Excessive smoke from oil filler cap. ?

Hi all, was hoping the recent gearbox/clutch change would be the last of my worries for a few months, yet a day or two after, I noticed a lot of smoke in the cab! After investigation, it is coming from oil filler, I have replaced rubber gasket, now oil is coming out of the breather/mushroom on the top of the engine. I have checked breather pipes, and cleaned mushroom, but I suspect one of two things, after looking at forum posts... Head gasket, or piston rings? There is no mayonnaise present, but it has been running rough, and has been impossible to cure with timing or carb adjustment.
Am I looking at a rebore? Replacement rings? Valves? Or something a little easier on the pocket/time?
Cheers.

take head off and check gasket especially for dark areas in fire ring contact surfaces showing signs its leaking ,a clean ring around each cylinder will show its not leaking ,bores will probably be worn and best cured with rebore and new pistons £200 ish for both new bearings etc

Thanks james, is there anyway of testing for this without the head off, considering it is daily runner? Cheers.

compression test

Ok will do, thanks.

you would normally expect readings to be slightly lower at going toward rear ,but for instance 2 and 3 been lower would indicate blowing between the two

jamesmartin said:

compression test

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Surely that wont wont help to know whether its head gasket or not though?

Ok thanks. Will find someone with one, as I prob don't need to buy tester?

How long would mayonnaise take to build up if head gasket had gone? I remember first car I drove had it from day one! Hillman hunter! (pass down)

depends where the gasket is gone.....you might not get mayo at all

not long but can build up on older motors as normal head gaskets dont allways go to water way often series just between two cylinders,

Oh, cheers. I learn something new every time here. Thanks. I do try to pass on the little I know too when I can... When I can get my head out from under the bonnet!

blue beasty said:

Surely that wont wont help to know whether its head gasket or not though?

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course it would ,as said normally further from water pump compression is reduced ,if 2 cylinders are down normally head gasket ,1 cylinder a broken ring ,valve not opening

I guess thats a fair enough assumption.....not arguing just interested. I suppose the chances of a combination of rings and/or valves on more than 1 cylinder are pretty remote though if it was running rough and then got worse its possible.

Academic anyway I guess cause the cure needs the head off anyway

im not either maybe my style seems so ,but is true that normally you take the event that 2 cylinders next to each other having a failure remote ,but is still possible ,its what makes making diagnoses sometimes difficult as you rely on correct info ,i suppose you use logic and statistics

jamesmartin said:

im not either maybe my style seems so ,but is true that normally you take the event that 2 cylinders next to each other having a failure remote ,but is still possible ,its what makes making diagnoses sometimes difficult as you rely on correct info ,i suppose you use a big hammer and swear

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Ah you know me so well

If you are not getting mayo and your compression is OK, it could be something as simple as the valve stem oil seals allowing the exhaust gasses to pass through the head, which will lead to your excess smoke coming from the oil filler cap.

They are a simple job to replace ... once you have taken the head off, that is!!

Enjoy!!

You can replace the stem seals without taking off the head in theory.
The idea is to remove the plugs, stuff a load of soft rope in the bores to stop the valve dropping in. Then leaver the valve spring down and remove the collet. Remove the spring and replace the seal. Then replace the lot back to how it was. Don't forget to remove the rope though. Takes ages to pull through the exhaust
I have never done this so not sure if it works but seems logic. Seen it done on other motors though.
Taking off the head is not a too big job anyhow providing none of the bolts sheer.

Re - chucking out oil. Are any of the breathers blocked? Also check that the engine has not been over filled with oil. I know it sounds dumb but its worth checking before removing the head or getting out the soft rope.

Cheers, have not needed to do compression test, as frankly on removing the cap, it is reminiscent of a steam train, chuffing out smoke! And accompanied by the sound of something rattling, I presume is one of the pistons, I have decided to replace head, or whatever I find wrong, by getting a spare cheap engine, (found an ex mod 2.25) fairly locally to pick up) and swap bits I need from it. Here goes the slippery slope of keeping spares, for everything! Ha.

if the spare engine is a good runner I'd be dropping that in as a direct replacement, quicker than breaking both engines trying to keep your current one going

then you'll be able to rebuild the current one at your leisure