Oil leak??

I have had one nagging, small oil leak for a couple years now. The leak is where the vacuum pump connects to the head. I have replaced the oil ring type seal between the pump and head twice, to no avail. The oil is under the pump running down the cylinder head and then down the rear of the engine. It's a small leak but I am getting tired of it. Any ideas what I am overlooking? Thanks in advance.

Yeah, that one can be tough.

Make VERY sure you have the mating surface COMPLETELY clean (no oil on it!) AND pull the O-ring, clean the groove in the pump out VERY well so it is completely dry too. Yes, you need a new O-ring any time you disturb it, so get another one.

If there is ANY grit on the sealing surfaces it will leak a bit. It's impossible to get all the grit out without getting all the oil out and off, so basically the bottom line is that to get a leak-free seal you need completely, absolutely, utterly clean surfaces before you put it back together including the groove in the pump where seal ring goes.

And grease it before putting it together so you don't damage it. Vaseline works great for this.

Since you have already replaced the o-ring seal twice, the leak could also be coming from the vacuum pump nipple itself. It's somewhat misleading. If you remove the vacuum hose from the nipple and the nipple is loose and can turn, I bet that is where the leak is coming from.

It's been discussed here and I repaired mine using the JB weld method. Has not leaked since.