[1.6 FSI] - Thermostat Housing Issue O-ring

The opposite side is entirely flush aside from some corrosion (admittedly, maybe severe pitting in my case) but well inside the o-ring internal perimeter.

Mahle is the OEM supplier for this one I can confirm.

Andy, is there any chance for you to check the new housing for flatness with a straight edge maybe?

Evros
Good Afternoon Evros,

Sorry I missed this.

Just checked with old steel rule and which ever direction I chose it looks flat.

Andy
 
I meant the Audi used part, and the new Mahle. Since they're probably separated by quite a few years in production.
Just curious if the possible change in "O" ring cross section was matched with a change in the radial slot.
Mac.
Good Afternoon Mac,

Sorry for the delay in replying.

I checked with clock face on each housing. The new one is 6/17 (I've had it for two or three years) and the used one is 5/07 (so not original).

The cross-section of each seal looks it would have been the same but as I said above the used one is squashed flat from its working life on what would have been the proud part. Seal dimensions look the same.

Andy
 
Just to put closure to this:

1. I have lapped the housing on a piece of sandpaper taped on a steel bench (tested against a straight edge).
2. I used white board marker and the help of a fine file (large one) to take off some material.
3. Repeat 1 and 2 many-many times.
4. Tested in a dark room with the face being pressed against the bench and a flashlight.
5. Stopped the process until the face was flat enough.

I then put it back together using Versachem red RTV good for 350 degrees celcius. The loctite I could find locally was only good for 200 intermittent. At this stage I reused the old o-ring since I have already removed some material and if the housing was going to leak again I'd get a new one.

I put it back on the car after having lapped the cylinder head where it would meet the housing. I replaced the death pipe for a 2nd time in 3 months because it was cheaper to buy as a set rather than getting the o-rings for it separately.

Then the themostat began leaking at which stage I took it out and used a bead of RTV to dress the o-ring. Its o-ring has the same shape as the one on the cylinder head side but larger diameter.

To my surprise it has remained leak-free and kept all the coolant in for a week now.

Lets see how it goes.

Evros
 
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