Take the cap off and just let it run until the thermostat opens(the upper rad hose will get hot). Make sure the coolant is to the full level then use this tool to check for a bad head gasket. ANY color change means there is a leak. I tap into the vac line on the fuel pressure regulator.

 

thanks for the tip. will keep you posted.

 

Just tested with my new tester-3 times-ALL BLUE ALL THE TIME. Did notice the lower radiator hose collapsed (as well as the upper) while i was testing. Could it possibly be that the lower hose collapses the first time the t-stat opens because of the pump suction, causing my problem, then once the system has built up pressure from the heat, the lower stays open because of the pressure, hence no overheating till the engine is completely cooled off?

 

I drove this truck all day today. first thing this morning, gauge pegged. pulled over, turned off engine, waited 10 seconds or so, restarted, gauge needle fell like a rock, drove the rest of the day(app 30 miles around town, stop/start, here there), no problems whatsoever!

 

update-Installed a 180 t-stat, no problems of any kind since. live in midwest-kc area, 98 degree outside temps, runs like a sewing machine, good reading on gauge-about 1/3 of the way up.

 

Could be....more likely, the radiator hoses are weak and & cutting off or restricting currulation when in colapsed state. they shouldn't colaps

also the 180* T stat, is bit low...and may upset the running parameters a bit...run rich on cold starts. this may not be a real issue until colder weather hits, as it with run rich longer due to colder outside temps.

 

enriched-Thanks for the input, think I'll live with the 180 till cold weather, its not that big of a deal to switch out t/stats. thanks to all for the input.see ya down the road! (I'll probably be in a CHEVY, though!)

 

Hey first time here, I had the same problem it started when I changed the thermostat. What I did to fix was took the thermostat back out and drilled a 3/16ths hole in the thermostat outer rim that lets the water flow thru and haven't had any problems since.