M20 Oil Return Pipe Leak

[knapmann]

Is there a trick to getting the return pipe from the manifold to the block to seal properly at the top (manifold end)? I have installed new O-ring and covered it in sealant and it is still leaking significant oil! I'm getting very fed up with it to say the least!

[Brianmoooore]

Sealant???? It's silicon grease you should have used, not silicon sealant!
No tricks required - just everything assembled on the tube in the correct order, well lubricated, and pushed home.

[reggid]

yeah i just use some oil to lube the o-ring. if you dont lube the o-ring you can tear it. no sealant is necessary.

might be some crud stoping the o-ring from seating properly.

also you have use a gasket between the head and manifold? if there isnt a gasket the tube sometimes doesnt align 100%

its also not the oil return tube its the crankcase vent tube.

[knapmann]

Thanks guys I will try some silicone grease, I have replaced the O ring once already it is definitely not damaged, I used a proper BMW one to make sure it was right and it leaked lots of oil, yes I have a gasket on the manifold-head, I still think it must be some kind of alignment issue but there is no adjustment. The manifold port was properly cleaned on install, I dont know what more I can do other than use some kind of gunge to plug it, the o-ring alone is not working. Maybe I could double o-ring it?

[e30topless]

can you get a pic, you do have the spring in place and the tube is the right way up ?

[knapmann]

Yes the tube is the correct way up, I dont think you could actually install it the wrong way around, It has the spring washer and o-ring at the bottom. I *might* have fixed it now, I found a thicker walled o-ring than the stock one and fitted that, it was a tighter squeeze to get the pipe to seat into the manifold but after 20 mins of running I have no oil *yet*.

[knapmann]

Ok, so its not fixed, I HAVE fixed the oil coming from the top of the tube at the manifold and running down, but there is oil coming out at the base now, (when the top was leaking down the tube, it was impossible to tell it was leaking from the bottom as well). So this is a full manifold off job now as its impossible to get at or renew the lower o ring with it in place (even though it was a new one).

Who's betting I spend an entire day renewing one o-ring and as soon as I start the engine it still leaks oil.

I have to say this vent tube is a piss-poor design, whoever came up with this idea wants shooting

[Brianmoooore]

Are you sure that the tube hasn't been damaged, possibly by some previous 'mechanic' trying to remove or refit it with the manifold in place.
The tube is clearly an adaptation on an earlier M20 design, but as long as it is fitted with new O rings every time it is removed and the bits are assembled in the correct order, it should be 100% leak free.

[knapmann]

I dont know if it makes a difference but the engine is stroked to 2.8l. I would have thought that any positive pressure would blow out of the rocker cover breather rather than force oil out of places. What other ventilation of the crank case is there? other than rocker cover vent? Haven't done a leak down but my compression is 170-180psi. The tube is not damaged, I installed it myself. I was sure not to nip the o-ring, installation of the tube is hardly rocket science (push down tube, place on manifold, release tube), I dont understand why its leaking tbh, I could understand it leaking from the top but leaking from the base seems counterintuitive.

[Brianmoooore]

Where does your rocker cover vent connect to?