ChevyROB

Hi, I'm new to this site and really need some help with my truck. I have a 2001 ex-eab short bed chevy with a 5.3 vortec. It was over flowing reservoir and then got hot. I have put a new radiator on it new water pump and thermostat purged all air out of system many times and checked the thermostat many times checked compression and it had 190 psi on all cylinders. So I thought well it can't be a bad head gasket cause such good compression so I thought it had to be a cracked head pulled the heads had them checked and they checked good for pressure test. So now I'm lost I've worked on alot of things and have never been this stumped I can usually figure it out but this one really gets to me so any helpful input would be awesome. Thanks for your insight in advance guys.
You could drive the truck about 2 miles off cold start and it would get hot and go into reduced power mode.

pipedream

If the problem doesn't happen just sitting there idling and only happens when the engine is under a load try checking the clutch fan. make sure there is sufficient drag when you try to spin it. It should move very much at all. If it seems loose put a new on it or change over to a solid fan assembly. You may not be getting enough air cooling through the radiator also check for anything that would restrict the air flow. Make sure the shroud assembly is in place. Good luck...

ChevyROB

I appriciate the advice man. I finally figured it out though. Had a some what loose head bolt right by a water jacket and the gasket looked a little funny between the water jacket and cylinder so put all new gaskets on it and ARP head bolts and still had a little trouble with it gettin hot made sure is was full of coolant and all the air was purged out. Engine tempature was 240 turned it off got out and my top radiator hose was cool to the touch of my Hand so I thought this isn't right at all so I squeezed around on it and the bottom hose waited for awhile tried it again and it's been workin like a dream ever since. So I guess the thermostat had stuck on me for a little bit but it was fine before but it had been setting untouched or started for about 5 months because it was working before I checked it about 4 different times. So my conclusion is that my head bolt either loosened off some or streched and it was letting exhaust blow through into my water jacket and cause it to over heat when under a load. Got it fixed and doing really good so far. I appriciate the advice on the shroud and fan though. Thanks for your time.