Core Plugs

Ian Anderson

Lifetime Supporter
I had the Dax Gt40 in for its annual MOT last week and it came out with an advisory....... again.

they report a core,plug is leaking and it is the same one replaced by the garage a year ago at last MOT and that the one further back on the block on the same side has started weeping.

The core plugs are for the coolant system. The big leak one has been replaced about 5 years back too so the same one has gone twice!

Engine is the Rover/Morgan aluminium block.

So question to the engine gurus,
Do you suggest sealant when installing these plugs?
If so which sealant?
Do the holes need to be reamed out or similar? Or the bore “roughed” with sandpaper to help sealing?
or should I be sending it away to get screw in plugs fitted?

And can anyone suggest why this keeps happening?

thanks in advance
Ian
 
Original plugs were aluminum, hope your not replacing with steel or brass, the block will expand more than the plugs. Pretty sure the ones I removed from an engine a few years ago had a sealant similar to hylomar on them. Inspect the opening in the block to check that bore surface was not damaged by the removal of original plugs.
 

Ian Anderson

Lifetime Supporter
Thanks Jimmy
it is Rover Morgan TVR block, aluminium derivative of the Buick years back.

Those sound to be along the lines that Jac suggested!

I asked,on the Rover forum and it is a reasonably common fault and ‘rust’ through.

it also seems like the feeeze plugs supplied by different manufacturers can vary in Diamerer by 7 thou on the inch and half nominal size!

ian

ian
 
Thanks Jimmy
it is Rover Morgan TVR block, aluminium derivative of the Buick years back.

Those sound to be along the lines that Jac suggested!

I asked,on the Rover forum and it is a reasonably common fault and ‘rust’ through.

it also seems like the feeeze plugs supplied by different manufacturers can vary in Diamerer by 7 thou on the inch and half nominal size!

ian

ian
No Jimmy gets all the credit for his find of the screw in version, sounds like a good deal & able to hire a 'tap' to prepare the block for them. Anodising should see them last forever.. I was just thinking, outboard motors for boats used to run a tab/ anode on the prop housing to avoid corrosion.
 

Kevin Box

Supporter
If the block is a little corroded or worn from previous attempts, it would be easy to get a machine shop to make you a slightly oversize aluminum one.
I have made them before based on the steel ones. As far as i remember I went for 4-5 thou interference and just put them in the ice box to cool before fitting.
The main thing is not to make it too thick so it has some compliance as the block heats and cools.
Hylomar works well but if you don't have it automotive RTV is fine.

cheers

KB
 
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