Thermostat housing O-ring

[ac427]

I've been watching several YouTube videos on S54 water pump replacement.

Apparently the thermostat housing has an O-ring that is not available as a spare part. The only way to get a new one is to buy a new housing.

Has anyone measured this O-ring or found a replacement for it?

[Tbonem3]

Think it comes with the thermostat:

https://www.fcpeuro.com/products/bmw-thermostat-11531318274?ads_cmpid=352576039&ads_adid=229724073 19&ads_matchtype=&ads_network=g&ads_creative=8521 8 275839&utm_term=&ads_targetid=pla-85603299244&utm_campaign=&utm_source=adwords&utm_m edium=ppc&ttv=2&gad_source=1&gclid=CjwKCAjwqMO0BhA 8EiwAFTLgIM8jdN_S45dFYEQ1N6wonSKKq_Mx3KIvVpJRaYcqs b1mikfaxp7K-BoCa2cQAvD_BwE

Here are some individual ones, where ECS is saying BMW DOESN"T supply an oring with the thermostat:

https://www.ecstuning.com/BMW-E46-M3-S54_3.2L/Engine/Cooling/Thermostat/O-Ring/

[karter16]

Also available separately (note I'm not endorsing ECS tuning specifically, they just came up when I googled it)

https://www.ecstuning.com/BMW-E46-M3-S54_3.2L/Engine/Cooling/Thermostat/O-Ring/

[Stilt]

I've been watching several YouTube videos on S54 water pump replacement.

Apparently the thermostat housing has an O-ring that is not available as a spare part. The only way to get a new one is to buy a new housing.

Has anyone measured this O-ring or found a replacement for it?

Really, I never knew that; to be fair, I rarely ever from ecs/fcp; I buy all my parts via Worldpac and get them the same or the next day , which is super nice since the m3 is my daily.

If you really need a thermostat housing gasket, I have one right now that I thought I would need since I had dried coolant all over the bay (I pressumed I had a coolant leak and was going to replace all the gaskets b/c that's what I usually do lol), which turned out to be my rad having a hole in it.

[ac427]

Think it comes with the thermostat:

https://www.fcpeuro.com/products/bmw-thermostat-11531318274?ads_cmpid=352576039&ads_adid=229724073 19&ads_matchtype=&ads_network=g&ads_creative=8521 8 275839&utm_term=&ads_targetid=pla-85603299244&utm_campaign=&utm_source=adwords&utm_m edium=ppc&ttv=2&gad_source=1&gclid=CjwKCAjwqMO0BhA 8EiwAFTLgIM8jdN_S45dFYEQ1N6wonSKKq_Mx3KIvVpJRaYcqs b1mikfaxp7K-BoCa2cQAvD_BwE

Here are some individual ones, where ECS is saying BMW DOESN"T supply an oring with the thermostat:

https://www.ecstuning.com/BMW-E46-M3...mostat/O-Ring/

Thanks Mate but it is actually the O-ring for smaller diameter end for the thermostat, as shown here: https://youtu.be/JZs6DD8JUKY?t=532

[ac427]

Really, I never knew that; to be fair, I rarely ever from ecs/fcp; I buy all my parts via Worldpac and get them the same or the next day , which is super nice since the m3 is my daily.

If you really need a thermostat housing gasket, I have one right now that I thought I would need since I had dried coolant all over the bay (I pressumed I had a coolant leak and was going to replace all the gaskets b/c that's what I usually do lol), which turned out to be my rad having a hole in it.

That's very kind of you. I'm going to do some more research first but i may take you up on the offer.

[jayjaya29]

Is there actually an oring in there?

[George Hill]

Its not a o-ring, its a lip seal like a crank seal. BMW doesn't list the S54 separately.

This is a for an S62, same idea, maybe its the same part, IDK off the top of my head: 11531312287

[ac427]

Its not a o-ring, its a lip seal like a crank seal. BMW doesn't list the S54 separately.

This is a for an S62, same idea, maybe its the same part, IDK off the top of my head: 11531312287

Thanks for the part number George.

https://www.realoem.com/bmw/en/showparts?id=EJ11-EUR-12_1998_E52_BMW_Z8&diagId=11_5265#11531312287

It could be the same seal but the housing is definitely different.

[Bry5on]

It appears to be a carbon impregnated PTFE (Teflon) wiper seal. I wouldn’t expect much if any wear, although I did replace my tstat housing at 180k miles to rule this out as a failure mode. Pressing a thermostat into a new housing should feel noticeably more difficult than a used housing as the teflon is permanently deformed. As long as there’s no debris in your cooling system, this should last the life of the engine.

[George Hill]

It appears to be a carbon impregnated PTFE (Teflon) wiper seal. I wouldn’t expect much if any wear, although ... As long as there’s no debris in your cooling system, this should last the life of the engine.

The thermostat doesn't move against the seal except for when it is installed so I wouldn't think it would wear at all? My biggest concern is that it would loose its tension against the thermostat housing. I don't know if that is a realistic concern but I have seen the seal fall out (and it was not reinstalled whether on purpose or accident and boy did that create a huge headache to figure out). I've also seen (2) cars have coolant temp plausibility faults until the seal/housing was replaced.

...I did replace my tstat housing at 180k miles to rule this out as a failure mode. Pressing a thermostat into a new housing should feel noticeably more difficult than a used housing as the teflon is permanently deformed...

I along with you generally prescribe to replacing parts as a preventative rather than because it has failed.

[Bry5on]

The thermostat drags against this seal as it opens in the s54, it’s an interesting design. When you remove an old thermostat, you should see witness marks from where the seal rides. Interesting that most thermostats I’ve seen now didn’t open completely straight, based on the witness marks.

If one fell out, that would be a time to replace with a new one! Good call there, that would be hard to debug.

[George Hill]

The thermostat drags against this seal as it opens in the s54, it’s an interesting design. When you remove an old thermostat, you should see witness marks from where the seal rides.

You are absolutely correct, bad memory on my part, thanks for correcting me.