I'm putting a crate LS3/525 in my 79 vette. Started it up just recently and had a questions on the LS3 normal operating temperature (right now, just idling in my garage it can climb up to 230) and if there are any other procedures for purging the coolant system to get any air out of the heads.

Engine coolant temp idles around 220 and will slowly creep up to 230. If i rev up to about 2k the temp drops down to 205ish. Again the car is up on stands, the rear of engine looks slightly lower than the front). I'm running a 180* tstat. Radiator cap is slightly above the water pump outlet (for highest point). Aluminum radiator is about 5 years old and slightly larger than stock. I do have an overflow tank connected and fans are working. ECM is from gmpp tuned for the LS3/525 crate motor. I have the steam vents (front 2 only on ls3) routing back to a tee fitting on the water pump outlet hose going to the radiator.

Seems like there is some air/steam trapped in the block. Are there any other options for purging air or steam in heads? Any thoughts are appreciated.



Thanks,
Ryan

 

yea put a steam vent kit on it, guy on ebay has a nice kit not too expensive I bought some extra AN fittings because I had room/routing issues so with some extra fittings front and rear stean vents, I did not have any problems in the first place, but figured it couldn't hurt. and it didn't.

 

Ryan,

I have had really good luck with backfilling the cooling system through the steam vent tube. It is a little slow and tedious, but it always works like a charm.

I put on a 12" hose on the steam fitting, get a little funnel and just slowly start to add fluid. The funnel will be the highest point in the cooling system, so all air should be purged.

Also, the GMPP tune turns the fans on at 212 and off at 205. With your temperature levels the fans must be on constantly. You definitely don't want that!

I would also make sure that you have adequate fans on the radiator.

Andrew

 

Thanks for the replies. I was going to try the back fill method but, got tired of playing with it and ended up just buying a cooling system leak checker/air lock purge kit. It basically pulls a vacuum on the cooling system and then it'll fill up the system with no pockets. Worked great. Very easy and clean method.

I did notice the fans kick on around 205 (via bluetooth torq app) and after that the coolant temp stays around 185. Both the autometer gauge and torq app/ecm now read right about the same temp (no more 15 degree temp difference look he before which made me think it was airb trapped). I did end up putting a "160" tstat in from lengenfelter. I tested it on the stove top and it didn't start opening until 172. The stock tstat opened right around 186 which is accurate.

I'll get the fans temps adjusted later if need be.

thanks again

Ryan

 

that's great that you fixed it, but if you just would have put in rear steam vents it would have filled right away and you'd not have spent half the $ and you would have ELIMINATED ANY hot spots in the motor you already proved that there is no water flow in the back of your block.