Hi,

I have an LS1 with a 4L60E in my Cobra that I have just finished rebuilding. I've read a lot of posts stating that it's not unusual for these engines to get up to 220 deg. F coolant temperature when running.

So my engine is getting up to that temperature (around 220~225) after about 15~20 mins of running. The fans seem to cut in at just over 220 deg F and then the engine will drop back to a little under 220 deg before the fan cut off again. On warmer days I've noticed it will get to just under 230 deg before the fans bring it back to just under 225. This cycle will repeat but the temp doesn't seem to get over around 228 deg F at any stage.

Just a little more on the setup: I am using a GT40 radiator due to lack of space under the hood. I've had to mount it at an angle (sloping back) due to the height restrictions. It measures 730mm (28.7") x 320mm (12.6") x 55mm (2.16"). Its a 3 row aluminium radiator which I mounted upside down from the normal way its mounted in a GT40, so both inlet and outlet are at the top of the rad. I've also installed a high flow water pump which claims to pump at +30% over a normal pump. I've also installed a Mr Filter high performance thermostat which opens at 180 deg F. I've installed a shroud around the rad so that airflow is more directed into the rad rather than flowing over the top.

So first question is based on the coolant temperatures I'm seeing, do I have a problem or are these numbers to be expected for an LS1? So far the ambient temperature I've run it in has been no higher than around 77 deg F. Temperature here in summer can get up to around 100 deg F. Will I have a problem at these temperatures ?

If the engine is running too hot, what else can I do to cool it down?

Advise appreciated.

Cheers,
Greg

 

You will need to use tuning software to change the temperature at which your fans turn on. GM actually "dummied" the gauge reading for coolant temperature on many ls1 vehicles to prevent people from complaining of overheating. The temps you are seeing are normal, but that does not mean any of us have to like running that hot.

 

You can force the low speed fan to come on at 185 deg. F by turning on the AC. Not sure what's involved in doing that - I can see that their is a pin on the PCM called "AC Enable". Would activating that simulate AC on?

Also, I think the fan would be running all the time at 185 deg. Maybe better to find some tuning software to change the trip temp of the fan to something like 210 deg.
Any recommendations for free tuning software?

Cheers,
Greg

 

At 220-plus temps, the fans are a little late to the party.
Stock thermostat is 187.
The fans should come on about 200-205 and shut off around 190-195.

 

When you say "normal", you referring to factory stock?

Pretty sure my stock tune for 1999 Trans Am has the fan 2 coming on at 234 and off at 227, fan 1 somewhat earler. Note that this isn't just one fan and the other, it's low speed and then high speed in fbodies The factory tune lets the engine run hotter than you'd expect. I've set mine lower like how G Atsma describes but I don't think I'd call your temps "a problem". Just my opinion.

IMO you want at least 200, engine oil is designed to be most efficient around 200. You want to occasionally hit 212 IMO to boil off moisture/impurities.

You could go lower for better performance but if you are asking normal- aka factory then those I think are your numbers.

I remember reading that those with 160 degree thermostats are actually causing slightly more wear on the engine because the oil needs to be hotter than that to be most efficient. But I could be wrong.

 

So the fans come on at 220 degrees and it runs 220 to 225 degrees?

You are aware that the fans remove the heat from the radiator? Why would it not run at the fan setting?

You only have a problem if you turn the fans on at a lower setting and it runs hotter than that setting.

 

I agree on the 187° stat. BUT, that is where it starts opening. My guess is it's not fully open until 195°-200°. I may be wrong, but I don’t think so. I have a C5 Corvette, so apples to melons, but the stock C5 fans arent programmed to activate on low speed until around 220°, and high speed doesnt happen until around 235°. Maybe Fbody cars are programmed differently, IDK. I have mine programmed to activate high speed at 196°, off at 190°.....