I have an 88 blazer, 5.7l. When I start it up, the engine begins to warm very quickly, and the guage buries into the red, and then the temp drops within range, then heats up again, etc...Sounds to me like a bad thermostat, but I just changed it a few years back. Does it definitely sound like a bad thermo, or maybe a faulty guage or sensor? Or, is there something else worng?

Thanks,

 

it sounds like you have a bad thermostat to me...thats what i woudl check first...its nice out, so take the t stat out altogether, and see if that fixes the issue.

 

my truck althogh not to that extreme is doing pretty much the same thing and i replaced the thermostat still no change but thats me. are you losing any coolant?

 

ok i think i might have found a leak finnaly on my truck i noticed today. after i drove it home from work today, i refilled the radiator let the truck cool off filled it again walked away for 30 minutes then filled it again all and all about half of a fresh jug. it seems to not want to be full always about 2 or 3 inches from the top of the radiator. after refilling it the third time i drove it for about 20 minutes and checked the engine, and on the passenger side i noticed a slight pool of coolant on top of the engine where the vlave cover and intake manifold meet. i checked the heater hose as best i could but could not see any moisture on it or where it goes in the engine. does this at all sound familiar to anyone?

 

I took the thermostat out and it runs cool and does not fluctuate. Obviously the thermostat I just put in a year and a half ago is a peice of crap. Had a lifetime guarantee??!! Like Chris Farley said, "I can S#!T in a box and stamp it guaranteed". That's about what I got. Anyway, I guess that's a lesson learned. Would it be OK to leave the thermostat out?

Thanks,

 

i wouldn't recomend it after all the thermostat is bascily in part a safety feature to keep your engine from over heating among other things

 

if it runs too cool, it will never get up to operating temperature and the oil won't flow as smoothly as it should. it could also gum up in cold weather causing a lot of problems. id put in a good thermostat.

 

get a fail safe thermostat that way when it does fail it will be in the open position.