18 replies to this topic

[DClarke1954]

Hi folks,

 

I am kinda new to classic minis so please be gentle.

I seem to have a persistent oil leak in one plug well (#3)

It doesn't seem to be coming from the rocker cover gasket and tracking downwards; when you remove the plug it is oily all round the base and there is oil in the spark plug well.

Can compression & combustion force oil back up through the spark plug threads and into the well?

If I remove the plug and remove the oil there the plug seat looks fine, no cracks etc. (see pic).

So what is causing this?  Valve stem oil seals gone kaput on this cylinder?  Engine totally knackered?

As a newbie spannerer, what's the fix if the cause is obvious to you all?

 

Many thanks in advance,

 

Dan.

 

 

[Chris1275gt]

Looks to me that it’s coming from the rocker gasket above with the darker stain than the others. It wouldn’t be coming from the cylinder as the exhaust would be smoking like a goodun.l

Edited by Chris1275gt, 09 June 2025 - 03:50 PM.

[Avtovaz]

looks to me its comming from teh plug, it looks like is spattered up the rocker cover too. make sure you are tightening them enough, use a torque wrench if not sure to do it by feel. 

[DClarke1954]

Looks to me that it’s coming from the rocker gasket above with the darker stain than the others. It wouldn’t be coming from the cylinder as the exhaust would be smoking like a goodun.l

Good point.  Well there doesn't seem to be any smoke (not that I can see in my rear-view mirror) or if I rev the car with my leg through the open door.

 

I will see if I can tape a tell-tale piece of white paper on the block from the rocker cover to the plug-well.  Thanks! 

[DClarke1954]

looks to me its comming from teh plug, it looks like is spattered up the rocker cover too. make sure you are tightening them enough, use a torque wrench if not sure to do it by feel. 

Well, they all get tightened the same, and it is the only one leaking, but I will get Mr. Torque wrench out and check how tight it is.

My manual "by hand/eye" method is to screw them in till it comes to a stop the put the ratchet on the socket and give it 1/4 to 1/3 of a turn till it feels as tight as it want to go.  Thanks! 

Edited by DClarke1954, 09 June 2025 - 04:47 PM.

[bpirie1000]

Also an option for putting some form of dusting over the block. Flour or plaster dust then will show you where the leak comes from.

[nicklouse]

Rocker cover gasket.

[DClarke1954]

UPDATE:

A strip of newspaper taped at either end to the surface of the block below the gasket line and directly above #3 cylinder remained clean and dry while the plug-well got oily.

So that suggests it is coming from the cylinder out of the threaded plug hole doesn't it?

But there is no blue smoke (or any appreciable smoke at all) from the exhaust.

I am mystified.  I shall swap plugs over to see if it moves with the plug, but I think I may have already done this (not sure).

 

Q. Can you buy new washers for spark plugs?

[nicklouse]

So it is collecting in the spark plug well.  It is coming from the rocker cover.

[Lplus]

UPDATE:

A strip of newspaper taped at either end to the surface of the block below the gasket line and directly above #3 cylinder remained clean and dry while the plug-well got oily.

So that suggests it is coming from the cylinder out of the threaded plug hole doesn't it?

But there is no blue smoke (or any appreciable smoke at all) from the exhaust.

I am mystified.  I shall swap plugs over to see if it moves with the plug, but I think I may have already done this (not sure).

 

Q. Can you buy new washers for spark plugs?

How old are the washers and how often have the plugs been removed?  I've found the same sort of seepage past extremely well used crush washers but generally it isn't sufficient to cause me grief.  Washers are available, eg - Spark Plug Washers - Spark Plug Accessories - Ignition - Electrical

 

[DClarke1954]

So it is collecting in the spark plug well.  It is coming from the rocker cover.

Nope.  Tested for that with a strip of absorbent paper taped in place. 

 

Thanks anyway.  

Edited by DClarke1954, 10 June 2025 - 12:57 PM.

[DClarke1954]

 

UPDATE:

A strip of newspaper taped at either end to the surface of the block below the gasket line and directly above #3 cylinder remained clean and dry while the plug-well got oily.

So that suggests it is coming from the cylinder out of the threaded plug hole doesn't it?

But there is no blue smoke (or any appreciable smoke at all) from the exhaust.

I am mystified.  I shall swap plugs over to see if it moves with the plug, but I think I may have already done this (not sure).

 

Q. Can you buy new washers for spark plugs?

How old are the washers and how often have the plugs been removed?  I've found the same sort of seepage past extremely well used crush washers but generally it isn't sufficient to cause me grief.  Washers are available, eg - Spark Plug Washers - Spark Plug Accessories - Ignition - Electrical

 

All the plugs have been in and out numerous times; only this one leaks.  As above, I will swap 2 plugs and see if the leak moves.  Thanks. 

 

[Gaz66]

This reminds me of when I rebuilt my 1071 motor, fitted it in the car and filled it with oil.
Just about to spin it over to get oil pressure up when I see the pool of oil working it's way out from under the car.
A quick look sees it pouring out of the diff output cover seal so drained what was left of the
oil and proceeded to remove the cover to look at the seal then I saw it, a trail of oil from the back of the rocker cover, down the back of the block and pouring off the side cover. 😁

[amsgw]

Spark plugs are positioned to sit with the sparking end inside the combustion cylinder - that's how they ignite the air/fuel mixture and how the engine turns over. The only way you would have oil originating from the spark plug hole itself would be if it is blowing past the piston rings, into the combustion chamber and out of the opening. If that were the case you would absolutely know, as it would be running rough as anything and coughing blue smoke.

I would be very willing to bet it's from the rocker cover gasket, and that's arguably the easiest and cheapest repair you're going to get on a mini!

I know you've said you've tested for it, but if you've only taped paper at one end and the other and then driven, I reckon your paper has flapped about a bit and perhaps missed a drippy leak

[Gaz66]

Dust some flour over the area and see where it sticks. As long as the rest of the head isn't grimy