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MG TD TF 1500 - John Twist new video on freeze plugs

John Twist is back on Youtube showing how to use JB Weld to weld in freeze plugs. Isn't the purpose of the plug to prevent a cracked block if the coolant freezes and expands? Huh?

http://www.youtube.com/watch?v=Nls6xf6L0i4&t=3s
efh Haskell

NO!
The should be called “CorePlugs”.
They cover access to holes needed in the casting for various reasons. Such as cooling passages and excessive weight.

They let sand out of the casting after cooling.

Jim B
JA Benjamin

With all due respect, opinions differ on this subject. I have certainly received disgruntled e-mails from people who struggle to remove all traces of old J-B Weld from the core plug openings when rebuilding an engine - hot tanking and other shop cleaning processes do not generally remove it. Since removal of absolutely every trace of rust, corrosion and old sealant is the key to successful installation of new core plugs, using J-B Weld feels like a drastic path to follow. (And using steel core plugs that rust, although cheaper, is inviting early failure in an XPAG engine.)

One fellow in New Zealand even broke a chunk of metal out of his block while using a cold chisel to remove old J-B Weld that had been smeared around a core plug, and was forced to have his machine shop properly repair the lip in the hole to return it to its original configuration.

In my experience, having sold literally thousands of brass core plugs (and installed hundreds of sets), there are two reasons why a core plug leaks: the hole has not been completely cleaned of rust and debris, or the core plug was not properly or sufficiently dimpled to fit. Because of the design and manufacture of the XPAG/XPEG block, the casting hole in which the core plug sits almost never corrodes to the point where a core plug cannot seal completely, without the need for supplementary sealant.

With my correctly-sized brass core plugs, a clean hole and careful installation, core plugs will neither leak nor pop out (other brass core plugs on the market are NOT correctly sized, and DO pop out...). Please see mgtrepair.net for more information.

I have tremendous respect for John Twist and his professional work as a problem-solver and mechanic (our friendship and working relationship goes back some 50 years), but I respectfully disagree with him on this point. Of course, your mileage will vary...

Tom Lange
MGT Repair
t lange

And another opinion.... I use the JB weld along with Toms excellent brass plugs. With a good number of the blocks, the area around the plug opening has been corroded over time and the only way to get a quality seal with the normal sealants would be to have that area machined and use oversized plugs. That ain't gonna happen for most of us. I also use some Permatex sealant when installing the plugs and after words give the seam a coating of JB. There is no reason to use a chisel to remove the coating if needed. I have used a 4" grinder with a wire wheel and it will easily remove all traces of the JB weld.

John knows better than to refer to the as freeze plugs. They are core plugs. I can attest to his failure using silicone as the TD I had came to me with an engine his shop rebuilt in the mid 90's and the core plug behind the exhaust manifold fell out during a drive not that long after I installed the engine in the car.
L E D LaVerne

I wonder if JB Weld has changed over the years? When I have removed it, it is just like a hard plastic and not that big a deal. A well known MG person in the area had the rear plug pop out during restoration test drive on a TF a few years ago. He now always uses JB weld. Silicone sealer is useless, and coolant will leak under it. Some car I did the plugs on had a couple badly corroded irregular plug openings, no way they would seal without some sealer. Thankfully Tom's plugs are thick, the correct diameter, and fit beautifully. I would use his with the JB weld in the future. I have one of the paper thin ill-fitting ones in the back of my TD block from years ago, so far so good. George
George Butz III

All this I started by using the word "freeze" rather than "core"!
efh Haskell

On TD and earlier the cooling system is non-pressurized. So there would have to be serious corrosion or an improperly installed plug to suffer leaks. I would only use JB weld as a last resort to fill corroded areas and then sand smooth. Never to actually seal. The plug is held in place by expanding it, not by any type of glue.

On pressurized systems I have used locktite on rare occasion, but only when necessary.
Steve Simmons

I always use steel core plugs and locktite - never had a plug blow. leak or rust out.

Cast iron are next to each other on the galvanic series, brass is much higher in the series. The brass will not corrode but the cast iron will!

Use the correct proportion of antifreeze in the coolant and neither cast iron nor steel plugs corrode.
Chris at Octarine Services

From Wiki: Core plugs are used to fill the sand casting core holes found on water-cooled internal combustion engines. They are also commonly called frost plugs, freeze plugs, or engine block expansion plugs.
George Butz III

I think the confusion starts with the use of the name expansion plugs
To me this means that they need expanding during fitting to get a tight fit but it could mistakingly be taken that they are there to blow if the coolant freezes and expands---If the water freezes it isn't going to be able to travel and find a plug to blow out, it'll just crack the block instead
I hate JB weld on W/plugs
and the video shows a messy looking job to me, not what anyone I know would do
I usually clean the hole out as clean as possible, wipe a smear of Loctite flange sealant around the corner of the step in the block, fit the new brass plug and almost flatten it out
never have an issue
William Revit

Technically they are Welch plugs, and it is slang to call them "freeze plugs." In the event of a hard freeze, the block will crack before the plugs pop out.

Tom Lange
MGT Repair
t lange

A good cleaning with a dremmel type tool wire brush and if really bad, flat round grinding stone can get the lip looking great. Even if JB was used.

I use tom's brass plugs with loctite 540 core plug sealant. It is very similar to the adhesives used for bolts.

I also use a specially made (by me) aluminum dowl with a concave end that is close to the angle of the plug.

This allows the plug to push in so it is near flat. Expanding it to its max.



Bruce Cunha

In my days we used *litharge mixed with glycerine never had one fail

* spelling?
George Mills

I have experienced great success with Tom Lange's brass Welch plugs.
I do also use a sealant SPECIALLY designed for sealing these plugs i.e.
Three Bond brand Welch Plug Adhesive and Sealant.

I agree with William and Bruce in that the plug has to be worked over evenly to an almost flatter form compared to many examples over the years I have seen.

Cheers
Rob Grantham
TF3719("Aramis"),TF9177("Athos").
Rob Grantham

New car manufacturers recommendation to dealers and professional engine builders as well recommend Loctite 540, or other sealant specifically made for core / welsh plugs.
Len Fanelli


OK, I'm the odd man out! This is what I've used for years and it works. A little on your finger wipe a very small amount in the previously cleaned core plugs seat, just enough to color it, install the plug and done. Installed Toms brass plugs in the TFs engine 6+ years ago and still no leaks anywhere. The seat has to be rotary brush/polished clean. PJ


PJ Jennings

In my experience you don't really want a "dent" or bend of any kind. You want to flatten the face. This gives the greatest amount of expansion with the least amount of bending. I use a piece of 1" solid steel rod (or maybe it's a bit smaller, can't remember) with the edges slightly rounded. It doesn't take much on an XPAG to seal it up. There is zero pressure on TB/C/D and low pressure on TF.
Steve Simmons

This thread was discussed between 23/10/2019 and 28/10/2019

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