O-Ring to stop leak at temperature sensor?

Manolito · 02-08-2009, 08:53 PM

Found water leak in wife's 330. The water is coming up around the O-ring on the temperature sensor. The sensor seems to slide in very easily, as though the O-ring is not as 'fat' as it should be.

Anyone fixed this before and know what O-ring will work better?

Thanks.

Manolito · 11:03 AM

The O-ring from a fuel injector that I tried was just a bit too fat. I could not press the sensor back down in the hole.

I think have searched every size chart on the web. Standard inch-unit sizes will not fit, not even the military or aerospace specs.

That leaves us with metric O-rings.

I think that the original was a M3x8
The Bosch fuel injector O-ring is an M3.5x8

So the choice is -
1) Buy M3x8 and replace it if/when it shrinks like the original did.
2) Find a very soft (softer than #70) M3.5x8 and force it in.
3) Wrap Teflon tape around the original O-ring.

I have not yet found anyone who sells O-rings in small numbers retail who stocks either of the above sizes.
O-ring selections that are available in kits don't include either if these sizes.

I have sent out a few emails, but for a small lot like I would be buying, I doubt that any vendors will respond.

Most O-ring compounds are compatible with antifreeze. You just need one that is still pliable at sub-zero temperatures and will tolerate 220F or so. Buna N or Neoprene should be inexpensive and work fine.

IF I find one, I won't post a part number until I have actually tried it and confirmed that it works.

Rot 911 · 02-23-2009, 06:26 AM

I had the same problem when I replaced my hoses and didn't bother to replace the temperature sensor. I didn't want to be sidelined while I waited for a new sensor so I pulled the sensor and smeared a good layer of DOW silicon grease (has a consistency of very thick vaseline) around the o-ring. Popped it back in and no leaks! This was over 4 months ago.

Manolito · 02-23-2009, 08:55 PM

The only response I got from vendors was:

Allied Metrics Seals & Fasteners, Inc [alliedmetrics@nac.net]

Says they will sell M3x8 Viton O-rings
Pack of 100 for $85

I am not willing to spend $85 to try one out. If I was sure they would work well, I might try buying 100 and then post an ad offering to sell them to other e46 owners who sent me stamped self-addressed envelopes so I could recover my $$.