Advice needed - LS3 running hot(??)

[Chad-1stGen]

I chased a hot running LS3 when I first got it in for a long time. Even sent the waterpump back to the manufacturer. Like you everyone suggested an air pocket. I did the usual tricks of jacking the front end up and filling from the upper radiator hose. None of that fully got the air out. I've since learned I can leave the car level and fill from the radiator like normal. The only thing I do is remove the steam vent hose (engine side) when filling the radiator. I leave it disconnected until water/coolant flows out and then hook it back up and top off the radiator.



For me, it's easy to know when there is air in an LS system. If the motor runs hot at low RPM but cools down at higher RPM then it's most likely air. For example my motor ran hot cruising down the freeway at 70mph in 6th gear at ~1,700 rpm. As soon as I downshifted to 4th and brought the RPM's way up it instantly cooled off.

good luck.