Evo9... Accidentally hit rev limiter one night last weekend and 15 minutes later my car was running hot. Pulled over and checked coolant and both the radiator and reservoir were full. There was a small amount of coolant leaking from the bottom of the car, but that has since stopped. Let it cool, and made it home and drove it the next couple days without issue. My buddies dad is a mechanic for mitsu, and he drove it into work and did a pressure test on the cooling system cool, and hot and said it checked out fine. He said my ecu isnt telling the cooling fan to turn on so he wired a temporary bypass to manually turn it on while we wait on the ecu and said he had no trouble with it. So i picked it up and 10 minutes later it was overheating, and will only run at normal temperature while either idling or driving quickly, but in parking lot, or traffic it starts creeping up. Do you guys think its the head gasket? Brand new radiator and coolant btw.

 

pull the dipstick and see if you have wide sludge forming in the oil pan

 

Can you log the coolant temperature through Evoscan and confirm the ECU temps is matching what is showing on the cluster?... Report back what your ecu is reading when its over heating if you can.

 

did that already and didnt see anything

 

The radiator fan is variable speed and as I recall the ECU tells the fan controller what speed to run. So, I'm thinking a switch wouldn't do the same.

 

No, but the switch would just make it turn on at 100% only.
Im curious how he figured the ecu wasn't commanding the fan to turn on? The fan isn't necessarily on all the time, I think it starts to come on when coolant temps reach 200 or 205 deg, or somewhere near there anyhow. This is the case with most cars, not just 4g63s btw.

 

sounds like either the fan isnt kicking on or your thermostat is sticking. Thermostats are cheap try replacing it.

 

Check your coolant lines. I had an insidious leak from the expansion tank to turbo. Everything else was full except the expansion tank. Seemed like a thermostat problem, but once I figured it out, super easy fix. Line was rubbing and just wore a small hole. Good luck, hope this helps!

 

I think you are talking about an experience with a vehicle with a different type of cooling system. Evos, however, are known for getting pinhole leaks in the smaller hoses like the ones going to the turbo.

To the OP, head gasket leaks usually occur with the head lifting a WOT. Otherwise you can usually drive for days or weeks without a problem. The usual leak is combustion gases to cooling system. The gases in the engine push coolant to the jug and when it gets full, onto the ground.

So, I'd suggest you watch your driving habits and see if the problem matches the pattern I've mentioned above.

 

Different vehicle, same exact place and issue. The coolant line to the turbo...

To the OP. I'd check that line...