What temp?
Race Director
Joined: Oct 2005
Posts: 11,776
Likes: 182
From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
Mine LT4 runs very hot at idle, pushing very close to the HOT hash marks on the analog guage which are nearly 240-250 deg F. I just changed the coolant and it makes only a little difference.
I need to know how HOT this stock setup can/should run, what is "normal" for these engines at idle and how to test the fan circuit? Never had any boil over, but am concerned about engine damage. When the car is moving it goes into the middle temp range of the coolant gauge, in the 200's. Oil never hot. My A/C does activate both fans, not just one, because primary fan does not seem to activate at all as far as I can tell.
I need to know how HOT this stock setup can/should run, what is "normal" for these engines at idle and how to test the fan circuit? Never had any boil over, but am concerned about engine damage. When the car is moving it goes into the middle temp range of the coolant gauge, in the 200's. Oil never hot. My A/C does activate both fans, not just one, because primary fan does not seem to activate at all as far as I can tell.
The LT4 has 2 fans, and they both come on at the same time. Either high or low speed. What is the temp your seeing on the digital gauge?
Without the A/C running, the fans will NOT come on until you see approx. 219 - 228
both fans on low at 219 F (off at 207 F)
both fans on high at 228 F (off at 214 F)
If your A/C is working as it should, turning on the A/C will also cause the fans to kick on. This is why the C4 will usually run cooling with the A/C on.
According to GM, TOO HOT would be 260.
If your cooling system is in good shape, you should never see it get over 235 - 240. (digital gauge). Remember, at 228 on the digital gauge the analog gauge will look like it's pegged. But look close, and you will see the needle just shy of the shaded area.
With the recommended coolant mixture, and factory pressure cap the coolant will not boil over until close to 261 F. (at sea level).
NOTE: Wanted to make it clear that the high temps (220 - 230 range) are only when sitting at a stoplight or not moving. At those times, there is little to no airflow through the radiator. That's why it gets hot up to the temp where the fans kick on.
When moving down the highway, your temps should be in the 194 - 197 range.
Last edited by RollaMo-LT4; Aug 28, 2007 at 10:45 PM. Reason: added note
Burning Brakes
Joined: Jan 2007
Posts: 1,117
Likes: 1
From: Central NJ
Just a thought, if your car was getting close to 235 or more, if you would shut the car off the temps would rise another 20 or so degrees, wouldnt it be better to open it up, and let the water pump do its job?
The pump pumps alot more at 5k rpm then at 1200 rpm, but it would only help if moving at least 15 mph.
Anyone else agree or disagree?
The pump pumps alot more at 5k rpm then at 1200 rpm, but it would only help if moving at least 15 mph.
Anyone else agree or disagree?
Melting Slicks
Joined: Oct 2004
Posts: 2,662
Likes: 8
From: Knoxville Tennessee
Have you removed your radiator and cleaned it and the condensor? This is a very common problem with our bottom feeders; leaves and other trash from the road gets sucked into the rad core. Mine was terrible. I replaced my rad with a DeWitts, it has twich the capacity of the stock radiator, and my temps never go above 195, even in 100 degree temps we have been having. I believe the extra capacity helps to regulate the temps. Good luck!
Bernie
Bernie
