Engine Runs Cold

[2K_Silverado]

New guy here, of course with a problem...

I have a 2000 Silverado 1500 ECSB that had a 4.8 and MG5 5-speed. At 252k on the clock it was time to replace the running gear with an LS3 (430HP), Tremec Magnum and 4.56 gears. This setup has about 500 miles on it to date.

I have an issue with the cooling system which consists of a Be Cool 2-core radiator, a 187 thermostat and a pair of 13" electric fans. All parts are new. If I let the engine idle in the garage it will get up to temp, the fans turn on at 205, the temp goes down, the fans turn off at 195, rinse and repeat. So far, so good.

Well, when I go for a drive, and depending on the ambient air temp, the engine temp drops down low. So at, say, 66 degrees air temp, the engine will run at 150 or so. If the air temp is in the 40s, the engine will run about 130.

According to my factory manual, coolant always flows through the overflow tank by design (also the heater core). And it does. From there it flows into the heater hose Y and back into the water pump behind the thermostat.

The only way coolant can enter the tank is to flow through the radiator and out the overflow tube. So it seems to me that coolant is bypassing the thermostat, flowing through the radiator and therefore overcooling. There is no air in the system.

I called the guys at Be Cool and the guy told me to put a piece of cardboard in front of the radiator because their radiators are "too efficient", so they say. That makes no sense to me since the radiator I have is the one they recommend (P/N 80102). It's also a major hassle and not an appropriate fix in my opinion.

I've tested the thermostat in a pot of water on the stove with a candy thermometer. It appears that it opens and closes as it should. I have another thermostat on the bench to swap in just in case. I also have a stock 1-core radiator coming in a couple of days in case I need it.

Is there something I'm missing here? I've agonized over this for days (and done much searching) trying to figure out where the problem lies. I'm hoping one of you guys can help me out.

[2K_Silverado]

Nevermind, I fixed it.

[farmtruc]

was it a too cold of a tstat, mine does this but i don't mind.

[2K_Silverado]

Nope, stat is the stock 187, although I did replace it while I had the coolant drained. I tested the old and new stats in boiling water and they both behaved identically. I believe the real fix was replacing the Be Cool 2-row rad with a stock 1-row. Now it runs in the mid-190s, right where it should. I'll see what happens in the heat of summer, but I think I'll be fine.

My takeaway is this - if you don't have an overheating problem, keep the stock rad. Stock rads are relatively cheap, Be Cool not so much...