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Old 10-08-2018, 07:27 PM   #1
Dlan
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Join Date: Jul 2012
Location: Urbana Ohio
Posts: 8
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Default Overheating / thermostat testing questions

First a little history. I bought this car (1998 318ti) about 4 years ago. At that time, I replaced all the hoses, radiator, water pump, thermostat, cooling fan, fan switch, plastic connectors on the motor. The car run fine for a year or so until I was in a traffic tie up on a hot night. Long story short, the plastic connector to the heater core broke causing the motor to overheat. Removed the head, had it cut and the valves done. Reassembled the motor with the correct head gasket from BWW, and found there was no compression on #4 cylinder. Removed the head only to one of the lifters was stuck. (Add new lifters and another head gasket to the above list)

I worked through those issues and have the car running but now I find that it overheats. Using an aftermarket OBD temperature gauge, it will go past 250f (I shut it down at that point) Radiator bled while front of car was as high as my floor jack would go. Heater blows hot air, but the bottom radiator hose stays cool. Turning the heater fan on high will cool the motor for a few minutes then it goes back up. Not leaking any antifreeze.

All that seems to point at a thermostat stuck closed. I removed the thermostat and dropped in boiling water. Nothing happened. I received a new BWM t-stat today and decided to test first. Same thing, nothing happens.

Shouldn’t I be seeing the t-stat open? Both bad?

Any other thoughts on what could be going on?

I don’t want to give up on this car. The body and interior are mint. I’ve a ton of money into replacement parts. I'm just tired of throwing money at it and not being able to drive.
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