Overheats Then Drops To Operating Temperature
 

As the title says, my 92 k1500 w/ stock 350 overheats then drops back down to operating temperature. I've installed two aftermarket gauges and replaced the sending unit several times, always it goes to 260 turning on the check engine light, then i assume once the thermostat opens, the temperature plummets to 210, or, depending on the thermostat temperature i chose, as low as 140ish. I've replaced the thermostat several times also, but always stuck with Oreilly brand (garbage I'm starting to believe). Has anybody experienced this our have any insight what is causing it and/or what can be done took remedy it. I'm selling it to get another square and i just want it fixed so the next owner wont have this issue.

Oh yea and with no thermostat, it doesn't even get close to warm, which is proper...thankfully
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Re: Overheats Then Drops To Operating Temperature
 

I would put a Stant 195 degree thermostat in it. I believe the NAPA brand T-stats are made by Stant.

If the head gaskets are starting to leak it can push a little air into the cooling system. The air will go to the top. When you start it cold, if there is a air bubble at the thermostat rather then water, the thermostat will not open until the engine gets overheated.

If you want to try something, take any brand 195 degree thermostat and drill a small hole in it so air bubbles do not get trapped at the thermostat. This may take care of the problem you are experiencing, but you should test to see if the head gaskets are starting to leak.

Re: Overheats Then Drops To Operating Temperature
 

It's funny you mention that because it just so happens that there is a small trickle of coolant on the back of the driver's side head, didn't notice it till i saw a small wet spot under there. That and I just noticed the weep hole on the water pump leaks when running cold.

Re: Overheats Then Drops To Operating Temperature
 

Drilled a small hole in the failsafe 180 I've got in it, climbed to roughly 170-180 and dropped and held 140-150. I'll have the heads milled and checked, that way I know there's no warpage or any cracks (may as well right?). Then replace the water pump, and get a stant thermostat for grins