Oil leak from cylinder head - distributor plug

[antonyn]

Hi,

I've a leak on the 204L petrol engine, from the plug that fills the hole used for a distributor on earlier engines. On my last Saab, it was a matter of replacing the o-ring on the plug, which was held in by a bolt and bracket, but now the plug looks more like a interference fit "core plug".

Has anyone had experience of changing this type and if so, how did you get it out, & do you have to use any type of sealant when you fit the new one?

(BTW the EPC drawing still looks like the old plug!)

Antony.

[Max Headroom]

I have no experience of this myself - but if it isn't a huge leak, a temporary fix, that may last quite some time, and providing you have reasonable access to the offending leak, is to degrease the area as much as possible, and then spray clear engine lacquer over it.

I used this method to semi-permanently cure oil leaks on motorbike 'split' crankcases very effectively.

[antonyn]

So - for those who are interested, the "core plug" has a rubber outer covering. So I used a nail extractor (like the claw end of a hammer, but in screwdriver form) to ease out the old plug.
A smear of vasiline on the new one, and carefully drove it in using a socket. "Carefully" because there is no lip to stop it going right through!!

Antony.

[Max Headroom]

Vaseline??

Vaseline is petroleum based and will rot the rubber.

Silicone grease should be used

[antonyn]

Ahh - don't worry, I used a generic term - the actual product I use when assembling rubber parts is "Dow & Corning Plumba grease" as it is designed for o-ring assembly.

BTW - Oil is a petroleum product - is that why the seal failed in the first place?

[ScarbSaab]

Ahh - don't worry, I used a generic term - the actual product I use when assembling rubber parts is "Dow & Corning Plumba grease" as it is designed for o-ring assembly.

Yes, but Trenchfoot's probably thinking of others with less experience. Consider that someone else searching on the forum might read it and think "I've got Vaseline(TM) in the cupboard" and use it!

[Max Headroom]

In my 35 years of engineering experience, in all cases that I know of, only silicone greases should be used where they come into contact with rubber or plastics.

Flexible oil-breather pipes, O-ring seals etc are manufactured with resistance to the specific petroleum product that they are likely to be in contact with.

Seal compatability guide HERE

[BOF]

You're quite right, but as the man said, oil is a petroleum product, and a lot of rubber pipes and hoses on cars come into contact with oil all their working lives. It's all down to the the specific rubber compound that the plug is covered with; it might well be resistant to Vaseline as well.

B.O.F.