Thermostat and O-Ring Order

[thehackmechanic]

While I had my cooling system open from the heater bypass exercise, I wanted to put the 80 degree thermostat back in (with the Mark Preisendorf triple-core radiator installed, with the 71 degree thermostat, it only runs 1/3 of the way up the gauge).

I've made this mistake before, and I just wasted hours by making it again.

Note to myself and those who follow:

--When installing the thermostat, the O-ring DOES NOT GO between the thermostat and the housing, even if you think it does because the circular groove in the housing holds the o-ring perfectly. THE PICTURE ON THE LEFT IS WRONG AND CAUSES SYSTEM TO LEAK LIKE YOU AFTER DRINKING 5 BEERS ON A SATURDAY NIGHT.

--The O-ring goes between the thermostat and the cover. This is how the Haynes manual shows it. THE PICTURE ON THE RIGHT IS CORRECT, even if the thermostat doesn't want to balance and stay seated in that circular groove. You have to sort of slap it together, mush it all into position, and screw it in. If you're really paranoid that the thermostat is seated correctly, you can pull off the C-shaped hose and hold it in place from the back.

That is, unless someone tells me that I have it wrong.

:^)

--Rob

 

[sfdon]

It is remarkable that BMW manages to show it going together completely opposite
depending on the vintage...

I just made the same mistake last week!



http://www.realoem.com/bmw/showparts.do?model=3435&mospid=47811&btnr=11_2454&hg=17&fg=05


http://www.realoem.com/bmw/showparts.do?model=6941&mospid=47185&btnr=11_0695&hg=11&fg=35

 

[thehackmechanic]

Misery enjoys company

Don, you have no idea how much better that makes me feel, especially coming from a pro!

 

[BarryG]

Is this a stock motor Stat? not a b34 or b35?

Thanks
B

 

[thehackmechanic]

Barry, it's a bit of a Frankenmotor, a 3.2 from a 533i but with an L-Jetronic injection system from an E12 528i. The thermostat housing was from the 528i. It uses the thermostat on the left in the pic, which is the "newer of the old style." The "older of the old style" is on the right in the pic. But, from what I can tell, both of these thermostats need the O-ring between the thermostat and the cover, not between the thermostat and the housing.

 

[BarryG]

Rob
The last time Don and I saw each other he looked at my thermostat housing which is stamped 86, and said I need to match the year of the housing to the thermostat, of corse thats a no brainer.
So are all housing the same? as in the depth of the bottom sealing ring of the stat... and the 2 O ring flanges.
Here s mine for my 1986 b34... The O ring flange is the opposite of yours.

Just thinking and learning.
Thanks

 

[sfdon]

There is a whole story here about time and stamps and letter A's and t-stat covers and October of 1985 and gaskets that are discontinued and o-rings that go on one side and then the other and discontinued bleeder screws and cars that won't warm up and cars that overheat in minutes.....
but it's late and we will talk about it another day.

 

[hans3]

I'm hesitant to believe that the OEM BMW parts diagrams are incorrect in regards to thermo gasket placement. As referenced by others and Sfdon above, it likely changes by year and thermo-housing design. The only evidence of a "leaking" themostat gasket would be a much longer warm-up period. Incorrect gasket placement should not induce overheating, as it would not prevent the thermo from opening. My 2800's thermo gasket is positioned per the parts diagram--aft of the thermostat in the groove. Warm-up period duration is normal vs. other cars.

 

[deQuincey]

I'm hesitant to believe that the OEM BMW parts diagrams are incorrect in regards to thermo gasket placement. As referenced by others and Sfdon above, it likely changes by year and thermo-housing design. The only evidence of a "leaking" themostat gasket would be a much longer warm-up period. Incorrect gasket placement should not induce overheating, as it would not prevent the thermo from opening. My 2800's thermo gasket is positioned per the parts diagram--aft of the thermostat in the groove. Warm-up period duration is normal vs. other cars.

will not discuss on this topic because my thermostat setup is a newer version, but i will say that BMW diagrams can be incorrect, i have the proof of this in the one that represents the new version of the radiator fan setup, it is wrong !

 

[sfdon]

There are all sorts of Errata in the thousands of pictures produced by BMW over the years.
My favorite was the vacuum diagrams for the 745i turbo to distributor - backwards on retard and advance.