trick on getting thermostat to seal?

[remat457]

I went to put my thermostat back on and couldn't get it to seal, and that mount is very soft and broke.

I ordered one off of Ebay and have it now. Is there a trick to putting it back on?

Why are there two o-rings?

thanks!

[zekkfett]

Try using Vaseline or thick grease on the o-rings, it will help reassembly, and help to stop any leaks. Same process as the coolant tubes in the cylinder head. (If you have adjusted the valves before, you know how much of a pain these can be.)

[bmwpowere36m3]

I just went through this on my bike because the PO didn't change the coolant and the system was full of rust and build-up. The thermostat just sits in the lower housing, in a groove and the upper housing contains the o-ring (~ 45mm ID). I would make sure both surfaces are clean (I used a red scotch pad) and then tightened appropriately.

[jp]

mine has 2 o rings. Siamese style

[remat457]

Thanks guys! I got the replacement and popped it on. Much better!

[remat457]

Revisiting this as it still leaks a little bit even with the new old replacement thermostat -- looks like it is the upper vs lower body housing. I will try the suggestions above.

Thanks for the advice!

[Jet⚡Black]

It's probably the relief hole not being able to relieve itself; I guess I could have worded that better. Install the thermostat with the relief hole facing out away from the bike. As for the second o-ring I assume you know where it goes from taking it apart?

[remat457]

Thanks for the tip on the relief valve. The rings kind of fell out when I took it apart. What should the arrangement be? The replacement only had one...

[Jet⚡Black]

As far as the manual goes, there is just one o ring that goes in a slot in the cover, but that's it. If the o ring is the correct size and you have that slot for it that should keep it sealed, if torqued correctly. Does the replacement thermostat fit snug? If so then I wouldn't worry about o-ring two; if it didn't come stock with two o rings to my knowledge; so my guess is it was a PO's attempt to keep the thermostat from flopping in the housing like a spacer would that it was used to seal just stop movement...that's my best educated guess without seeing it.

[remat457]

Thanks for all the help everyone! I think this issue is resolved. Completely my fault - first over torqued the upper mount and broke it. I replaced it with another upper and neglected to move the o-ring. doh!

As for the the two little o-rings, I ended up using both side-by-side, it just seemed to make it seal better. Knocking on wood

[Jet⚡Black]

If the wood knocking fails some good high temp RTV should help it out.

[blacksmith]

The partzilla diagram shows 2, 22 mm o-rings at the radiator side of the thermostat. I know my bike is leaking handily, so at least one new o-ring is in order and a second may be placed on there for good measure. Hoping to save money and pick up a metric o-ring kit at the auto parts store.  

[sleepfaster]

I just changed the thermostat on mine and wound up having to buy multiple O-Rings for both the housing and the ones that connect the housing to the filler tube. If anyone needs either (or a set of all three), I'd rather mail them to you than continue storing them or throw them out. Drop me a line at [e-mail] if you want them.



Dennis