What sealant for a Thermostat Housing?

[HustleRussell]

On the 525i, I've replaced the thermostat and housing. It's a plastic composite housing with a rubber 'O'-ring. Although the housing was correctly torqued, I'm finding that the engine is losing about 300ml every 500 miles from the join between the composite housing and the cylinder head.
What sealant is suitable for this? I have clear gasket sealant (strong enough?) and nasty black Terostat stuff which I'd probably never be able to get off again!

[Snake the Sniper]

You sure it's not over torqued, or been over done in the past, and slightly distorted the housing? Might be worth checking the housing sits flat on a known flat surface. If you can't be bothered though, just about any semi-setting sealant should do it. Just a smear in the housing, fit the O ring, and then another smear on the mounting surface.

[HustleRussell]

I used a new housing, albeit a cheap non-OEM one. Maybe a BMW housing would've been better. It looks like this anyway;



The housing I removed had been re-used with sealant so I wonder if I have slight porosity in the head or something.

Sounds like the clear sealant will do it anyway, I use it on my diffs/gearboxes etc but wasn't sure it'd stand up to 100 centrigrade water at 2 bar pressure...

[Snake the Sniper]

If the sealant you have is ok on a diff, it'll be fine there. Diff's get incredibly hot.

[ch427]

clear sealant will be fine but it sounds as if the non oem part isnt quite machined right