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MG TD TF 1500 - Core Plug & Head Gasket Leaks

Two years ago I had my engine rebuilt. The machine shop work was excellent. The assembly work was horrible. I had to pull the engine to redo the front seal, the rear seal, the sump gasket etc. etc.

A couple of months ago I noticed quite a few leaks from several core plugs. I called the owner of the engine shop and I was foolish enough to use the product he recommended. It did no good at all.

My own research let me to a group of products under the name of Blue Devil.

The sealant product is a liquid product that you pour in the radiator. Apparently there is a chemical reaction that starts to form a solid product at a point of temperature change. The product sees this change at the leak. It can be left in the system when you are finished.

It does require a bit of time and work to prepare your car for the product. After removing the thermostat I thoroughly flushed the radiator and the engine. When it appeared that the water was completely clear I removed the petcock from the side of the engine and scraped out any sludge remaining. I then follow the instructions for the Blue Devil radiator flush product.

Then it was time to fill the system with water and Blue Devil Head Gasket Sealant. Core plug does not appear in the name of the product but their tech support people were very helpful and adamant that the product would work on the core plugs.

I added a dye to the system to check for leaks with my ultraviolet flashlight. I now have a couple of hours of vigorous driving on the car and do not see a single drop of water from any of the 4 or 5 plugs that were leaking.

I will let you know of any leaks in the future but for now I feel comfortable recommending the product.

https://store.gobdp.com/head-gasket-sealer-directions/

Mort
Mort Resnicoff

Such products use sodium silicate (water glass) as the principal ingredient, which sets into a glass like structure at around 100C. Ok as a temporary fix as long as none can get into the engine oil (then very bad).
Dave H
Dave Hill

I tried this very product to get a few more weeks out of a Subaru with a blown head gasket. It was the fastest way to dispose of fifty bucks. Did not work. If done correctly, there should be no leaks with the XPAG. If you use a good head gasket, and Tom’s brass core plugs, installed after careful cleaning, using a very thin layer of JB Weld and proper installation, there should be no coolant leaks.
It sounds like the product worked for you. Keep us posted with results.
Be well,
David.
D. Sander

If that many core plugs are leaking - no matter whether steel or brass - there is something wrong with your installation process.

When people contact me about a leaking core plug it is almost always that they either did not clean the hole adequately, or else they did not dimple the core plugs enough to seal in the hold. Usually a bit more oomph in dimpling the core plugs seals them just fine.

Tom Lange
MGT Repair
t lange

Leaks shouldn't be a problem in a non-pressurized system. Before pouring in a sealer, I would try hammering the plugs in a bit harder. It's also possible to hammer them in too far where they begin to shrink again.
Steve Simmons

With that many leaking, I would be concerned that one could just fall out. This has happened to a couple people in our area, and you have instant overheating and possible severe engine damage. As much money as a rebuild costs, I would really consider changing them. Fairly easy to do- pull the carbs, manifold and exhaust. The rear one is a different story... George
George Butz III

David S.,
My core plug leaks were too small to be seen. All I could see was the evidence of the leaks. Head gasket leaks can vary from microscopic to substantial. Perhaps your experience was with a larger leak that could not be plugged with this product. It seems to have worked on my leaks. At least, so far, so good.
I did supply the machine shop with Tom's brass plugs. You would think an experience automotive Engine shop could prepare and install them correctly. But taking into consideration the lousy job they did on reassembling I am sure the problem it is due to faulty workmanship. Of course this leaves me with the problem since I would never consider letting them touch the engine again.

Tom L.,
I recall reviewing the installation process with them when I supplied the plugs. I must have talking to a wall.
They did use an epoxy and I can see the evidence of the ring of epoxy around each plug. They either did not clean and prepare the hole properly or they did not dimple deep enough.
It took the leaks one and a half years to show up.
Based on the fact that there maybe crevices in the recess and based on the fact that the epoxy has hardened over the past year and a half do you still think that it would be effective at this stage trying to improve the dimple?

Mort
Mort Resnicoff

I have Toms brass plugs in the TF and not a one has ever leaked. Cleaning the seat in the block is paramount for a good seal, I use a small rotary wire brush for cleaning, I also use a 3/4" socket with a couple sharp blows to set the plug. Works for me!


























PJ Jennings

PJ,
I agree completely. I wish I had done that job myself instead of the machine shop.
Mort
Mort Resnicoff

Even when you do that they can still leak - as mine did. Plenty of experts have had problens with core plugs on these engines. They are old engines, that have probably been rebuilt several times (mine on its 4th rebuid), with not particularly well cast core plug recesses that were shallow to start with and have worn enough to be troublesome. In the end I used lashings of JB Weld to make sure.
Dave H
Dave Hill

The go to substance when installing Welch plugs here is Stag, which is what I went with. Anybody had any problems using this? Cheers
Peter TD 5801
P Hehir

Dave Hill - were your leaking core plugs steel or brass plugs from me? The reason I ask is that the core plugs from the usual supplier are known to be on the small size, and difficult to seat convincingly without leaks - or without falling out. My soft brass core plugs seem to be better at filling slight imperfections in the core plug hole - and they are the correct sizes!

I believe I have seen only two cases when my core plugs could not be re-peened for a tighter fit; in both cases I sent them new plugs and the second installation was successful.

There is still some debate about whether to use a sealant or not. Some recommend using a silicone or gasket compound in the periphery of the hole to fill small imperfections and voids before the core plug is installed. The other school of thought is to use J-B Weld (or Araldite in the UK) around the outside of the core plug to semi-permanently seal it into place. My only concern with that is when the engine is next rebuilt: those sealers are not affected by the usual engine-cleaning solutions, and would have to be carefully chiselled or ground off the block. I would fear for collateral damage.

Mort - I hate to say it but with the reported overall level of workmanship of the machine shop, I would be reluctant to rely on anything they did. I realize it is a big job to remove and replace all the core plugs, but having a core plug leak or fall out can ruin your whole day. The only (unprofessional) test I can recommend is to rap them with a hammer, and see if they ring true, or dully. As with checking a crankshaft in the same way to check for cracks, it is A test, not THE test.

Are there perhaps other repairs to be made at the same time, if you decide to pull the engine to replace all the core plugs?

Tom Lange
MGT Repair
t lange

They were steel, which may well not be as good as brass, but that was all I had at the time. JB Weld can be readily removed using a rotating wire brush in a drill.
Dave H
Dave Hill

Just pulled the core plugs from my 50 TD as part of the restoration. This motor was a replacement for mine that had a catastrophic failure. It was built by an aircraft mechanic in Georgia.

I think I had around 800 miles when the center plug started leaking. Replaced it with an expanding rubber plug. Now I note two additional plugs have been leaking.

I drilled the plugs and used a slide hammer to pull them out. They came out really easy. To easy in my opinion.

I cleaned the edges and will be putting Tom's Brass plugs back in.

I was very pleasantly surprised that my coolant changes seem to be working well. Very minimal corrosion, rust or scale inside the water passages. Not bad for 69 years.

And this was a motor that ran for about 3 years, sitting in my garage for the winters. It also has been sitting for the last three years getting ready for this restoration with coolant in it.



Bruce Cunha

Here is another hole.

Still planning to flush the water jacket prior to putting the new plugs in.

Bruce Cunha

Peter H.,

I use Three Bond Welch Plug Adhesive and Sealant available from Burson Auto Parts. Excellent, purpose made product. Also of course Tommy Lange's brass core plugs are used. They fit better in the initial stages compared to other suppliers.

Cheers
Rob Grantham
Rob Grantham

Great pictures. That really demonstrates the pitted and rough sealing surfaces. Those really need to be cleaned to bare shiny steel, and some sealant used even with Tom's plugs. I personally have had good luck with JB weld. It is also very easy to remove with a wire brush if needed. George
George Butz III

Loctite has a core plug sealant but very expensive in a BIG bottle.Here is a more reasonable priced and sized one!


https://www.vibra-tite.com/retaining-compounds/vibra-tite-550-core-plug-sealant-retaining-compound/
Len Fanelli
Abingdon Performance Ltd.
Len Fanelli

I looked for locktite today, but none of the automotive shops have it around me.

You are correct. Locktite 540 is expensive. $140 for 250ml. I did find a guy on ebay that will sell you 20ml for $14.

https://www.ebay.com/itm/Loctite-540-20mL-Retaining-Compound-I-BUY-BULK-SO-YOU-DONT-HAVE-TO/321213542716?hash=item4ac9d1b13c:g:cc8AAOSw1CBbt0fP:rk:1:pf:0


I found the Vibra-Tite 550 at $20 Bottle

https://www.vibra-tite.com/retaining-compounds/vibra-tite-550-core-plug-sealant-retaining-compound/

And

Permatex 26240 Which I found on ebay for $20. I went with the Permatex

https://www.ebay.com/p/Permatex-26240-Permanent-Strength-Threadlocker-Red-36-Ml-Bottle/1422661241?iid=283341317201&chn=ps

I also made some concave taps of sizes that fit the cups, to push the cups in better.


Bruce Cunha

RETRACTION
I started this thread with an endorsement of the Blue Devil product.
Either the product is useless or the gaps around my core plugs are to large for the product.
All seemed well after a few drives but the car has been sitting in the garage for two weeks and I just took a look at the engine.
I used a dye in the water and the photos work taken with a black light.
I had about 5 plugs leaking before and now see evidence of only two. However those two are significant.

Question:

Can I successfully remove and replace the plugs on the side of the engine without removing the engine from the car?

Would removing the right front fender make it possible/easier?
Mort


Mort Resnicoff

Second Plug is right behind the exhaust manifold but you can see the evidence.

The plug at the rear of the engine has never shown any evidence of a leak.

Mort Resnicoff

Mort - so sorry to see that you are still having issues. It is hard to tell, but it looks from your black-light picture that the core plugs are barely dimpled at all - certainly not enough to retain them. I suspect that has been your issue all along.

On a TF it is impossible to do so, but on a TC or TD you can insert/re-insert core plugs on the right side of the engine - just expect that it will be awkward because you have to have enough room to swing your hammer without damaging anything. You will have to remove intake and exhaust manifolds, and then things are pretty much open - just watch out for the fender. And hope the core plug in the rear of the engine is tight - if not, the engine really does need to come out for confident installation of a tight core plug in that critical location.

The first thing you must do is make sure that all rust and scale are removed from the engine grooves into which the core plugs fit. I use a junk screwdriver, file tang, wire brush on a drill, and anything else to clean out the hole - if there is ANY crud left in the hole, nothing will seat tightly in the hole. My brass core plugs are soft enough that they will fill in surprisingly-deep pits, when properly installed, and are guaranteed to be the right size - unlike others available, which are simply too small to fit reliably. Like almost any project in life, preparation is critical to successful, leak-free installation.

There is much written about installing core plugs - both here and in the other forum - the serious experts recommending using rods turned concave on the ends, of a similar diameter as the core plugs. Although they are certainly nice to have, based on my experience you do NOT need these dedicated tools for installing core plugs. The most comprehensible way to install them is to use two ball-pein hammers: rest one ball against the center of the plug, and then hit the flat end of that hammer with the other hammer. It may take two or three tentative hits, because you need to make a noticeable dimple in the core plug to get it to stay; my "tap" test helps identify ones that need a bit more settling. But you do need to be sure that you don't OVER-extend the dimple too deep, or use too small a punch, because the core plug will then begin to get smaller, and it will be loose in the hole.

Another "tool" I use is a socket on an extension bar, hit with a hammer; I use a 1/2" socket extension bar with a 3/4" socket against the core plug.

If you look at this link (https://mgtrepair.net/Plugs.html)
you will see one of my engines with core plugs installed; it was taken quite some years ago, and I would be unhappy that the large central core plug was so deeply dimpled, were I doing it now. Also, I would try to center my dimpling better. But that at least shows you what sort of attack is necessary. Less, and ANY core plug will come loose and leak.

Barney Gaylord, the MGA guru, confirms much of what I say and has good information on the process, and I refer you to it for another perspective:
https://mgaguru.com/mgtech/cooling/cool_105.htm

As for sealant use, everyone has his or her own way of doing things, and I have no intention of starting an argument with anyone or any process. In addition to the dimple some people apply a smear of silicone sealer in the plug recess before installation, in hopes that may fill in imperfections in the hole. Others apply a circle of J-B Weld to the outside edge of the plug after installation, hoping that it will lock the plug in place. Highly-respected John Twist recommends this use of J-B Weld (and my brass core plugs, thank you very much).

I don't use either of these steps, nor will either of them effectively seal a core plug in place if it has not been properly dimpled. Without them I have not had problems, but I understand why people might hope it helps. Chacqu'un a son gout.

I can say that 95% of the problems that (very few) people have had center around not expanding the plugs deeply enough. In most cases deeper dimples have worked fine, but in a few instances people have had to start over. The other 5% are from not cleaning out the hole enough before attempting installation.

Sorry this is so long. There are lots of videos on Youtube on "core plug installation," but be warned - the VAST majority show the installation of cup-type core plugs, not our dished-type. Be warned - they are completely different!

For an example of how NOT to install a core plug see https://www.youtube.com/watch?v=qCJErIE7yZ0;
his preparation and process are inadequate, and his tractor will certainly have leakage and problems with the install. For a better view see
https://www.youtube.com/watch?v=QHrzkGWC8Vs

I'm happy to answer any questions.

Tom Lange
MGT Repair
t lange

I totally agree with Tom, but I also feel obligated to suggest wearing safety goggles if you're going to hit two hammers together. Using hammers this way is extremely bad shop practice, but we all do it on occasion anyway. Just be aware that a nasty shard can come off one of those hammers faster than your eyes can react.

My choice of tools is a piece of steel rod slightly rounded on the end. I've also used a 1/2" extension on smaller sizes.
Steve Simmons

This thread was discussed between 28/01/2019 and 11/02/2019

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