duckdivin

Heres the problem I have changed the thermostat ,water pump, both sensors engine and coolant , new hoses, new dist and wiring, tested the thermostat it opens at 195 to 200 , new head gasket ( all new gaskets from head up ) Chevy told me operating temp should be around 195 to 212 . O I have flushed rad. my gauge has worked fine chevy told me its mostly not my gauge on inside . Heres Question with thermostat in my inside gauge jumps to 260 then thermosat opens and cools to 240 and stays there , but if i take out thermostat my gauge reads 195 to 200 . i have heat but i keep losing coolant i think its dropping from relief from water pump for pressure . I have replaced evrything i could .Is there a chance my heater core could be causeing all this mess for being clogged to some degree . O ya one more thing I put one of those laser temp tools and checked block it read 220 and my intake read 215 . I am completly lost on this and so are my freinds ???

cam3439

It could be the wrong thermostat or a defective one that isn't fully opening and restricting flow of coolant. It shouldn't open up at 260, that is way too high. Have you tried taking out the heater core from the system? I would take both lines off of the heater core from the fire wall, and connect them directly together to see if the heater core is causing the problem. You could be loosing coolant since the water is getting too hot. It could be flowing out of the overflow hose, which is usually located on the reservoir, or through a leak. You might have caused one with your temp going up to 260.

gmpartsguy

yeah im hip on the thermostat. where did you get it? ive seen tons of times where people try to save money and get an A/M thermo and its no good or opens at the wrong time. check temp at the block at one of the frease plugs, and make sure its reading the same there. just because you flushed your rad. doesnt mean its not still clogged. 15 years is a long time for stuff to build up in there. maybe your building a fossil inside your radiator. if the thermostat, or radiator isnt it than im lost man.

MDTAHOE

When does it overheat? sitting still? or while in motion?