tveltman

Some of you may remember my oil burning difficulties that began about 800 miles ago. I was having a lot of trouble isolating the problem. Since then, I have installed a sharkvent kit, but this did not fix the problem. My assumption was obviously that the oil was simply being ingested through the PCV system, however it would appear that this is not the case. Finals are at last over, so I don't have to teach again until the beginning of January, so today I went out and pulled the intake manifold/throttle body. I pulled the side covers off of the manifold and cleaned the inside wherever I found oil residue/dirt/whatever. I then inspected the throttle body and found a puddle of oil in the well at the bottom, which I cleaned up. I also carefully looked inside, and it appears that there is oil leaking in from the port where the Y hose fits (this hose goes between the intake, the oil filler neck, and some sort of solenoid). The air pump has been off this car for ages, as it was rock solid when I got the car (no belt from PO i suppose). It would appear that that hose only travels between the oil filler neck, the intake, and the air pump diverter valve, passing through a solenoid. Is there any reason not to simply plug the filler neck port and the intake port and remove this hose entirely? Is there an alternative way to route this to bypass the intake? I will confess my utter ignorance where it comes to this portion of the car. I have a set of newer-generation cats (which don't require an air pump) waiting to be installed, but obviously I see no reason to blow oil smoke through them when I can fix the problem and start fresh. At this point I have the intake and throttle body all cleaned and reassembled, to be put back on tomorrow.

It seems that porsche's intention was to take the PCV vapor and route it either through the intake or through the air pump into the cats to be combusted. Is it possible that this is what is causing my problem? Could the solenoid have failed somehow, resulting in a sudden surge in oil consumption? For reference, the part number on the unit is 0 200 142 151, made by Bosch. I only found one reference to it in the archives, and that was in Dwayne's most excellent intake R&R thread, where he called it the "fuel vent solenoid", and even that was only in reference to the Y-hose, not the item itself.

As a reminder, all 8 plugs are blackened, so I doubt it is anything but an oil-in-intake problem (i.e. not rings or valves), and this problem came on relatively suddenly. I checked over all the vacuum connections, and I couldn't find a single hose misrouted. Bill Ball has graciously offered to come take a look at the car in a few weeks, but if I can remedy the situation without bothering him, that would be nice.

Thanks again!

Mrmerlin

928 international makes a block off plate to contain oil that gets flung up to the bottom of the filler spout, since you have the intake off now is the time to put one on to find this part type in oil control on their search function

tveltman

excellent call! I didn't know they made such a thing, but I will call them first thing tomorrow morning

heinrich

I believe the only reason for this type of oil burning / ingestion via the breathers, is a failing head gasket or valve seals.

Alan

The oil is coming from the oil filler connection and bypassing the sharkvent - that filler connection should no longer be there (capped)...

This is still a PCV system issue (...you have oil in the intake...)

Alan

Mrmerlin

Alan can you be more specific about capping off the spout??
I put one of the block off plates into my 1988 and will see if it reduces the oil burn/ingestion.
From what I can see this plate is a shield to the crankshaft and blocks off the oil thats slung from the crank to the bottom of the filler tube housing, in the hope that it will reduce or eliminate the oil transfer into the intake

Tom in Austin

Speaking of the 928 Intl block off plate, does this work ok with the newer plastic filler units? Does your '88 have the plastic type Stan? If so, where did you put gasket(s) and/or sealant?

I believe there's an O-ring type seal (though not shaped in an 'O') you use on the plastic type but not sure I ever heard if this on top of the block off plate completely seals it up or maybe you put something between the block-off plate and the opening?

Mrmerlin

I used a new filler tube since mine was leaking, ( they do warp from the heat)
With a new O ring and I also used Hondabond to seal the filler tube/O ring to the block off plate and to the block .
The plate did require a bit of dremeling to fit properly but beyond that it seems to have sealed up well

Alan

yes it works fine with the plastic filler necks. You use the standard old style <87 gasket underneath the plate (+RTV/similar) and the o-ring on the top (use a new one) works & seals fine.

All the oil filler neck ports need to go to the sharkent or be capped so nothing goes into the intake - else oil in suspension will still make it around the plate and back into the intake. Particularly if you have excessive blowby driving it "up the spout". The port to the Y should be capped off inside the neck with a slip on cover DR provides...

Alan

tveltman

Ahh, I must have missed that page in the instructions. It will be remedied tomorrow hopefully then.

tveltman

I put the plate in and capped the port on the throttle body and oil filler neck today. I started up the car and let her idle for a little bit, then popped open the filler neck and found it was bone dry, so no oil is escaping up into the neck as it was previously. The car seems to be idling as usual. Under about 2900 RPM, the exhaust is clean, but over that magic line, it starts pumping out oil smoke. Once I lay off the throttle, the exhaust returns to its previous clean state within a minute or less. This happens regardless of the engine temperature. I haven't yet checked the plugs or the well in the throttle body (engine still hot), but I expect to find oil residue on all 8 plugs and no oil in the TB. I can clean the plugs off and drive the car for a little while to see if the oil distribution changes any, which might be an indication of a failed ring, etc. I previously posted compression numbers which I thought were not great, but seemed to be okay. At this point, I have two theories, one hokey, one dismal:

1. After all the running with highly oiled exhaust, the cats are thorougly soaked and the high rate of exhaust flow is enabling that oil to slowly burn off of the surface of the cat (hokey)

2. Valvetrain or ring(s) have failed, and I'm screwed (dismal)

Thanks for everyone's help, it really means a lot to me.