Have rebuilt my Vortec v6 which had a rod knock and over heating issues. Took care of the rod knock but still having overheating issues. Have had the heads redone, was told that between 5 to 6 thousandths were shaved during resurfacing. Got the thing put together and wouldn't you know it is still over heating. Have racked my brain and just can't seem to figure this one out. Can someone please help before I roll this thing off a cliff. Would shoot it but in this day and time gotta save all the cash I can.

 

thermostat not opening? water pump broken? fan clutch bad? radiator fins clogged, no fan shroud. air bubble in system?

 

Yep, what he said. All of those will make your engine overheat.

 

did you replace the waterpump,stat,and rad during the rebuild? Might as well. Also,check your fan clutch. see if it has any resistance when you spin it. if its super loose,replace it.

 

All of those have been replaced.

 

i wonder if you just have a huge air pocket in your block, some chevy vans when i work on the block, waterpump, intake, etc i always drain the block cause the drain plug on the radiator is impossible to get at and the bottom radiator hose uses this big clip thing id rather not mess with.

anyways if you just fill up the radiator on these things with antifreeze it almost always over heats unless you bleed the system, antifreeze just doesnt seem to work its way in to the block. we have this vacuum attachment at work that you can stick into the neck of the radiator and it causes a vacuum in the system, then you put the tube into a bottle of anitfreeze, flip a lever and it just shoots the fluid into every corner of the cooling system, works everytime.

wonder if autozone or anyone rents those things

 

sounds like a huge air pocket to me somewhere, jack up the passenger side, take off the radiator cap and try burping the system until it gets to operating temp.

 

Take and remove your t stat temporaly and let your engine run for 5 minutes.This will remove any air bubbles if theres any.