Weird over heating problem

[Shpatz]

Okay so I bought the truck on Thursday. Took it for a test drive, the temp gauge was really jumpy, but never went over 210. Messed with the wire after I got home and the temp gauge works great now. So the new issue is that it won't go over 210 for a mile or two after warming up, but it will go over at some point, but never past the next big hash mark, it usually gets to in between 210 and the next big hash mark. Then it'll go back down to around 180-195. The cycle repeats. This started happening last night, which is when it was worst. After tapping the t-stat housing with a hammer, it doesn't go as far as it did, but still past 210. Ruled out bad head gasket/cracked head. What could the problem be? I bought a new t-stat to be put in tomorrow, hoping that helps.

[Robyn]

Replace the stat with a 180F and then see what it does.

If it continues to jump all over then it's likely the gauge or sender.

You said you ruled out the head gaskets, how ????

Does the top radiator hose get extremely hard and or do you get any coolant blowing over the overflow in the fill tank???


KEEP US IN THE LOOP.

Missy

[Shpatz]

I bought a STANT 195* thermostat today. Atleast until I can get my hands on an AC Delco one. The temp gauge jumping was fixed by pushing the wire farther into the plug. The radiator hose is pretty squeezable. Nothing comes out of the overflow. Previous owner said he added coolant now and again, but the air bleed screw looks like it hasn't been touched in years. The thermostat gasket looks a bit old and corroded on the top. i'm taking it to my friend's (GM master tech with 20+ years exp.) shop in the morning to change the thermostat, examine the coolant temp sensor, and probably flush the whole system.