This part has undergone an instream revision recently.
It opens @ 79 Deg C as previous.
This "new, revised " unit services other BMW vehicles & Volvo.
I am personally unhappy with the design change & have recorded my
concerns with BMW techinical.
Despite providing dimensional evidence & fitment data in the S38 B36/ B38
that confirms its unsuitability for use in this range of vehicles due
coolant bypass when cold & leakage from the thermostat housing & cover
assemby, the received reply from BMW UK Technical was :
"We sell 56 a year with no problems reported since the change to the original
We cannot investigate a part because it looks different "
"There is also the possiblility that you will need to replace the housing with a
later version when undertaking the thermostat change."
(That 56 quantity cover the other BMW vehicle variants inc S62 engine that does not remotely
resemble our application)
So we are clear.
The original part is made by Behr Thompson.
It sealing ring is an integrated moulding with the metal thermostat spider.
The "updated revised" part is made "an other".
The sealing ring is not integrated, it is a simple lip seal that does not
seal radially or under compression adequately in our vehicle application.
The sealing ring that the body of the thermostat locates into has not
So, that leaves a 0.125mm radially discrepancy between sealing ring & body.
I have fitted this part in its current configuration from an aftermarket supplier
in a quest avoid the massive cost of BMW thermostats.
In two vehicles including my own, both have leaked.
I have also tried other similar units from Gates & Valeo that open @ 79 Deg C
& both have similar dimensional discrepancies despite assurance from the
suppliers that they will work.
Since the above, I have gone back to BMW for these parts due to their
suitability to our vehicle application.
If this is BMW's answer to a valid techinical concern, it certainly mirrors their
general lack of concern for keeping supply of parts available & at sensible cost.
Hope this helps when you buy a stat & find it leaks.
You will end up gunging the cover & housing faces with sealant
which was supposed to metal to metal.
But you won't prevent the internal leak path around the thermostat internally.