MGB Register Forum

As many of you will know two of the thermostat studs pass through the water chamber below. I have finally got my rebuilt engine started today and it's running really well. But coolant is literally spraying out under the nuts of the two RH studs. I have tried using flat washers and plenty of Wellseal, but they still leak when the coolant gets warm and is under pressure. (it's the Wellseal that makes them look brown).

What's the best way to stop this? And do the new studs seem, a bit short to you? The top thread is obviously 5/16 UNF. Is the bottom thread 5/16 UNC - I can't remember. Might see if I can get some a tad longer.

Hello Mike,

On mine, which has the filler on the top of the housing, and the bracket sticking out over the alternator, there is much more thread showing on all three studs when tightened up. Probably more than 1/4".

I had it off recently, and since replacing it there's no leak from the struds, even with the engine running static and hot, without the fan running.

Surely the gasket, or a gasket compound, should prevent this from happening.

Mike, hydraulic thread lock is available, and no doubt there are additional "lock and seal" thread locking compounds. Try a search on the internet.

I've never had this problem so it is unusual.

Ian F

https://www.bearings-online.co.uk/item/ ... -50ml.html

Ian F

There is a long thread running on this in the MGA section. I've had this problem on my B. Coolant gets escapes through the treads of the studs into the head, they are open at the bottom to the coolant. (not blind). As has been discussed, if you can get the studs out you can seal the threads with gunge. Be prepared for the stud snapping or the tread stripping. I opted to seal it at the top, replaced the spring washers with plain and the nuts with nylocks. Plenty of gunge and I've had no leaks since. There is a risk of corrosion but the inhibitors in your anti-freeze should prevent this.

A long thread about a short thread........

Ian F

So thread very carefully

Update: The leak is fixed. I used a 2-pronged attack, fitting stainless studs (which are quite a bit longer than the ones I had) and sealed the threads with Loctite 577. I also flattened the surface of the cover with grinding paste on a flat glass plate. I wasn't really warped but corrosion had caused many pits in the surface. It took quite a lot of grinding (and arm ache) before I had a flat surface all the way round. I didn't remove all the pits but it was obviously enough as there are no leaks even when up to temp and pressure. Thanks for the suggestions.

Very good! Thanks for the feedback,

Ian F