May 24, 2010 at 09:17 PM.