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 TD TF 1500 - Core/welch plug replacement

I think I have read most of the previous threads on this but on the TF it is more problematic with its pressurised system.

I recently had a blown core plug. The large one under the exhaust manifold. I replaced it with a good copper one that seemed the right size (circa 48mm; 1/78") and fitted snugly. I used some Stag jointing paste after cleaning the aperture carefully and smoothing any rough areas. I used a short heavy hammer and a socket to expand the copper plug with some solid wacks. The motor is in situ. All seemed good but the leak is there again and everything has to come off!

I can do it all again and this time remove the side panel as well and seek access that way.

Are expandable plugs an option? I can see them with the same dimensions.
M Hyde

Hello, how did you set the plug with the hammer and socket? Welch plugs are usually banged to the center with a ball peen hammer. Something similar in shape/hardness struck in the center of the plug depresses and thus expands the plug. A single blow is best.

I apologize if this is information with which you are familiar.

Regards, Tom
tm peterson

Expandable plugs are really only a temporary fix. A lot of folks here in the US use an epoxy two part adhesive, such as JB weld on the edge of the plug.


I am not familiar with Stag Jointing paste, but it says it is a welch plug sealant.

I use a flat round aluminum dowl that is about 3/4 the size of the disk to flatten the center.

Bruce Cunha

Thanks Bruce and Tom. I set the last one in with a socket that was about 1/2 the diameter of the welch plug and a heavy short hammer - from side on as necessary on the TF. I could remove the side panel and try it that way I guess. On the Dorman-type plugs there seem to be two versions. One type looks more permanent?






M Hyde

Installation - I have a nice short, heat flat hammer that I used on a socket at the centre of the 'plug. Now that I have the leaking one out, I can see it wasn't in as far at the top as it was at the bottom. I was trying to confine my blows to the centre and not work the edges.

What technique did/do you use to get them in, centred and expanded? There are many versions. (:P) I could drill a hole in the side panel above the removable panel I guess and fill it later ....
M Hyde

I have purchased and used various pry bars at times. Ones with various curves, cut off a portion and rounded the end to a radius to be able to “reach in” to set Welch plugs in hard to access areas.
I have a TD and am not familiar with sheet metal of a TF , but on other cars cutting near the 90 bend left me with a short stub in one direction that I used as the setting end with the rest of the bar used as a handle to position the new “tool”.

The plugs are soft enough that if you need to “dive” the plug into place, you risk deforming the rim of the plug preventing it from sealing. If you clean up the hole thoroughly the proper sized plug should press in place.

I would retire the socket as a setting tool.

Regards, Tom
tm peterson

I am afraid the only way on a TF is with a clear strike.
The problem is both the wing and side panel have to come off. I know it is a PIA but the only way, it is time consuming but not as much as taking the manifold out half a dozen times..
Even if a previous owner has cut the side at the wing/panel bolt line the wing still gets in the way.
Also, did you mean brass core plug, copper would deform without wedging into the seat.
Ray TF 2884
Ray Lee

I think you have it right Ray. I have taken the carbs and manifolds off twice now and I don't want to again! Yes "Brass'.

Merv
M Hyde

Merv - I am away traveling, and did not see your post. I make and sell brass core plugs, to replace the original steel ones that will rust and leak, without warning. Said without modesty, mine are considered the best available.

A huge mistake people make is trying to fit a 1-7/8 welch plug in a hole designed for a 48MM plug.  The usual dealer sells a set with incorrectly-sized plugs, that will pop out fairly soon after installation - I get requests every month for the correct ones, to replace those that don't fit - mine DO fit properly.  Commercial plugs in brass (not copper) are not available, except from me - I have been selling them world-wide for almost 15 years, with great success.

Temporary plugs are just that - there is no brass Dorman expandible plug to fit, and the rubber plug may or may not last - it is in a very warm place on the engine.  On a TF, of course, installation is most difficult, due to limited access.  The IDEAL is removing the side cover and wing, which is a LOT of work.  Without this, there is simply not enough room to swing a hammer to dimple the core plugs, a job best done with the engine removed.  

My best suggestion is that you remove the manifolds and carbs, to access that area the best you can.  Then obtain what is called a "Palm Nailer", and put a small rounded anvil into the hammer end, using it to dimple the center of the core plug.  Surprisingly, it works a treat, and saves removing the side panel and wing.  I will be home the middle of next week, and can easily send out a set of proper core plugs.  Let me know, and see mgtrepair.net

Let me know if I can help.

Tom Lange
MGT Repair
t lange

I should have said that with a helper it is not a difficult job.
Leave the wing fastened to the side panel and take them off as a unit.
Ray
Ray Lee

I must say, I use Tom’s core plugs exclusively. I can attest to the failures of steel and the brass plugs sold by the usual US venders. I would in all honesty suggest you replace not one but all water jacketed steel plugs while you have access. I believe the palm nailer that Tom is referring to is commonly used for roving ships nails on wooden boats. I have seen them in use on several YouTube videos. (ShipHappens comes to mind as a reference ). ). Not sure who supplies them. I have also used a hand held pneumatic panel cutter with a hammer head shank but found it difficult to control. But that was on an XPAG in situ in my TD. You may still have space limitations if the wing isn’t removed on your TF.

At any rate , if you currently have steel core plugs installed it is imperative that remove all of them for replacement. If one has failed surely the rest are not far behind. Note that there is a hidden core plug behind the flywheel as well and the engine must come out to replace it unless you pull the trans, oil pan clutch and flywheel in situ to gain access. The plus side to this endeavor sis you can check you bearings and seal up any oil leaks while your at it. Not a pleasant job, but then nothing is when it come to working a TF as you well know. Although nowadays TFs are considered beautiful cars and are coveted by many, MGs engineering has a lot to be desired when it comes to engine bay access.

Bill Chasser
W A Chasser

See my comment on the MG EXP web site for using a Dorman rubber expanding plug as a forever repair/ replacement
More than 23 years/ 60,000 miles with no worries but only in this position
Len
Len Fanelli

Thank you gentlemen for the excellent advice. Also sorry for the double posting, but anxiety creates action.

I can get plenty at 1 7/8", but they ain't 48mm. Conversion among inch fractions, inch decimals and metric is a constant hassle. We changed to metric in 1974 and it has been a godsend, particularly for detailed, fine measurement and our understanding and comparison of precise items.

I had a message from Tom L last night with his usual good advice on the size as well. Some of the ones I can get here are I believe 48mm, but I need to confirm that. That may be a significant part of my issue. Bill also mentions this and the limited capacity to get a square strike on the 'plug in the TF engine space.

Tom also suggested with the congested space in the TF, that the small device below works well in the confined space, with a suitable adapter on the 'hammer' end. (https://www.totaltools.com.au/82124-milwaukee-m12-palm-nailer-bare-c12pn0). I still may need to remove the front wing and side panel, however. I can't see that drilling a hole through the side panel would fully line up square with the core plug. Maybe I am wrong on that, however. Good suggestion on that aspect Ray.

Tom is travelling now so I will need to see if I can get some 'proper' 48mm brass dome core plugs here first. I can't get any of Tom's for some time it seems.

Len, sealants seem to be a mix of science and folk lore to some extent but the modern ones seem to offer more flexibility and specificity. The Permatex Core Plug Sealant seems good as does their 81724 Ultra Blue. I used some JB Weld last time on the outside, mainly to prevent complete fall out on the road if it ever leaked again. That aspect worked but JB is not a sealant and is a pain to remove. The aperture is now clean and as smooth as I can get it (image).

Last, I will get a suitable Dorman plug to fit the inner aperture (I need to measure the inner dimensions of the stepped hole) as a back up when travelling.






M Hyde

Premier Welch Plugs -- BD48MM

If the hole's a bit 2nd hand--Loctite press fit repair- just wipe a bit round where the plug fits and wack him in as normal
you can get the loctite in a tiny little tube that'll be enough for a lifetime of welch plug repairs--takes a couple of hours to dry out properly

willy
William Revit

Gioid advice Willy. Locktite 660 I believe. I have ordered some now.
M Hyde

Just had a look on Heritage MG's website and they're listing a full set of brass plugs for about $35, they might stock the 48mm seperate----??
William Revit

Just adding this drawing from an engineering shop to the debate - I am intending to make two sizes of this tool to install XPAG Welsh Plugs. Just need to measure up and size the tools......the task list continues to outstrip the hours in a day.....

Safety Fast

Tony
The Classic Workshop


A L SLATTERY

or if you know someone with a lathe an 1 15/16" or 2" one would spin down to 48mm size easy enough

Good looking tool Tony
Don't know how many plugs i've seen fall out with just a little dimple in them-and don't know how many writeups say to fit them like thay-I like to really whack them down to 'almost' flat to get the maximum expansion out of them---If you were to make up that tool i'd be tempted to have a slight concave finish to the end of it, only very slight, but concave ---I like the look of that-
William Revit

Here is a picture of the aluminum dowl I use. it does have a slight concave end.

I used the Permatex 660 core plug sealant on this engine.





Bruce Cunha

I have some of the 660 Permatex thanks Len. Looks most suitable. Really like Tony's drawing and the slightly concave suggestions. I have a few old, heavy Hazet drifts and this one is 17.5mm diameter at the end. The end is flat. Could it be made slightly concave? Is that what you are suggesting?


M Hyde

If it's only that 17-18mm size i'd leave that flat and just work around the larger plug til it's 'almost' flat
The concave end would be best suited to a drift about the same size as the plug just to keep a bit of shape in the finished wacking of the plug
William Revit

I would need a drift about 40mm to do that then? That is big. By 'work around' Willy do you mean from the centre and a bit out?
M Hyde

I do also have some nice solid 26mm billet bar.
M Hyde

the plug won't care if it's 17mm or 20 just use what you've got--i tend to give them a bit of a hit in the middle first to get them settled into place and stuck and then go probably about 1/3 of the way accross the plug and then work round in a circle at that till they're almost flattened out but not quite flat
William Revit

On my TD we had to lower the wing to get access to the badly installed plug. I replaced it with one of Tom's. We used a 1 inch steel "drift" long enough to allow safe whamming. One good wham was sufficient.

Jud


J K Chapin

"Now that's a hammer". I seem to have three options for installing the new brass plugs when they arrive.

1. Remove the front bumper, wing panel and the side panel, etc., and use as large a drift as possible (around 40-46mm) with a couple of good whacks square to the centre.

2. Drill a hole in the side panel above the vent panel and insert a long thick drift (as above) through there for the job.

3. Tom's suggestion of the hand hammer/nailer. I have tried the one I have on a couple of used core plugs (that I re-domed) and with a short bolt head (held magnetically in the tool). It produces very good thrust power and can be held steady in the centre. It does have a fast repeat stroke/beating function and only allows a smaller face for the striking 'anvil' however.

Of the three 1.0 is a lot of work, 2.0 would leave a large hole to be filled, and even if I used a laser to ensure it could be level and straight with the core plug, is less desirable.

3.0 is an unknown approach to me, but some have done the same successful with an air hammer.

Any further suggestions please??





M Hyde

To be honest- I think you might be overthinking it
It's not a hard job, there are plenty worse places than that that i've had to replace plugs in-
A nice short punch and a heavy hammer is the go for tight spots
If you've got yourself an old 1/2" drive socket set with the usual sliding T handle, they're really good, slide him down to one end and use the bar as a handle, use the back of the slidey bit to hold against the plug and wack the 1/2" bit with the side of a decent hammer
I wouldn't use quite as large a hammer as Judd and his offsider though, it is a thin cast part of the engine block right in the middle there
willy
William Revit

You're right I am over thinking it Willy. I want to get it right this time. I thought it was fine last time actually. I also spoke to the previous owner and he explained that it had popped out about 18 months ago and he had it replaced. When it blew again for me I found that his 'mechanic' had used Araldite to seal it in. It was nowhere near flat. I used the Stag paste I have used in the past and with my short hammer and suitable socket ... well, it leaked again. Too many less substantial blows with a drift that was too small in diameter perhaps.

I decided to remove the wing and side panel and now they are off. It wasn't that difficult really. Now when the new core plugs and Loctite 660 arrive in the next couple of days (two 48mm brass plugs of Tom Lange's and a couple from Sports Parts, for comparison), I can refit it with a direct angle of attack and the right tool. I have a drift of about 40mm with slight concaving on the centre. I also have a flat one of the same dimensions.

M Hyde

All good--just make sure the plug has seated right back in the hole before you wack it, sometimes they can be a bit tight and may need a tiny,tiny little tap on the outside edge to get them seated---If it's not right back and square in the hole it'll expand when you wack it and stay crooked in the hole------------and leak
William Revit

I'm pretty much sure that is what happened last time Willy. When I removed the plug, I could see it was less in on one 'corner'. I was trying not to hit the edges at that time and only work the centre. I will ensure it sits evenly in the edges this time. Are you a fan of JB Weld on the outside, as a way to ensure it goes not fall out, even if leaking in the future? Is there a way to pressure test the new plug by application of some gentle pressure on the rad cap or hose, before warm up?
M Hyde

not a fan of anything on the outside---if the plug's fitted up properly it'll be fine, If you just wipe a bit of the loctite around in the hole as mentioned earlier it'll never come out
You can pressure test with a cooling system pump but don't go any higher than the blowoff pressure of your cap---should be 4lb for a TF
William Revit

Great Willy. I have a Motive Power bleeder pump and I believe I can make an adapter to fit the radiator opening. I only want about 5 psi (my current cap is 4psi).
M Hyde

No need to make an adapter for the radiator cap mounted pressure tester!
Just add an O ring to the flange for the cap and with a full coolant system attach the pressure tester to the overflow pipe
Cheers
Len
Len Fanelli

Great suggestion Len. I really appreciate your help here. Merv
M Hyde

I received one of Tom' Lange's plugs from a colleague in Australia and also 2 brass ones from my preferred supplier here. I have 2 more of Tom's being shipped now.

I measured Tom's against the other "48mm" ones I had received. The others were around 48.25mm in diameter and Tom's was around 48.10mm. Both types fit in the block hole but Tom's fitted in more readily.

Equally importantly, Tom's were 2.11mm thick brass while the others were only 1.6-1.7mm thick. Probably both would fit in with suitable use of hammer and drift/s, but Tom's seemed the best bet. Now I will wait 24 hrs (Loctite 660) and fill the coolant system and then add a little mild pressure via the radiator filler - and hopefully no leaks!
M Hyde

24 hrs curing on the Loktite and then filled the coolant system and added about 3-4 psi pressure via a modified radiator cap for the purpose.

No leaks!

I will reassemble the exhaust, intake and carby components and try a heat cycle tomorrow (before I put the side panel and wing back on).

Fingers crossed.
M Hyde

All good. No coolant leaks but a time consuming job re-fitting the side panel and wing. Appreciation for Tom Lange's better, thicker brass expansion/core plugs. The Loktite 660 jointing compound is an excellent product.

The carbs are running very sweetly now - steady, smooth idle and pulls well through the range. Thanks to Willy and Len particularly. I popped in the slightly leaner GL needles, on Tony S's advice to compensate a bit for modern fuels.
M Hyde

Yay -well done you-
Hmmm--to compensate for modern fuels--
What fuel are you using Merv, normally you need to go a tiddle richer for e fuels----It'll pay you to keep a keen eye on plug colours, especially check after a long hard uphill run. I think you might be going the wrong way----don't go off tailpipe colour, that doesn't tell the story like it used to years ago
I'd be interested to see what result you get with TonyS's exhaust analyzer out on the road--my guess is it's too lean on GL needles

Random question -are you running a std baffle type muffler or a modern/sportier glass packed straight through type

and what fuel are you using

willy
William Revit

Thanks Willy. I use 98 octane with no ethanol. Occasionally 95. I still have the standard needles as well. I will try a longer drive this afternoon with some hills and check the plugs. I also have a ColourTune. I am not sure about the muffler as I inherited the POs new stainless system on the car. I suspect unbaffled.
M Hyde

I did a 10 km drive with mostly rpm in the 3.5 to 4.0 range. Motor ran at about 80 degrees. No dramas. Pulled the plugs and the rear pair are rather sooty and fronts nice and tanish. I used my ColourTune to check 1 and 2 they are in the blue range at 1000 rpm and the rear pair are more yellow (rich) until about 2000, after which they are in the blue range. Fuel and jet heights and float levels are all good. If I am correct the GL needles are the same as the GJ ones at idle but vary further along the needle?

I have a side issue with the fuel pump not completely stopping after shutdown. A few ticks every now and then. No leaks or flooding.
M Hyde

Are you 100% sure your carburettors are balanced/equal at idle and both pulling on equally with the throttle linkage---what you're describing with your mixture sounds like the front carby is opening earlier than the rear--OR--unequal damper springs,--With the carbs on your car being MGA units and having had the odd part or two fitted to them ,could it be possible that the springs or one of them, are incorrect for your car. MGA's have red (4 1/2oz) springs TF's run blue (2 1/2oz)---If it has a red in the rear and blue in the front it'd do exactly what you describe

Your car should have blue springs --I'd be checking that first up and the throttle linkage equalization

checked the needles and yep both sets of needles are equal up to about half way then the GL's lean off a tiddle in the 2nd half---not a good idea unless it's been proven to be needed by testing
The reason I asked about the exhaust is if the exhaust is more free flowing than std, that alone will lean the mixture a bit so running lean neadles as well puts you in the danger zone
William Revit

Willy, I re-balanced the carbs again after their time off the car using the Synchronometer and they were both drawing air equally. I then reconnected the throttle shaft link and set an idle equally on both, that I could work with. I am pretty sure that they are right.

On the springs - both carbs have black springs? If I measure them at 2 5/8" after compression, they both show the same - 4.5oz. This seems pretty to be on the mark for "red" springs? Putting aside their equal nature, should I have light blue 2.5 Oz springs? They both have a slightly conical shape at the top.

M Hyde

Hmm Haven't come accross black springs and they're not listed but they do measure up as red as you say
and
Yep a TF usually has blue springs and GJ needles

It'd be interesting with it as it is to swap piston/cover assemblies over front and back and see if the plug colour swaps over as well
William Revit

and
https://www.youtube.com/watch?v=IfU47Oqq9wA
William Revit

The carbs now have matching float covers, new floats, levers, dampers, needIe and seats, jets, etc., so they are getting close to TF spec I believe. I did the piston 'drop test' ala, John Twist, when I was setting them up. I didn't swap them over deliberately however. I can try that again Willy.

I will order some 2.5Oz (Light Blue) springs today when I contact Midel. As mentioned, the car starts and runs well - but I should be able to lean off the mixture of the Rear more at idle, and I can't.
M Hyde

EDIT: Willy, I checked a few more things about the pistons and suction chambers. Both fall using John Twist's 'drop test' at about the same rate (no springs) at 4-5 seconds. However, I did find that when fully inserted into the chamber, the piston on the rear was left a 1 cm section of the piston sticking out. The front was 6mm. I cleaned out some crud from the damper tube and replaced the damper washer. Now both pistons when fully depressed into the chamber leave 6mm out at the base!

I will order some 2.5 Oz., springs also.

M Hyde

I may have missed it in the postings, but do you have aluminum or brass pistons?
Regards, Tom
tm peterson

Aluminium Tom.
M Hyde

Trying to think out of the box
Aluminium pistons---are they both the same--weight
Early pre-spring pistons were heavier and had a steel ring insert around in the outer edge---it'd be really strange to have an odd pair but it's been done in the past by unsuspecting suspects
might just pay to check when you're fitting your new springs
William Revit

They are matching numbered ones Willy. And have the same measurements. I also fitted a fuel pressure regulator set to max at 3 psi just in case. Those new springs should come today but I am going to Cape York tomorrow for some fishing.
M Hyde

Somehow this thread changed from core plugs to carbs? Comment and observation: Way up in this thread there is a great close of of a well cleaned core plug opening in the block. Look at how rough and uneven the metal is. This is likely due to many years of corrosion. Besides substandard replacement plugs, this can explain some of the trouble we have with leaking and failing plugs today. This didn't happen back in the day that I recall, when the blocks were 30-40 years younger. Just an observation. George
George Butz III

Noticed that as well George, there were some deepish marks there---part of the reason that i recommended the loctite 660 to fit the new plug
willy
William Revit

The recommended loktite was great for that purpose. The carbs stuff apologies. Will move that back to the other post.
M Hyde

I must disagree - the hole in the photo appears rough and corroded, but not around the periphery of the opening, where the welch plug seals. The corrosion is inside the block, where water flows. The only time I see corrosion around the sealing surface is when there has been a long-leaking steel plug, and rust has worked its magic on the block. In that case I use a tiny bit of J-B Weld to build up and restore the corroded area.

One of the benefits of a brass core plug over a steel one is that the brass is softer, and is more likely to fill in small unevennesses.

I have drilled and mounted welch plugs with bolts as handles, guides to be sure the plugs fully seat in the holes - often there is a small bit of rust that stops a plug from seating fully. If the plug is not seated fully, it will probably not seal perfectly.

I will say again that I do not use silicone sealant, J-B Weld, Araldite, or Lock-Tite, and have never had a leaking welch plug leave my shop - or come back. Properly-sized welch plugs, preparation and installation are the keys.

Tom Lange
MGT Repair
t lange

This thread was discussed between 29/04/2023 and 12/05/2023

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.