MG T-ABC

.... you find that apart from a warped head you also have a leaking core plug.

Back in the day we used red lead, a mixture of lead powder and red hermatite to seal core plugs, what is used now?

(XPAG engine in a TC)

Norman, I used to work for a CAT dealer and when they replaced core plugs they coated the edges with a two part gray epoxy that looked suspiciously like JB Weld. So that is what I use and find no problems.

Considering the system has zero pressure, I find it rare that I have to use any kind of sealer on the plugs. If a block has pits then I may use a tiny smear. Two products I've used with good results are Locktite sleeve retainer (usually only on pressurized systems) and a small smear of Permatex Right Stuff when the surface is rough. I've heard of people using JB Weld to fill pits and then sanding it smooth but it seems like it might be hard to get it perfect. I've also seen people smear JB Weld on top of a fitted plug but this seems totally unnecessary to me, and probably a pain to remove and clean later. I've never tried it personally though, so maybe it isn't as bad as it seems.

Might try some regular blue Hylomar to fill any fine pitting on the block where the plug seats.

With a 70 year old casting I think it does need a sealant. As I said above we used to use red lead, even on newish blocks.

I've ordered some of this: https://enginecoreplugs.com/product/cor ... ml-tube-2/ Problem is it's coming by post so may take week or so to get here. If it does I have Hylomar in stock so I'll use that although it's not meant for sealing core plugs, it's for ali-ali gasketless joints.

If one steel core plug is leaking, others will surely join the chorus, and start to leak without warning. Brass ones are without question the best, and will never leak.

Tom Lange
MGT Repair

JB Weld works just fine for filling pits and building up alloy castings, particularly like the typically corroded thermostat housing on your TC. Why wouldn't you be able to sand it smooth, it's just like any other epoxy? You know that gas tank sender in your petrol tank that always leaks and screws up your nice new paint job? Well JB works just fine as gasket sealer and takes care of that and is impervious to fuel. It has pretty decent heat resistance too. Not difficult to remove as it really isn't a weld. "Bad as it seems", but you've never used it??

Yes, I've used it, just not on core plugs because mine don't leak. But I know others whose plugs do leak and have used all sorts of products with mixed results. I use Right Stuff on all other areas of the cooling system - thermostat, elbow, rear plate, etc and it works marvelously, on both pressurized and non-pressurized systems. In fact I use it on just about anything I need to seal on an engine. Best general sealer I've used!

Is Right Stuff available in the UK? Google doesn`t indicate it is unless under another name. Who are the manufacturers please?

Permatex makes it. The black stuff is what I use. It comes in 1-minute and 90-minute versions. The aerosol can is really useful and makes it super easy to apply just the right bead. It also doesn't dry out in storage, although the nozzle can get plugged after a while so you have to clear that before using again.

See here: https://www.permatex.com/product-catego ... et-makers/

This core plug is probably leaking due to me not realising teh head gasket was leaking and driving the car with no water in it. The block got very hot. The other two look good but I do have new ones in case they start to leak.