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MG TD TF 1500 - Core plug replacement

Hi guys
The large core plug at the back of the engine is leaking and needs replacing. I have read on the archive about cleaning, sealing and inserting the new core plug. My question is has anyone replaced this core plug without removing the engine and if so any guidance would be appreciated.
Thanks in anticipation
Regards
Mick 52TD
Mick Cook

I did but had to change to the cup type freeze plug from the dish type since you cant get a hammer in place to spread the dish.

I chilled the cup in liquid nitrogen to shrink it to a slip fit, then using two pair of small tongs inserted and held it until it expanded on warm up.

Wear gloves and be sure no cold parts touch skin. It was a bear to manipulate into place. I dropped it 4 times before final fit.

It has now been in place for 12 years with no leaks

Don Harmer

You can also remove the floorboards and the metal lower firewall/toeboard for access. Or drill a hole in the toeboard. George
George Butz

I would check all 8 core plugs, as when one becomes punky it means that circulation has been sluggish at that point, resulting in rust in the cooling passages. The engine will undoubtedly benefit from a thorough flushing, and all core plugs ought to be replaced.

I sell brass core plugs, guaranteed never to rust or rot.

Tom
t lange

Mick, You might be able to save yourself hours of labour by fabricating a small pressure screw device from a hex bolt and nut which could be placed between the firewall and the centre of the core plug to install and form a 3/4" dia. dimple about half the depth of the dome surface to expand the plug and seat it. Removing the old plug first should not be that difficult. Just puncture it with along pick in the centre and lever it out. Cheers Phil
Phil Atrill

Mick,

If empathy is of any use, I have a weeping core plug in exactly the same place, and I'm wrestling with the same issues. The PO bodged it up with silicone, which I found, removed, (and then bodged up with something a little more substantial). However, water will out and following 18 months dry there's the slightest of drips now showing, so I'll really have to do something permanent about it.

I don't want to take the engine out, so I'm looking for another option, too. I've no access to liquid nitrogen (I'm amazed over what you can still get hold of in the States - the Health and Safety Brigade would be in fits, here!), don't really want to start dismantling or cutting holes in my firewall, so I quite like the idea of the "pressure screw device". I do have some of those rubber plugs, which compress when you tighten the centre bolt, but I've read iffy reviews about the long-term use of these.

Are there any other views on this? It has to be a permanent repair but isn't it really a matter of getting the core plug properly seated and sealed and won't steady pressure do that as well as an impact method? There's no water pressure on the plug when it's in use, so I'd have thought the forces wouldn't be that great.

As ever, all views are gratefully received.

- Tom.

(On a perfect day for a long drive - dry, very sunny and warm)
Tom Bennett - 53TD 24232

Thanks guys
Your advice as always is usefull. I do have a large rubber grommet in the firewall directly in line with the core plug so one of the PO may have had similar problems. Have filled the radiator with Bar's Leak Seal as a temporary measure and will look at a more permanent solution when the weather gets worse, it's too nice here at the moment to bne working on the car. Will always carry can of water with me!!!
Mick 52TD
Mick Cook

Tom, I think the pressure screw idea will work just as well, if not better than using a ball peen hammer, as you will have better control as to where the dimple is applied. Also you should back up the firewall end with a steel plate, so that you only dimple the core plug. I would also use some "weld bond" on the perimeter to help with seal.

Phil Atrill

I'm actually working on such a tool, as we speak!

Tom Lange
Brass Core Plugs-r-Me
t lange

Guys, that is a brilliant idea. Until restoration, my TD had the 1/2" hole we drilled back in the 70s to replace the plug. George
George Butz

I'm having trouble picturing the screw equivalent of the F=mA developed by the abrupt deceleration of a hammer. IMHO, dimpling a core plug requires a good bit more force than can be obtained statically. Bud
Bud Krueger (TD10855)

I have NOT done it, but my PO obviously had! And I know the engine had NOT been removed. So it can be done, just to commiserate. Hang in there!
Ed
efh Haskell

I've done it befor. Took less then 10 minutes.
Used a Nut coupler.
Two bolts threaded into each end. Then just used a couple open end wrenches and twisted.
You can cut the head off the one bolt that is up against the pug so it will make a smaller dimple.
Place a backing plat against the fire wall so you don't dimple it, I used a block of wood.

G D

Hi GD,

Thanks for the useful info. - just one point, bearing in mind the large size of the core plug, wouldn't you want to use the head of the bolt up against it? What diam. bolt did you use?

Thanks again,

John
J C Mitchell

I'm with Bud. Although the F=mA isn't entirely analogous. First off, simply dimpling a core plug, even with a hammer blow, doesn't create a seal if the core plug is dimpled in without changing its outer diameter. It simply gets a wrinkle like a snapshot of a ripple from a rock thrown into a pond.

Core plugs need to be flattened to expand into the opening. A good way is to use a mandrel approximately half the diameter of the core plug, such as a second double flat faced hammer. I have been known to add a small seam of JB Weld to the edge of a core plug and allow it to dry for several days to aid in the sealing and adhesion of the plug. If the resulting installation with a screw devise didn't result in a flattened plug, but instead a rippled/dimpled one, I would be concerned.

If there is excessive corrosion and problems in the block, as much blockage needs to be removed as possible before removing the leaking plug. I feel my block and radiator are pretty clean, and on a summer day (85 F) I run 90 C at 4200 RPM in top gear on a long haul (several miles). I calibrated my gauge at 100 C prior to installing it. In town or under less demanding load I'll run in the low to mid 80 C. I would run with less antifreeze to enhance the heat transfer, but in Minnesota with unheated storage I need the freeze protection. If any aluminum parts are in your cooling system (radiator or aftermarket water pump) you still need to run ethylene glycol based antifreeze, but it MUST be flushed and renewed every two years without fail.

I hope this helps,
Dave
Dave Braun

The correct method of expanding a core plug is to create a dimple 1/2 the depth of the plug's curvature, which is what I recommended in my previous post. The plug should not be flattened. A pressure screw can easily exert up to 5 tons of pressure, and will do the job just fine. Phil
Phil Atrill

This thread was discussed between 02/07/2011 and 04/07/2011

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