Smokey Exhaust

[Sussex Pete]

Being concious of the new MOT regulations and the #436 will be due in September, I thinks its time to acknowledge that its engine is a tad more smokey than I was expecting. So far, since the rebuild, its covered 350 miles. The old problem of hesitating and behaving as though there is fuel starvation is still there, but thankfully only on the odd trip and its seems to be after a short stop, such as filling with fuel. More worryingly is that there is blue smoke from the exhaust almost all the time, worse on overrun with a hot engine, yet I'm not losing oil. My thoughts about what may be wrong include:
1. Turbo - this was overhauled with new seals and bearings as part of the rebuild. I shall be exremely peeved if it is this!
2. Valve stem oil seals - not replaced as nothing suitable available.
3. Crankcase ventilation breather pipe - fitted the restrictor in the inlet manifold adapter, but not sure if the regulator valve is working as it should.

Any of you guys got any thoughts on where I should focus my attention both before the MOT and then during the winter layup?

[Doctordiesel77]

Are the valve stem oil seals not just a standard imperial size?

[Sussex Pete]

Are the valve stem oil seals not just a standard imperial size?

The simple answer, John, is I don't know. The turbo engine is different in that there are oil seals on both inlet and exhaust. On the other O series engines they are just on the inlet. As such I don't know what the difference between the two seals is, as the exhaust version is an NLA item. Is it size, material, shape or a combination? I'm sure that I have also read somewhere that there was a possible substitute, but naturally I couldn't find that info when I was rebuilding the engine, so had to take a punt that the existing seals would be OK.

[Doctordiesel77]

I'll try to find out..I know the exhaust is bigger on the turbo, but not sure if material is any different. Sean Turnbull on the facebook group might have some, worth asking anyway.

[Sussex Pete]

Update on this situation. Valve stem seals for exhaust valves can be acquired. They are fitted to a Mercedes engine. PM me if you need to part number. Mine have now been changed and an initial road test appeared to confirm that the exhaust smoke on overrun had been fixed. However, after a few more runs, it returned to the same level as before, so I now suspected the turbo rebuild was not as good as I hoped it had been. Thankfully I have been able to purchase a NOS T3 turbo and after the swap over, I can see that the old one had been leaking oil qute badly. Professional rebuild is now planned for that one. Only issue now is that the engine dies under load as soon as the turbo starts to spool up. Suspect the mixture at the moment, in that it was probably previously set to compensate for other issues found during the turbo swap, but will also be checking pipes for leaks, etc.

[ian drew]

Hi Pete. Good work on finding the smoke, one of those tasks that can go on forever.
My only suggestion on the cutting out when about to go on to boost would be the pipe that takes pressurised air in to the carb thus increasing the fuel flow to compensate for the extra air. Off the top of my head I think it's the pipe right at the front of the carb on the top, even a TINY split causes issues. Can be replaced with a short length of fuel hose.
Good luck,
Ian

[Sussex Pete]

After two days of head scratching, finally got the solution this afternoon. It was the anti run-on valve all the time. Even though the solenoid inside was operating it wasn't closing the valve completely. Standard fix of sealing the pipe with a bolt and understanding the potential hot start issues is a small price to pay.

[ian drew]

Nice one. My car used to smoke (and therefore still will) before I took it off the road. I expected to find play in the turbo shaft but there isn't any, maybe this is what was causing mine as well!
Ian

[Sussex Pete]

Don't want to put a dampner on things but my smokey exhaust was a failure on my turbo rebuild. Peeing oil out of the exhaust housing and turbine blades absolutely black was an indication of the problem. May have also been compounded by not changing the exhaust valve stem seals during the original rebuild - they are NLA as a BL item, but found some replacements that fit perfectly.