Hi Guys,

I recently purchased a '94 S10 Tahoe. When I looked under the hood I saw that the owner had bypassed the heater core with a piece of copper pipe. I know this is a good quick fix, but with bad weather it's not feasible to keep it that way. I replaced the heater core today, but I'm still getting hot engine coolant spikes every so often. Anybody know why it's doing that?

 

You may have air trapped in the coolant system. Raise the front end (passengeer side slightly higher) and run it up to operating temp with the radiator cap off until the bubbles stop. Let the engine cool down, add coolant as needed, and repeat the process.