View Single Post
      07-11-2012, 04:05 AM   #46
335i E92
Captain
20
Rep
686
Posts

 
Drives: 335i E92 SE
Join Date: Mar 2010
Location: Manchester

iTrader: (1)

Quote:
Originally Posted by doughboy View Post
H, missed this thread!

Compression test will prove rings, valve seats and head gasket. It would be a good start and is easy to do for a garage.

Leaks leading to unburned oil or fuel in the exhaust will destroy your CATs and your O2 sensors if not sorted.

Any startup problems with the HPFP will just lead to excess cranking as the ECU won't open any injectors or fire any ignition until fuel is up to pressure and ready to go. So it may give more cold 'cranks' for oil to be drawn in from any leak before firing thus giving a larger 'puff', if that makes sense?

I agree, when cold, oil in the turbos would't 'puff' blue smoke on start up. It needs to be oil in the combustion chamber for that to happen.

When not running, so you get a start up 'puff', excess oil can only get in the combustion chamber in 3 'gravity assisted' ways:

a) leaking head gasket between oilway and combustion chamber
b) leaking valve stem seal allowing oil to run down a stem from the cam chamber above (past open valve, or pooling on a shut one)
c) oil in inlet manifold running in past open inlet valves, or pooling behind shut valves and being drawn in on start up.

If its a) then this works both ways and will pressurise the oilways/crankcase with combustion gases when running, exacerbating any problems with the PCV, or it will suck oil in to the chamber when on overrun (throttle closed). Has anyone followed you to see if it smokes constantly on overrun, or gives a big puff when you get back on the throttle after overrun?, I suspect it will, as to lose as much oil as you are it can't just be start ups. I also think it will not smoke under acceleration.

If its b) then again it will also smoke on overrun or when re-applying throttle.

If its c) unlikely as you've change the cam cover and integrated PCV cyclonic filters.


BTW mine never uses any oil ever. It's never gone down from 'full' between any oil change (6-8K changes, so i've never put any top-up in it in 40K.

Mike, thanks for the detailed input!!

Firstly, i can rule out any fuel related issues including the HPFP as it starts instanly on the button, iíve also had all injectors inpected and changed within the last 8 months. (All injectors are the latest 9th edition part numbers) Second to that the plugs weíre inspected at the wíend and all looked healthy, no carbon build up etc

Point a) Its definatley not a head gasket issue as it was replaced when they did the head, I donít use any coolant and donít get any hot oil smell when up to temp to suggest and external leaking head gasket.

Point c) As you say, unlikley as I had the whole cvankcase cover which contains the PCV check valves replaced recently.

This can only leave one possibility and thats the valve stem seals!! Having spent £1000ís on the head re-build i just canít accept this as somthing iím happy to live with. Iím going to have to speak to Woodís and have the uncomfortable conversation of how we rectifiy the situ, hopfully they can do some tests (compression or whatever) to confirm what is at fault and then we can look athow much of a job it is to correct.

If it is the seals, does anyone know how big a job this is? Are we talking similar to a head gasket change engine out kinda job or smaller?