MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Dorman emergency welch (core) plug failure

First a bit of background. Over the years I have seen a few core plug failures at the race track when the engines are working hard. Most are due either to faulty installation initially or as a result of an issue elsewhere in the cooling system. So to avoid such disappointment, a couple of years ago I ordered (5) of the Dorman plugs mentioned on Barney's site as spares.
http://www.mgaguru.com/mgtech/cooling/cool_105a.htm
Good old Amazon - I ordered (5) and got (5) boxes of (5) but they only charged me for (5)! So now all my mates had spares.
About a year ago a friend popped one at race meeting and fitted one of the Dorman plugs - it is still in place and hasn't given any trouble.
Last weekend at Phillip Island raceway another friend popped a welch plug - while this engine has been trouble free for several years this is the second time in the last year it has blown a welch plug so he thought he would use one of the Dorman plugs - it failed to seal, so he tried another and another and another. All failed to seal. Has anyone else had this problem - (these were marked Made in China on the boxes so maybe poor quality reproductions). I must admit trying to fit in the pits is not like in a workshop. It wasn't a case of not tightening the nut enough, on a couple it deformed the hex stamping on the outer section significantly and acorn nut became thread bound.
One issue I noted was the face that goes in to the core hole was wavy but this shouldn't effect it as it doesn't seal on this surface.
All leaked when the engine was brought up to operating temp.
(Engine is coming out next week as looks like head is cracked). Has anyone else had problems with these plugs?
Mike




Mike Ellsmore

I've been running these plugs for 20 years in various engines. The genuine Dorman plugs are stronger than the aftermarket ones I've tried, especially the stud itself. There have been a couple times when I couldn't get a good seal and had to put a bit of green locktite in the hole first, but other than that I've never had one fail.

One positive aspect of these plugs is that if they do begin to leak, you can easily tighten them up and stop it. The hardest part of installation is keeping the plug from rotating as you tighten the nut. Once it beings to snug, you can let go of the base and just tighten the nut itself. No need to go tighter than necessary for making a seal, since by doing so you're only pulling the inner cup farther out of the hole.
Steve Simmons

Dorman is not a manufacturing company with their own facilities, they are an engineering firm that outsources all of its manufacturing throughout the world. It appears that about 75% of their products are made in China, so "Made in China" may not necessarily denote a knock-off. They generally have a good reputation for quality parts which exceed OEM requirements. I'd reach out to them as they seem to maintain a good "ear" for what consumers think of their products and it seems they want to know if something fails; here's a link:

https://www.dormanproducts.com/pages/forms/support.aspx

Nick Kopernik

The ones sold by Dorman do have their name stamped on the exterior. There are also knock-offs that have no markings or simply "China". The difference in quality is noticeable. That said, even the older Dorman plugs were slightly better than their current offerings. The older ones were a bit thicker and stronger all around, the color was a bit darker and the stamping was deeper and more pronounced.
Steve Simmons

The ones I received do not have any stampings on them. Go back to Dorman falls in to the too hard basket for us in Oz as they needed to be imported as no readily available here.
Mike
Mike Ellsmore

This thread was discussed between 24/09/2018 and 25/09/2018

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.