heliflyer

Dave - thanks for your help - it's 3 am here at the moment so will post some pics in the morning.

Ptuomov - for the record, I dont use pirated software. I asked for Dave's advice because he designed the layout of the system and will no doubt know what he is talking about and have the best idea as what might be wrong.

Michael - I agree absolutely - and very much appreciate the support from the 928 gurus here on the forum rather than the plethora of folks who seem to sit here waiting to post snide comments rather than help.

Glen - Not a lot of smoke, but certainly visible under acceleration.

To all those who have asked relevant questions and provided suggestions - Thank you.

GlenL

This is all sounding unfortunately familiar. (Besides un-helpful chattering)

A few years back I was busy trying to control smoke from my engine when driving at the track. Some smoke on the street, too. Turned out to be broken piston rings and piston lands. (The bits on the piston between the rings). The compression numbers weren't bad. Still give that a compression check and look at the spark plugs for un-even color.

Lizard928

Glen has it correct....

chewy8000

DFiXid you do the headgasket work or did someone else? If you didn't do the work do you trust someone did a compression test at some point? Shouldn't be blowing smoke after a headgasket change. If it started soon after I doubt it's the provent.

heliflyer

Glen & Tristan - thanks for the suggestions.
I did the gasket change myself - slight signs of smoke have been visible for a while, it is not a new thing since the gasket job or the provent addition.
The engine does however run really nicely - no funny noises - plenty of power and good and smooth.

Dave - pictures of the install below - one thought came to mind in the early hours - when I did the drive that resulted in the oil ejection, I had not yet fitted the air filter to the outlet port on the provent - is it possible that the airflow from driving / fan blowing across the opening might have created a venturi effect causing oil to be sucked up through the cam cover pipe into the provent? clutching at straws possibly, but other than broken rings causing the crankcase to be massively over pressured I cant think of another cause.

IcemanG17

very odd

something must be seriously wrong to get that much oil in only 8 miles......on my estate racer I capped everything and the only vent is a K&N filter at the top of the filter.....I run high rpm under race conditions and the filter barely gets damp? Something must be blocked....

Ed MD

In my Euro the non-return valve is horizontal and occasionally stuck shut because of oil that hadn't drained out of the valve thus causing a blow by from the top part of the Provent. Dave recommended repositioning the non-return valve to an upright/vertical position . I thought I could get away without using it. Big Mistake! Normally this is a closed system, but with the Provent it is vented to atmosphere via the small K&N filter. Without the check valve, the crankcase is pressurized enough to send the oil up to the Provent and sprayed it vigorously through the K&N filter. After I cleaned up the oil and replaced the valve, vertically now, I also replace about 1/2 quart of oil that was vented. Needless to say you duplicated my experience.
I truly appreciate all the thought that Dave gave to his design.
Ed M

heliflyer

Ed - Thanks for that insight - it does sound as though that is exactly what has happened. I have not yet fitted the return line to the sump as I cannot source the check valve yet so my current system is, as you describe a completely open system.
My concern at the moment is that even after the drain line and check valve is installed, that will effectively be the same set up at present with the plugged drain port (other than the fact that a flow of oil through the provent could drain back to the sump) so I would think I will still have the current problem.
I too appreciate the thought and effort that went into Dave's design which is why I especially asked for his comments on my problem.

Ed MD

From my experience, it seems that the top portion of the Provent is essentially a "low pressure sytem", where the internal "screen" captures the oil and the air, sans oil vapor, is vented via the K&N filter, and the oil collects in the bottom of the Provent "reservoir". The bottom half is a "high pressure system" that is checked from back flow up to the Provent by the non-return valve. Neither "ends" are under constant pressure. When the crankcase isn't pressurized the oil flows down out of the Provent through the check valve and back to the crankcase. The problem I had with a horizontal valve was the any oil that had settled and not drained because of the horizontal position kept the valve shut by hdroscopic pressure. So far, the vertical repositioning of the valve appears to work fine. Best of luck. Ed M

Imo000

You have way too much blow by to get that much oil in such a short time. Do you have the proper oil level dipstick in your engine? Maybe it's over filled.

smiffypr

The hose which comes from the block to the side of the oil filler, is that squashed or kinked?
Is the gauze basket inside the oil filler still there?

heliflyer

Imre - dipstick is the correct one and oil level confoirmed by the initial qty added after the head gasket change, but thanks for the thought.
Smiffy - checked both of those - hose is fine and gauze basket still there and is nice and clean - ie not blocked.

Glen - thanks for the thoughts even though they are not positive ones!!! Unfortunately I have to say that I tend to agree with you as I can't logically think of any other reasons for the smoke. I'll pull the plugs and do a compression test tomorrow - unfortunately all my tools are away from home at the moment so can't do too much more today.

I have subsequently removed the provent system and run the car again in it's factory configuration and there doesn't seem to be any evidence of high crankcase pressure anywhere - ie oil is not being forced out of a loosely fitted oil filler cap.
I am beginning to think that my problem was running the provent system without the small K&N filter fitted and that the combined airflow from the rad fan and from driving at high speed has created a venturi effect that has sucked oil from the cam cover breather hose.

I have another issue now unfortunately - it looks as though the other cam cover gasket, although new, has let go as I had a massive oil leak down that side of the engine when running it today.
Needless to say, I'm a bit fed up with it at the moment so have ditched it in the yard and will get under it with a torch tomorrow when I'm in a better frame of mind and try and confirm the location of the new oil leak.

Thanks for the suggestions guys.

Alan

Sorry for your troubles - but I think you are indeed grasping at straws now...

Certainly its not a venturi effect from the outlet..

There should never be that much flow of oil through the provent - it probably wouldn't reliably drain fast enough to handle it anyway. Something is seriously wrong elsewhere... Clearly there must be excess crankcase pressure for this to happen - diagnose that (check compression, evaluate oil loss rate with stock set-up

Alan

James Bailey

This does not translate well..."I'm a bit fed up with it at the moment so have ditched it in the yard and will get under it with a torch tomorrow when I'm in a better frame of mind and try and confirm the location of the new oil leak." In the US "torch" has a far different meaning..

heliflyer

Sorry James - should have said flashlight !!!

Alan - I agree - The strange thing is that there doesn't seem to be a problem with the stock set up other than the blue smoke under acceleration which, in conjunction with Glen's comments has me concerned for the piston rings. Since the head gasket change the car has run 1500 trouble free miles until this sudden spate of oil leak issues, but I have had to add maybe 2.5 litres of oil in top ups.

Does anyone know of a means of measuring the actual crankcase pressure and if so what the values should be?
I am thinking that I should just pull the engine again and rebuild the bottom end.