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MG MGA - Core Plugs

Good morning Gents, again I need your help!!!
One of my engine core plugs fell out of MGA engine last Sunday. The one behind the engine bloc just above of the gear box, not very accessible without removing the engine!!!
A friend informed me that there is a replacement system that is called “Rubber Freeze Plugs”. It is composed of two metal washers, a rubber silent bloc and a long bolt. (See attached picture)
Is this a reliable system, and where is it obtainable?
I live in Brussels, Belgium and no vehicle accessory dealership seems to have any knowledge about this type of system!!
Again thanks for all your support and assistance.
Mike.


Mike PAIN

do a web search on emergency core plug and you will find exactly what you describe

also look for this type
https://mgaguru.com/mgtech/cooling/cool_105a.htm
Dominic Clancy

May only be a temporary fix. I would fit an original replacement, using a stout lever off the firewall to push it in, with a little application of sealant -- not an easy task but worthwhile giving it a try. I would also use copper alloy plug.
Barry.
Barry Gannon

Barry,
I am not convinced by your suggested method.
An original core plug pushes in easily and would also come out just as easily.
Only when the core plug is very firmly struck in the centre with a punch does the diameter increase to hold it correctly.

Mick
M F Anderson

Mike,

Talking to my local MG specialist in the past about this problem, he recons he can get a 'windy hammer' in the space to compress an original core plug. Quick tip, soak in oil for 24/48 hours so it wont rot from the inside out.
Best

Alan
AR Terry

When you put a new original-style plug back in, use red locktite on the perimeter. You can by it in paste form so it won’t run off of the vertical surface.

Jim
JL Cheatham

My personal preference for this is to take the engine out. Not a major job if you are used to it. My inquisitive brain always tends to look one step deeper into why did it pop? Overheating, high pressure etc. I have never had one blow out, but last time I took the engine out I took out all the plugs and gave all the channels ways a thorough clean. I was surprised at the crud build up.

Steve
Steve Gyles


I am presently feeling sorry for myself, having R & R, ed the engine from my Coupe, to fit a replacement welsh plug for the plug in the rear of the cylinder block. It came out while out enjoying an MG Club drive ! !
The new part has cost just $3.50 but its a large task to put it right.
Removing the engine, so that a suitable wire brush attached to an electric drill can reach into the machining in the block, to clean it off properly, is the only way to go.
Its going back to gether, with the suggested piece of flat steel behind--with a bolt thread -so the bolt will push onto the dent in the centre of the plug.It will never be troublesome, again.
The other 3 side mounted plugs look fine.I wonder why this one popped?
Its strange that I have experienced this problem at the time when it was topical on this cite.
The little cars are just great fun. It will be running again, very quickly.
I.W. Cowen.

It's a false economy replacing one, as if one fails, the others will be close behind.

I reckon if you used a very stout plate above the gearbox you could use the Betson Bolt approach without a high backplate. But it needs to be able to give you space to clear the lip on the heater shelf and brace on the goalpost.

I too would take the engine out as the shortest and easiest fix and do it right.
Dominic Clancy

I was at Peter Burgess's having my engine set up on his dyno last week and they were talking about core plugs (probably about a similar thread on the other forum).

IIRC (which I may not have), Peter basically said that on race engines he has seen core plugs pop out because of severe pre-ignition but also because of the water pump causing severe water cavitation at high revs.

I believe he straps the core plugs down on his engines too.

Colyn
Colyn Firth

Chance or witchcraft. I had that same problem this past Sunday. Fortunately, I detected it just in time and stopped the car. I'm going to try to put the cap on this afternoon. I will tell you how I did it when I finished, but without removing the engine.
Gabriel Martínez

It could have been quick and relatively comfortable. My plan is to access from inside the car by making a hole right in front of the core plug and it will continue to be my plan. I made a tool with a 40 mm washer and an 80 mm screw to mark the access point in front of the plug and, surprise! It matches a screw that holds the gearbox cover, so it seemed even easier, but the damn screw must be blocked by rust because it does not move. When I get it removed I will put a metal bar with a socket on its end and I will give the happy plug its well-deserved blow.
Gabriel Martínez

The screw and nut.

Gabriel Martínez

Gabriel

I took that whole cover away and it was still touch and go to get the core plug into place. Its a nut welded to the panel, so all you can do is remove the bolt from inside the car (if you can get to it).

Trying to hit the plug through a 6mm hole is not going to give you a big enough area to spread the core plug. (IIRC that is a 3/8 headed bolt with a 1/4 thread). There is also a lot in the way under the dashboard to hinder a clean stroke on the bar.
Dominic Clancy

Can't believe you have trouble fitting that rear plug, it's the easiest of the set to do
in place, a piece of timber wrapped in a rag over the front of the firewall to protect it and lever off that onto the centre of the plug using a flat washer about 1 1/2"od to prevent the plug being damaged by sharper shaped dents in the centre--just get it all loaded up and give the bar a helping whack and the plug flattens out great
I use loctite flange sealant around in the hole, nothing on the plug, the sealant squeezes up as you push the plug into place, if it's on the plug itself it just gets wiped off on the way in

willy
William Revit

Fact. As the screw was definitely blocked by the oxide, I drilled it to 8 mm. I have tried to keep it with all possible techniques but it has been impossible. Then I stuck a socket to the new plug with hot melt silicone to keep it in the center, I put a joint sealer in the hole of the plug and I put it in place, I inserted the bar through the hole, I connected to the socket and ready, three hits and done. Then I put a screw, nuts and washers of 8 mm stainless to fix the cover and close the hole.

Gabriel Martínez

Another photo

Gabriel Martínez

And from vehicle inside.

Gabriel Martínez

Well Mike, You have started this topic and you have a solution and also the tour of France you have at home, congratulations!
Gabriel Martínez

Watched the start of the Tour on telly last night - looks fantastic around there-

Congrats Gabriel,nice job, there's always a way to fix things

willy
William Revit

Woawwww, First thanks to all you nice Gents for all your comments, tricks and ways to fix this problem. I did insert a shock absorber silent bloc with two washers and a bolt all the way through, and tightened it with Loctite (on the bolt only, see picture) and it looks like it does the trick. But during the winter period I will probably take out the engine and replace all the plugs. Again thanks to all of you, I will certainly let you all know how things turn out later. Cheers.........

Mike PAIN

I would not leave that for long as it may corrode quite quickly. Being steel in a cast iron head it could/would become the sacrificial metal?
Barry.
Barry Gannon

Congrats - It's a boy
William Revit

My 1959 MGA popped a freeze plug back in 1971. I replaced it with the rubber style you picture. I am still running the car with that plug. The advantage of using the rubber plug in my opinion has been that you can be assured that style is fitting evenly all round whilst some mechanics have attempted to install the original metal ones and do not strike it dead center causing a pop-out later on.
Eddie
EWH Haynes

I need a little advice. Core plug in my 57 MGA must have blown out going up a steep hill. Antifreeze and subsequent mix just pours out of the hole, pics attached. Seems to have blown the plug apart. Any suggestions on how to remove the remnants? If I replace the plug should all be ok? Thank you
JJO John

pics, sorry new to the site

JJO John

Hi JJ and welcome to this site

Bit of a weird looking plug you have there-
It's just rusted out by the look of it, just punch it in a bit in the middle (being so rusty it will collapse easily) and then see if you can hook it out with a big screwdriver or similar weapon like a little pinch bar or whatever fits in there
The whole thing comes out, out to the edge of the red paint line there-the new plug will be 1-5/8" diameter If you can get a brass one ,do that, it will never rust out again
You need to get the hole nice and clean before fitting the new plug so a good scrape around in there with a knife is good
A pic of the hole after would also tell what type of plug is needed, usually it is the dish type but some engines have had the hole machined right through and take a cup type
William Revit

I must have looked at that with one eye shut on the phone but now on the PC, looking again, I can see the whole middle has gone from it,If you get a little pinch bar under the edge of what's left there that outer ring part that's remaining should lever out quite easily, and it's the normal dish type plug you need that has to be expanded (flattened) after it's fitted

willy
William Revit

Thank you willy. I cleaned the ring and discovered remnants of a rubber gasket as well. All cleaned up and picking up new plug this morning. Will send pic after install.
JJO John

This thread was discussed between 26/06/2019 and 04/08/2019

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