4.2 Core Plug corrosion.....yuk!

I was just fitting the vacuum tank after powder coating when I noticed the RH centre core plug…!
Amazing corrosion. I just hope the block can be cleaned up once the plug is removed for replacement.
I am ordering replacement from SNG. Any hints or tips??

That’s grim.

What do the others look like?

I had continuing problems with the two core plugs behind the exhaust manifold that are on the cylinder head. I had replaced them twice and used Permatex stuff that is like tar and never totally hardens and they still leaked. After consultation with experts, I assembled them and used JB Weld and no leaks

Dennis 69 OTS

All ok…I’ve never seen anything like this one. It came out easy and there was a lot of ‘crud’ behind it. It has corroded out. The casting was ok thank goodness. The outside had been gummed up with something to stop it leaking!

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Been there, done that…
Thankfully the block was in perfect shape and all studs removed safely.

It can be done, don’t allow others to bring you down. These cars and motors have never let me down or ceased to amaze me.
I received many replies advising to scrap the block.

I have always had old Jaguars, and lemme tell ya, the removal of core plugs for proper cleaning of block is something i will do and recommend for all future jaguar purchases despite apparent exterior condition.

It should be added i feel to the xk engine cars FAQ etc I feel so strongly about it.

If it hasn’t been done to your knowledge, it must be done as far as I am concerned.

I’m convinced as well it is the cause of unknown overheating issues and other issues caused by resulting hotspots created.

I’ve discovered all the common flushing in the world will be very misleading and make absolutely no real impact.

Despite flushing the block ad nauseum, and the water leaving the block seemingly potable…I discovered precisely same as you!

As an aside, I had never done it on past cars i hadn’t rebuilt motors on and never had overheating issues.

After this, for me, from now onwards…it is going to be fundamental in my process.

Best of luck
Kind regards

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True, for ANY old engine.

When I rebuilt my Rover, just for the halibut, I removed both “core plugs” (one great big one, per side), expecting to find sludge.

Not a wisp was found!

That said, with Welsh plugs, it’s cheap insurance to R&R them.

Ah…I appreciate that…

Never done on past non rebuilt cars, mk7, etype, 3.8s, 2 xjs v12s…never had problems fwiw after bringing back from the dead…

Gotta say, after this experience it’s made me a believer though. .

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I broke my ‘core plug cherry’ and installed the replacement plug. I have been waiting to remove the inlet manifold for access and finally took the carbs off last night. I have used JB Weld as advised and used a large socket and extension bars to hammer home.

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Looks good from my house!

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What is the opinion on steel vs brass? I have seen both used.

What is the feeling on painted vs bare metal? Again, seen both.

Mine is as above - unpainted steel - but wondered if there was a perceived advantage in the other choices.

Good question…I would like to know opinion too

For the dished washer kind, Ive had good luck with brass: with the cup style, steel seems to drift in more tightly.

Ive not had failures with either.

Given the low miles, and regular coolant changes our cars see, other than aesthetics, I see no advantage with paint v. plain.

Stainless is or was evidently also available.

I obtained a long ago rebuilt engine that had been ignored with plugs out, and became seized

getting the pistons out was hell

same for the SS plugs, they were very hard, and dont want to deform inwards, without damaging the block lip

So I drill a hole and use a slide hammer…a regular drill bit would not penetrate then, used cobalt

I would not use them

I learned a lesson on this the hard way a few years ago, when I rebuilt the 1275 in my Mk1 Mini.

I found a socket that fit nicely INSIDE walls of the plug and knocked them in. The next morning, there was a tiny dribble of coolant running down from ALL FIVE plugs.

I then learned that a socket that fits inside the plug has the potential to deform the plug, and pull the walls of the plug inward as you drive it in, effectively shrinking the plug.

Since then, I’ve always used the back-side of a socket that is larger than the plug, so I am pushing on the “rim” of the plug. Then I drive them in, until the socket face makes contact with the block (flush), and I’ve never had a leak since.

Thats a very good point. Never thought of that. My only hope is that the socket was a perfect fit, so provided force very close to the rim. The JB weld should also fill any potential shrinkage. I will remember that tip for next time though