Changing xk 3.4 core plugs

[RichT]

Hi I thought I would post about this subject changing core plugs as there was no straight forward info when I looked and I got the wrong info from a well known parts supplier and initially fitted the plug the wrong way round with resulting coolant loss and undersell stripping fortunately on a very short run

To get it out carefully drive a decent sized screwdriver into the corroded bit about 10mm from edge as there is a machined lip around the hole in the block and then use a small block of wood as a fulcrum to lever it out unless you really deform the plug it should not drop into the block

on a mk 2 the core plugs are dished like a satellite dish they are fitted with the convex side out (raised side) out and concave (dished side) inside block.You then have to flatten the surface almost flat to get a seal. I also used a smear of araldite although some rec welseal or nothing

I used a 1/2 inch short tommy bar extension threaded with the bar so you can rain small blows on it with a 2 lb lump hammer side on without hitting your hand. I moved the socket carrier around the plug evenly to flatten the central 80% of the plug. I then for good measure strapped the core plug with a rob beer core plug strap and covered the whole thing in copper grease

If you try and use a big drift when you have limited swing on the hammer it doesn't seat the plug

I hope this helps someone save some time and steam cleaning the underside of their car with glycol.

as an aside I have ordered some expanding copper core plugs from the USA in case (which I guess is really when) another one goes in a more inaccessible place.

Of course this could all be grandma sucking edge territory for most!
All the best

Richard

[Martec]

I replaced mine as per your method(araldite) 13 years ago and keep a 45% level of antifreeze/ corrosion inhibiter and change it every 2 years. How is the smaller core plug at the bulkhead end of the entablature?

I'm intrigued by the 'Copper' core plugs as I would have thought they would expand and contract more than the cast iron block and so come loose?

Brian

[RichT]

Hi. http://www.dormanproducts.com/p-28443-568-011.aspx is the link to the copper gizmos I think you grip the big nut and tighten done the small one and it expands. I haven't looked at the small plugs although I have checked for leaks hopefully it will be alright til the summer when I can knock a couple of other plugs out and get the drain cleaner from my pressure washer in and wash out the rest of the crud from the block. I was thinking of carrying the copper jobs as an emergency measure for the bigger lower plugs

Cheers

Richard

[oldtimer]

Hi Richard,
Very interesting to read what you have to say. I hardly dare say that it must be over fourty years since I've changed that type of core plug. They were a pig then as they appear to still
be.
It never harms to resurrect these old topics and I am sure you will not be telling Granny and all that.
I am minded that down the years I have read many disaster stories of core plugs blowing out, even on newly overhauled engines.( Or espeacily after major engine overhaul)
As you will have discovered the machined hole in the block is tapered,the diameter increasing as it goes in and the angle on the core plug edge to match. Now, I am sure that who ever fitted these in the factory did not go around with a club hammer and a drift and give the plug a healthy thump!or did they. I would suggest that a press was used to deform the plug to designed amount to give the maximum interferance. What is the possibilty of exceeding maximum interference and start to reduce that critical load when using a big hammer. I don't know.
I have never found the correct procedure for this task

I have read antidotal evidence that if a core plug is dropped at 80-90mph the engine will be seized by the time you stop. If this is true the loss of a bit of underseal is nothing compared
to the catastrophy of a siezed engine.

I guess that people from some quarters will look down their nose at what I am about to suggest!
The fact is I have done it and it works and remains satisfactory.

Select two 3/16 inch bolts and lay them on the bench in a manner to form the letter T ,now weld them together. Cut the required amount off each side of the top of the T so that it can be passed into the water jacket. From memory one leg is longer than the other. Now drill a suitable size hole in the core plug for the leg of the T to pass through. Apply a smear of Red Hermatite or similar to the hole and plug, feed the plug down the leg of the T until correctly located. Next a fibre washer and self locking , tighten down to the desired amount. DO NOT cut off surplus bolt to aid removal. Fill with coolant , check for leaks.

Next time you have the engine out one may choose to revisit the problem when you have infinite access.
Richard,I'm just wondering if this will prompt any response , I can see one or two folks spitting feathers
Regards Oldtimer

[RichT]

That sounds like another great solution, it is all the better for the fact that it would really mess with the purists heads at a car show I would recommend painting the visible part of the repair dayglo orange or something.

I agree I appear to be lucky that my engine didn't seize although we will have to see if any long term damage as got quite hot but still running well, snow down here putting paid to any jag trips using my old sacrificial land rover at present. I m hoping that if it rusts the jag won't

Cheers


Richard

[oldtimer]

Hi Richard,
I have a feeling we could be singing off the same hymm sheet.
Especially the dayglow paint!
Happy motoring
Oldtimer