Better Fix for Thermostat Housing Leaks?

[Aleman]

The thermostat housing is made of aluminum which bends and gouges easily. It can get damaged, and that commonly results in coolant leaks.

Most people say to put a bead of RTV on the surface of the housing cover where it contacts the base, then button it up at the proper torque spec. This works for a while, but it's messy to clean up when you have to open it up again to change the thermostat down the road.

Has anyone had success cutting a paper gasket for the therm housing? I would expect that to be a better solution.

If that works, then I wonder why the hell BMW didn't take that approach from the get go?

Thanks!

[digger]

which part leaks? there is an o-ring there, pretty sure it is the part that seals. you can buy new parts they arent very expensive for what it is

[Aleman]

Better Fix for Thermostat Housing Leaks?

which part leaks? there is an o-ring there, pretty sure it is the part that seals. you can buy new parts they arent very expensive for what it is

I have a new o-ring, but the housing is leaking like a sieve. I think when I was scraping off the PO's RTV I scarred the housing cover-to-base surface. If the rubber o-ring really is the only seal that's needed, I'll take a closer look at the lip where it sits inside the base. Maybe some debris fell in there.

....or I'll go and cut me a paper gasket LOL


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[digger]

paper gaskets can work but id use some aviation cement non hardening type and have metal on metal. give the faces a quick linish first off

[e30davie]

Its just an o-ring that seals according to the schematics

http://bmwfans.info/parts-catalog/E30-2-doors/Japan/325e-M20/L-A/oct1986/browse/engine/cooling_system_thermostat_housing

Both surfaces where the o-ring sits need to be perfectly clean.

Unless you are talking about part #4 in that link, which is the gasket from the thermostat housing to the head.

[jeffnhiscars]

I spent a lot of time on this leak until I realized I had crimped the o ring so it wasn't seated properly. $2 later it's been fine.

[TobyB]

Paper gaskets don't work so well on coolant- it wicks its way down the
paper, eventually softening to mush. Meanwhile, the aluminum starts to corrode.

Nissan did it that way a long while back. It sucked getting old parts engines apart...

t

[digger]

the one on the back of the head and to the head is made of cardboard type stuff, buy a sheet of stuff from ebay and make your own. personally id be chasing the root cause and fixing that

[cscracker]

Yeah, the O-ring does all the sealing, no paper gasket or RTV necessary. If yours won't seal it must be in pretty bad shape. A new housing isn't too expensive (~$40-50 for both the housing and the cover) and chances are, your leaky one is also super crusty everywhere else.

Housing
11531730470

https://www.ecstuning.com/b-mtc-parts/thermostat-housing/11531730470~mtc/

Cover
11531265059

https://www.ecstuning.com/b-uro-parts/thermostat-housing-cover/11531265059~uro/

Against the block, that side does need a gasket. If you replace the housing, you'll need a new one.
11531722692

https://www.ecstuning.com/b-genuine-bmw-parts/thermostat-housing-gasket/11531722692/

[digger]

id by the genuine stuff for an extra $50 all up, MTC and URO are the worst brands around

[Aleman]

Better Fix for Thermostat Housing Leaks?

On my vert, I just replaced a bad thermostat and put in a new housing gasket. It leaked pretty bad, but I would say that I probably had some old RTV somewhere on the sealing surface. I went and put RTV on the seal and no more leaks.

My other E30 got a new thermostat 5 years ago, and I've put on about 6k miles since then. Coincidentally, that therm housing is now leaking for no reason other than age maybe. I guess I will know more once I open it up. How long should a gasket last? Seems like this could be one of the M20's weak points.

Thanks for all the advice so far guys. Good stuff here


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