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 MGB Technical - Core Plugs

I have a leaking core plug (the middle one on the side of the engine block) that I want to replace with the engine ‘in-situ’.

Has anybody done this replacement with the engine in place and have you any suggestions or tricks to allow this to be done. My main concern is ‘hammering’ the new plug into place with the limited room available in the engine bay.

I’m thinking that to make more room to ‘swing’ the hammer I will need to remove the dizz cap, plug leads and the coil, also the oil filler and maybe the oil filter bracket and the oil cooler hose (if it’s in the way). Will this be enough room or will the close proximity of the body prevent enough ‘swing’ on the hammer to allow enough force to be generated to drive in the plug.

All thoughts and/or suggestions welcome.

mgb roadster. 1800cc standard engine with ‘cup’ type core plugs

Thanks Guy’s.

Brian
Brian Davis

Yes, did that one successfully years ago. I can't remember if I removed anything and swing was limited as you say but it did go in, I smeared sealant on first. I have the cup-type rather than the dished type which may make a difference. If you have the dished type you need to use a broad implement across the face rather than a pointed one to get full pressure round the edges.
paulh4

Paul.

They are the cup type and I have a 27mm socket than just smaller than the cup to use as a drift. Hopefully will apply even pressure around the edge.

Brian


Brian Davis

Rather than drive it in with a socket in the centre I would coat the rim with Loctite and use a copper hammer to gently tap the edges of the cup until it is flush with the surface.
Chris at Octarine Services

lol, there's heaps of room for that one,Depending on what model your MGB is, If it has the upright spin on oil filter, that needs to come off then there's heaps of room, just put some rag over the oilfilter base to stop any rubbish landing in that and away you go, and
Yep, hitting on the edge is best , I've got a drift about 2.5" dia and about 3" long that I just hold square against 'em and whack it -using the biggest hammer I can physically fit in there, bang bang rather than tapping away there all day
William Revit

Chris

When driving the core plug into place should it be flush with the surface or slightly recessed into the block. The current ones are about 2mm recessed. Whats the current thoughts on this.

(The engine is one of your rebuilds so you would have installed the current core plugs - Oct 2005 with about 12k on the clock).

Thanks. Brian
Brian Davis

Normally the hole for cup-type has a deeper 'seat' than the dished type, and the plug can be tapped down as far as that. That would give a little more sealing surface than if a gap is left by only tapping it down flush, but tapping lower than that won't be as easy as getting that far.

An original on mine is a couple of mm recessed (left) but the one I replaced in-situ is flush (right) and has been fine. The one that came out had rotted through from the inside, but the others are all still there many years later.



paulh4

Normally there is no internal lip on the hole for cup type plugs, so it is possible to drive them too far.

The method I use is to place a copper hammer on the cup and hit that with a club hammer - the copper hammer acts as a drift with a convenient handle to hold!

Because the face of the hammer is somewhat convex the cup gets driven a little past the surface but whether flush or slightly recessed doesn't matter.
Chris at Octarine Services

Just to add to Chris' top advice , the depth of cup type plugs varies a bit as well depending on the brand---That new one you show in the pic. appears to be a fairly deep one so it wouldn't want to go in very much past flush at all-
If you have a look at Pauls pic. you can see his new centre plug appears to be much shallower than yours--not an issue, just don't drive that deeper one in much or any past flush
It amazes me that you guys over there are still using steel plugs, we've been using brass plugs here for years, it'd be hard to find a steel plug
We also have stainless but I'm a bit warey of them,ok as cup type but with dished it's a bit scarey really, you have to hit them that hard to get them flattened, it just doesn't feel right
Brass is good though
willy
William Revit

If there is no internal lip on the hole in the block what's the best way of getting the existing core plug out. Will knocking a hole in it with a punch drive the plug back into the block?

Brian
Brian Davis

Drill a hole and insert a large self taper. Then use a claw hammer to pull it out!!

Just like that!

Colin
Colin Parkinson

Usually i get a punch and drive the top of it in,in that area you showed where the socket was, up the top though, till it tilts over about 45 deg. then get your multigrips and lever it out
best not to punch on either side of that plug as the bores are fairly close
If it happens to fall in, don't panic, it won't go far, but don't leave it in there ,you can dish it out fairly easily
William Revit

As Willy says, knock the top of the plug in to tilt it and pull it out with pliers / molegrips from the bottom.
Chris at Octarine Services

I used the Dorman plug on my car recently - survived a day on the track at Phillip Island Raceway. I am a believer (so far)!
http://www.mgaguru.com/mgtech/cooling/cool_105a.htm
Mike
Mike Ellsmore

This thread was discussed between 05/06/2020 and 09/06/2020

MG MGB Technical index

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