Engine overheat?, Diagnose this for me! Options

[gts4]

Hey. I drive a 94 gts. Basically, there appears to be a small oil leak, and I had rad blow on me. I replaced it, but my temp gauge tends to redline after 45 min of driving. Sometimes, it stays high, then dips down to 40%. It goes up and down.

It seems to go up when I downshift and hold it at 4-5k rpm.


Other times, it just moves by itself. Any ideas? Thanks!

Update. Found an oil leak on the valve cover gasket. Will fix it this week. Will check the thermostat after the leak is fixed.

Edit: I'm having another issue. The celica won't turn over. After shampooing and pressure washing the engine yesterday, my celica would stall at a red light. I barely got it going again, but made it home. It was turning over and started after 3 tries. This morning, it turns over and chugs without starting. What's the issue? Did I flood anything? Should I check the distributor?
Solved the starting issue! Distributor was fine. Switched to iridium spark plugs. Starts better than a new car
Thanks everyone!

This post has been edited by gts4: Feb 9, 2012 - 12:35 PM

[Galcobar]

Thermostat's fairly easy to test, it's just that it means you drain half the coolant out to get at it. Given a thermostat is US$15 even from Toyota (via 1sttoyotaparts.com or Lithia Toyota; I would not buy any aftermarket thermostat, except perhaps for a Stant) and involves only a couple of nuts (or five if you have to remove the AC compressor) it's an easy fix. That said, it's even easier to check the condition of the coolant first.

Milky = oil and water mixing, blown HG. If it's clear, check that the radiator cap is working -- the reservoir bottle should fill as the temperature and pressure in the cooling system increases. After that, you're probably looking at a replacement thermostat; test that by feeling the coolant hoses. A cold hose indicates a lack of circulation, which points back to your thermostat or your water pump. If you have a circulation issue, hope that it's your thermostat.