thermostat, overheating, refilling coolant?

[carthings]

Manual instructions says to disconnect negative cable for safety, rock back and forth checking for freeplay or looseness - look for leaks from clutch fan. fan blades should turn freely by hand when cold. When the engine is warm the fan should have drag ,if it is warm and turns easily it needs replaced, when checking fan remove the negative battery cable for safety.

 

[dsfii93sport]

Any one want this truck for $500, I think I'm ready to trash it... Engine started running strange...

 

[89chevy2500]

Any one want this truck for $500, I think I'm ready to trash it... Engine started running strange...

dang... im so glad i sold my X

 

[Sscolax]

My 85 Bronco II, which sports a 91 4.0L, suddenly started doing the same thing when out on a road trip over the weekend. My mechanical gauge would show the temp spike up to 230-240, then back down to 190 every few minutes. Keeping it revved higher seemed to make it run a bit cooler. Lost coolant through the overflow, and it never pulled any back into the engine after it was shut off. The engine was rebuilt 2 years ago and has 30K miles on it. Everything was new at the time of rebuild: thermostat, radiator, hoses, water pump, fan clutch, and even new (not rebuilt) heads. I just pulled the heads yesterday and found a major crack running across the combustion chambers of cylinders 5 and 6. Today the machine shop found a crack in the other head when they magnafluxed it.

 

[doonze]

crap, mine is doing the same up and down thing.... I really hope it's not a head crack, or gaskets even. Shoot, only had the truck 2 days. Mine just bounces around from M to L all the time, just kind of up and down and up and down, never really settles down. Hmmmmm.... anyone else have an ideas? Only other thing I can think of is fan clutch.

 

[marragtop]

I'd start by replacing the t-stat. If it sticks closed it will overheat potentially blow head gaskets and damage the heads.