this is on a 08' silverado...long story short...truck had a 08' vmax 6.0 that overheated and mest up a piston to begin with.....so we installed my old 4.8 in it...got it started and running fine!!but the damm thing gets hot.we have already tried another thermostat and still gets hot....it starts boiling and throwin the water out the reservoir,like its not circulating.it cant be the motor cuz i never had problems with it before.
any ideas tips? BIG *** air pocket maybe?we used the water pump from the vmax on the 4.8 if that matters

 

If it was me I would have changed the water pump when putting in the 4.8 if the 6 died from overheating.

 

Are the fans coming on?

 

yea we should have got a new pump.....yes the fans do come on

 

Are you getting air across the radiator, in other words, is there a bunch of leaves and junk in between the radiator and condenser? Of course make sure that all of the air pockets are out of the system.

 

also make sure there is no rust deposits and buildup in ANY of your hoses, my buddies 01 5.3 overheated, shop took it all apart and put it back together and it still did it, turned out to be a clogged hose

 

is the belt on right? not saying you messed up or anything...but i put mine on backwards but noticed before i cranked it.

 

make sure all the air is out of the system,, i just went through this with my brothers truck, put new thermostat and water pump and it still did the same..... it ended up being the radiator that was clogged/plugged!!!! he took it to get it cleaned out and it runs like a champ now!

 

yea we tried about 20 times to get that air out and nothing,,,we are thinking its the damm radiator as well....thank yall for the input..we will find out monday after a good flush

 

Yeah i jacked with his truck like 3-4days thinking it was air, his is a 2000 though so was probably expected since it also had only water and no antifreeze when he bought it