westsidebalto

Also checked the voltage using the menu. When the car is off it's drawing around 12v, but it's at 14v-14.1v after starting

westsidebalto

Took it to my indy. Pulled a different code this time, don't have the number, but it basically indicated a thermostat problem. He cleared that and the restraint code (though he didn't think he could clear that one, but it worked). I'm going to replace the thermostat and see if the CEL/SES comes back. Figured I should replace the ECTs since they are relatively cheap.

BimmerFan52

Good place to start.

Advise you stay with OE Wahler thermostat unit.
Last year when my alternator went bad I decided to do the water pump, thermostat, vent tube and belts at the same time. I first purchased an off-brand thermostat to save a few bucks but it didn't last a week before the heater coil burned out. Wahler unit has been rock solid.

westsidebalto

Saw you mention that on another thread. I ordered the OEM unit off ECS Tuning. They also had a Wahler, which was confusing (I thought the OEM was also a Wahler). An ECS salesperson advised against all MTC parts due to quality issues.

I've driven it twice now and no new CELs or other warnings. And thanks again BimmerFan.

westsidebalto

So instead of going to Bimmerfest, I spend my Saturday replacing the thermostat, auxiliary fan switch, and temp sensor. Took about 5 hours, mostly because I'm slow, but more because I spent way too much time getting the rear bolt off on the thermostat. It was only mildly easier to get back on.

The temp sensors were easy and I would recommend that anybody who drains their coolant for any reason replace them. Coolant flush was relatively easy too.

So far no codes have been thrown. I'll check again tomorrow for leaks and take 'er for a longer drive and see how she runs.

Does anybody know how to visually diagnose my old thermostat to see if it was broken?

BimmerFan52

If the water was flowing too soon in your case, you would see the thermostat stuck open or partially open when you removed it from the thermostat housing.

Sometimes when you remove it from the housing it will snap closed and you will never really know.

Also, contrary to good practice in controlled experiments, you changed three things at once (thermostat and two temperature sensors) so you may never know definitively which component it was. But it certainly wouldn't be worth draining and filling the coolant three times just to know which part it was.

If you have solved your problem with a few inexpensive parts and five hours of time thank the patron saint of DIY, call it a wrap and go give the beast an ole fashion Italian tune-up!