Welch Plug leaking - LHS

Hello All, the '63 MK2 - normally drum tight - is loosing coolant from a failing plug under the exhaust manifold. Any recommendations as to provider or any sad stories? Regards. Paul.

I know there is 2 types , disc and one with a side on it .
I replaced the disc type before , they are convex when you place them in the block , you have to straighten them out by hitting them , so they fit tight in a slot , I used a cut down branch of a tree , rather then a socket

Anyone use and have success with the rubber ones with a bolt in the middle that you tighten to cause it to swell out and seal? I’m always nervous about pounding anything near the block In case I miss with the hammer.

I have used both the Dorman expandable metal and expandable rubber plugs for in situ replacement of the Welch plugs with some mixed results
the metal (quick copper seal) 1 ¾ still requires a bit of light tapping to fit. Somewhere I read that you weren’t supposed to use any sealant, however installing them dry always resulted in a leak. Someone suggested that we use JB well which to me, seemed drastic. I settled for Permatex form-a-gasket sealant #1

Better success with the Dorman quick seal expansion plug. You need to purchase the 1 ½ inch Size rather than 1 ¾ as the lip of the core hole is insufficient to hold the 1 ¾” plug. Again you need a little tapping to fit the plug in the 1 ½ inch orifice. I have read the plug lasts only a few years perhaps three at the most, however, some American cars use these rubber plugs as original equipment
65 Mk2
Cincinnati OH

Had some in Tweety, and I’d used them on other occasions: worked well.

Hi Gents, thanks for the replies. I replaced a plug recently in my Morgan using this product with success - the PO had the plug in the toolbox - all ready for me to fix! Have not done one on a Jag before. I will see what I can find based on above. Paul.

I recommend using the convex type, but brass, not steel. Easier to flatten out and last forever. If on the exhaust side, you will need to remove at least one manifold, so not much chance of causing any damage.

Thanks. Potential shipwright’s disease problem there as one of my downpipe studs is stripped. Paul.

Had the same issue with my S1 Sov. Remove manifold, cut old stud off flush with manifold face and then drill out stud using progessively larger drills until the old stud will work out. Then clean the thread in the manifold with thread tap. Do it once, do it right and use brass nuts, End of problem. I’ve found over the years that short cuts never pay off if you intend to keep the car.

I have a related problem - frozen nuts (the hexagonal type of course), studs with threads half corroded away, studs brazed in place…

I want to cut them all out and start again and it might include thread inserts. I would prefer st. steel studs with brass nuts and washers. Is there any problem with this mix of cast iron, st. steel, and brass?


No problem. I use brass or manganese bronze nuts as well. The long series are best - more threads, more torque and less chance of stripping. Paul.

Thanks Paul, I was sure this configuration would be effective but it is worth asking if anyone has had any adverse experience.