240 GLT saloon restoration project

[Bugjam1999]

Take the plug lead off cylinder 3 and put as much talcum powder into the sparkplug recess as you can, then put the plug lead back on.

Have someone else start the engine and see if the talc gets blown out of the recess.

Any excess can be washed away with a hose (once the engine is cool).

Cheers

[Juular]

Originally Posted by Bugjam1999

Take the plug lead off cylinder 3 and put as much talcum powder into the sparkplug recess as you can, then put the plug lead back on.

Have someone else start the engine and see if the talc gets blown out of the recess.

Any excess can be washed away with a hose (once the engine is cool).

Cheers

That's an excellent idea!

My plan was to seal the thread with a bit of blue threadlocker, but your method is much simpler.

[Laird Scooby]

Originally Posted by Juular

That's an excellent idea!

My plan was to seal the thread with a bit of blue threadlocker, but your method is much simpler.

Threadlock (in any colour) will act as an insulator between the spark plug thread and the head resulting in more misfires. If the thread is found to be leaking (blowing-by) the best thing would be to Helicoil the head. Sometimes this can be done in-situ although if it's on #3, there's not much room there with the servo and other things in the way. Even moving those things out of the way won't make it much easier as the plugs go in at a strange angle so better to remove the head.

[Juular]

Originally Posted by Laird Scooby

Threadlock (in any colour) will act as an insulator between the spark plug thread and the head resulting in more misfires. If the thread is found to be leaking (blowing-by) the best thing would be to Helicoil the head. Sometimes this can be done in-situ although if it's on #3, there's not much room there with the servo and other things in the way. Even moving those things out of the way won't make it much easier as the plugs go in at a strange angle so better to remove the head.

In this instance I was planning on just doing the top 20% of the plug as it should be enough to at least seal the threads temporarily without insulating it from the block.

The powder idea seems more conclusive anyway.

[Laird Scooby]

Originally Posted by Juular

In this instance I was planning on just doing the top 20% of the plug as it should be enough to at least seal the threads temporarily without insulating it from the block.

The powder idea seems more conclusive anyway.

Threadlock has a habit of creeping around all the threads though, one of its properties that make it such a good product, just need a couple of drops and they work their way arond and along the threads.

The talc is a good idea though, just need to be careful it doesn't shake off with engine vibration but you should see a puff of it as the engine starts if that is the problem.

[Bob Meadows]

https://www.amazon.co.uk/Draper-5176...713717269&th=1

A spark plug thread chaser may just correct the threads:~
Bob.

[Bugjam1999]

A while back I helped a friend change the cylinderhead on his 244 as the thread for the sparkplug for number 4 had been stripped by a not very careful garage. The conclusions we came to at the time were- helicoil aren’t good enough for a sparkplug, a timesert might be good enough but they aren’t cheap and required more access to fit than we had (there might be space for number 3, but there wasn’t for number 4) and finally the cost of a replacement head was low enough that we just swapped the head for a good one.

If it does turn out to be the sparkplug thread, a good used head might be the way to go.

Cheers

[Bob 1967]

It's always an idea to put some copper grease on the spark plug threads to stop them seizing/stripping threads . Dissimilar metals and all that. I only tighten them wrist tight.
I have come across a motorcycle head where some doughnut epoxied the plug in, it was scrapped.

[loki_the_glt]

Originally Posted by Bob 1967

It's always an idea to put some copper grease on the spark plug threads to stop them seizing/stripping threads . Dissimilar metals and all that. I only tighten them wrist tight.
I have come across a motorcycle head where some doughnut epoxied the plug in, it was scrapped.

I'm guessing he didn't want to lose the plug if the engine back-fired then?

[classicswede]

Helicoils are not suitable for anything you need to take apart again so do not use one for a spark plug

The Timesert do work well and must have repaired over 100 threads with them. The worst thing that happens with them is they come out with the plug but you can just screw in a new one to sort it