I replaced my thermostat a while ago, as it seemed to be stuck at least part way open (car wouldnt come up to temp), so I took it apart today. The brass sleeve is molded into the thermostat housing and is stationary and has a rubber insert surrounded by wax. The metal plunger has a spike in the center that lets it slide back and forth over the brass sleeve to open and close the thermostat.

The interesting part is the wire leads (from the electrical plug), not entirely sure, but I'm wondering if they act as a heating element and melt the wax when the car gets up to temp, forcing the metal plunger to slide and open/close. If this is the case, I cant figure out what would have caused mine stopped working.

Thoughts?

 

Could it be a sensor rather than an actuator? It would tell the DME on the t-stats heating/cooling cycle. IIRC OBDII cars need to know when they over cool for too long for emissions reasons.

Without a heating element, and high-current wires I can't picture it really being a heater.

 

There *is* such a thing as a wax motor. It uses a heater to expand wax to move something. My old Triumph TR7 had one as part of the auto-choke functionality on the carbs.

http://en.wikipedia.org/wiki/Wax_motor
Not sure if that's what this is in the thermostat, but it's a possibility at least.

 

You are correct. They use that heating element to help open the thermostat. That is how MINI was able to vary coolant temps with sport button on the later N18's and how Manic is able to change the target coolant temps on their tunes. The ecu also monitors that heating element and it causes a check engine light when it goes bad.

 

Lol, just came here to post the same after some digging. I guess this could help explain the rapid cooling in sport mode.

Some good info here - http://www.bimmerfest.com/forums/sho...d.php?t=508605

I had a talk with a friend about his e46 a while back with the same setup.

 

Interesting, an electric version of the original wax and spring thermostat.

Wonder what caused mine to fail. The car wouldnt come up to temp, just stayed around 180-190 most of the time, only getting up to temp when it was 95+ degrees outside. But once it got up to the 218-220F mark, I could turn the HVAC fan up to high and the temp would drop like it should.

In fact, this morning, with a new thermostat, I noticed it only got up to about 205, but no higher, it was in the low 70s outside. Not sure what could cause the car not to get up to temp if not the thermostat.

 

Took the Mini out for a drive this morning, it was about 70 degrees outside, and after 10-15 mins of driving, the car was still only at about 180F and it threw the P0128 code for coolant temp being lower than it should (its not the temp sensor either). I cleared the code and kept driving for nearly 30 minutes and after a lot of stop and go driving it got up to 205F, but once I was on the freeway, it dropped back down to around 190-195F. It didnt throw the code a 2nd time, but the car is still not coming up to temp, despite the new OEM thermostat.

Am I just missing something obvious here? Is there any other non-OEM thermostats out there yet?

I'm about ready to just stick some cardboard in front of the radiator...cannot wait to get rid of this wonderfully handling POS.

 

This is probably a noob question, but why would the sport button make the engine run at cooler temps? What's the advantage there? Why not run the engine at the cooler temps all the time? It seems reasonable that cooler temps are better for an engine (longevity and performance) so why not hit them all the time...

Thanks in advance to those that reply.

 

Emissions , period. Lower emissions at higher temps. I ran my Trans Am at 165 24/7

 

Do you mean less carbon footprint? Or am I missing something here...

 

colder coolant = colder engine = richer running engine = more bad stuff comes out of the tailpipe. EPA/CARB stuff.

 

= more power ( with lower chances of going BANG )

 

Interesting, I'm having the opposite problem on my classic Mini, I'd love to get it to run 180-190, but it keeps climbing (on the highway) to over 200!

 

I'll trade you!