Oil leak from Manifold to exhaust joint.

[John Boy]

Hi all,
as above really, oil is leaking from the manifold joint and dribbling down the exhaust. its a 1098cc, breather pipes are clear, no other leaks anywhere else as far as i can see, its had a new head gasket recently/ new tappet cover gaskets, everything torqued back up in order, .....wondering if theres a head gasket issue somewhere that i'm missing?
Anyone any ideas?

Cheers
John

[svenedin]

Hello John,

There are multiple types of breather on these engines. What type do you have? I have (1969) the chimney tappet chest cover type and a pipe to a PCV valve on the manifold. I did have a weep on the inlet ports (because this is where oily fumes go in from the breather) but this was just a tired old manifold gasket and it was sorted with a new one.

Another time I did have a head gasket leak and that was also on the manifold side of the engine.

I would check:

1) Rocker cover gasket. This can bow outwards and distort if the rocker cover is tightened down too much. The cover should only be tightened to 4 Lb ft.
2) Condition of manifold gasket and mating surfaces and torque of manifold nuts (15 Lb ft)
3) Tappet chest gaskets (which can be fitted incorrectly or squashed by too much torque) and the rubber cup washer under the securing machine screw (2 Lb ft)

If all of those are fine then it may well be from the head gasket. Mine leaked slowly for many many months before I got round to doing it. You may get a better view of where it is coming from with the manifold off to inspect the gasket.

Good Luck!

Stephen

[John Boy]

Appreciate the reply Stephen, i'll get to work.
Many Thanks
John

[John Boy]

https://photos.app.goo.gl/ZWHDp7jrucyPWzAo6

Something not right here me thinks!

[svenedin]

Hmm. Well it's an exhaust port. Does the engine have symptoms of burning oil? Blue smoke under load or blue smoke when revved after idling for a time or at start up?

I do see oil on the INLETS on my engine (blow-by that is going in from the breather) but not on the exhaust ports.

Looking at your photo the mating surface for the gasket is far too mucky for a gasket to be making a good seal. I would be inclined to take the manifold studs out and clean up that surface really well and fit a new gasket. You would also need to clean up the mating surface of the manifold.

Hopefully the engine experts will be along to offer further advice.

Stephen

[oliver90owner]

First? Check your plugs. That should tell you something. If oil is leaking into the exhaust port(s) like that there is internal trouble. It is either flooding down the exhaust valve guide(s) or passing the piston(s). A compression test might be illuminating.

Your pic indicates there is nothing leaking from above; oil will not climb, from a head gasket, into the exhaust port. Looks expensive.

[John Boy]

Thanks all, I shall investigate!

[svenedin]

First? Check your plugs. That should tell you something. If oil is leaking into the exhaust port(s) like that there is internal trouble. It is either flooding down the exhaust valve guide(s) or passing the piston(s). A compression test might be illuminating.

Your pic indicates there is nothing leaking from above; oil will not climb, from a head gasket, into the exhaust port. Looks expensive.

Yes. I was thinking blue smoke under load suggestive of bore wear. Blue smoke at start up or when revving after idling suggestive of worn valve guides. Compression test would be interesting. If only one cylinder has low compression it might be a piston ring or a valve that’s leaking.

Stephen

[philthehill]

If the compressions are reasonable then I would suggest a worn exhaust valve guide and worn valve stem is allowing oil to pass down between the valve stem and guide. Replace the valve guides and valves (if necessary). Fit top hat seals with the correct grooved valve guides to the inlet valves only.
The crud on the manifold faces is typical of a 'A' Series manifold to head joint when the manifold to head is split apart.
Greasing the manifold gasket before fitting makes for a nicely sealed joint and the gasket can be removed easily without leaving any crud behind.
As regards a seal on the exhaust valve guide I would recommend that one is not fitted. The exhaust valve stem needs the lubrication when using unleaded E10 fuel. New guides and valves (if necessary) will be sufficient to keep the excess oil where it belongs on the top of the head.

[John Boy]

https://photos.app.goo.gl/xeZn5Vvkse5DkQsw8

Compression is this across all 4 cylinders... No difference.

[philthehill]

Those compression figures are acceptable so in that case I would recommend that you replace the valve guides with the correct length grooved ones and top hat seals for the inlet valves and plain guides for the exhaust valves.
Check for wear on the exhaust valve stems.

[John Boy]

Those compression figures are acceptable so in that case I would recommend that you replace the valve guides with the correct length grooved ones and top hat seals for the inlet valves and plain guides for the exhaust valves.
Check for wear on the exhaust valve stems.

Thanks for all your help mate, it's appreciated