968s sucking oil into engine somehow???

[piersman]

So I fitted another new AOS yesterday. Not had a chance to try it out yet though.

Points to ponder, AOS's are a LOT easier to change out the second time once you know how to do it! About an hour.

I cut the old one up to see what's inside and to try and understand how it works.

First off I cut round the top circular section to reveal the diaphragm, it was perfect with no holes. Then I cut straight through the bottom of the main body to see what was in the separator vessel. Not much is the answer, a baffle at the top mainly.

I assume that air is effectively sucked through the AOS from the top connector using the vacuum pressure of the inlet. The air is sucked in from the side connector and the bellows connector. Whatever is picked up in those gets mixed in the side chamber before being sucked into the top of the separator vessel section, hitting the baffle on the way in to allow oil to drip down, and whatever is left to be sucked into the top the AOS where the diaphragm is.

I'm confused a little by the diaphragm. It is spring loaded and I assume that the higher the vacuum (e.g. revs) the more the diaphragm gets pulled against the springs. This seem to be pulling a plunger in the center of the diaphragm towards sealing off the supply to the pipe applying the vacuum pressure. I suppose it could be a rudimentary pressure/vacuum regulator - the higher the vacuum, the smaller the gap for the vacuum to be applied and hence less vacuum pressure.

So for AOSs where the diaphragm has holes I can see that it may not be able to regulate the suction effect and oil mist could be sucked passed the plunger if it's not fully engaged when it should be.

But not sure how it's doing what it does on mine unless the mechanism is jamming somewhere and not allowing the plunger to deploy to it's fullest extent. Then at high revs / high vacuum pressure it just sucks everything out the separator vessel before it's had time to drip back down into the engine.

Anyways, let's see how it goes the next time I get a chance to give it some, I'm not expecting miracles!

On a more positive note, I did get my air con sorted, two new condensors - but all that's highlighted is that one of my fans is not working at low speed. Replacement fan and resistor on order to fix that!

I do wish people would fix things on their cars as they go along rather than just passing them all on to the next mug to sort out, e.g. me!

[kiyakubuke]

Originally Posted by piersman

So I fitted another new AOS yesterday. Not had a chance to try it out yet though.

Points to ponder, AOS's are a LOT easier to change out the second time once you know how to do it! About an hour.

I cut the old one up to see what's inside and to try and understand how it works.

First off I cut round the top circular section to reveal the diaphragm, it was perfect with no holes. Then I cut straight through the bottom of the main body to see what was in the separator vessel. Not much is the answer, a baffle at the top mainly.

I assume that air is effectively sucked through the AOS from the top connector using the vacuum pressure of the inlet. The air is sucked in from the side connector and the bellows connector. Whatever is picked up in those gets mixed in the side chamber before being sucked into the top of the separator vessel section, hitting the baffle on the way in to allow oil to drip down, and whatever is left to be sucked into the top the AOS where the diaphragm is.

I'm confused a little by the diaphragm. It is spring loaded and I assume that the higher the vacuum (e.g. revs) the more the diaphragm gets pulled against the springs. This seem to be pulling a plunger in the center of the diaphragm towards sealing off the supply to the pipe applying the vacuum pressure. I suppose it could be a rudimentary pressure/vacuum regulator - the higher the vacuum, the smaller the gap for the vacuum to be applied and hence less vacuum pressure.

So for AOSs where the diaphragm has holes I can see that it may not be able to regulate the suction effect and oil mist could be sucked passed the plunger if it's not fully engaged when it should be.

But not sure how it's doing what it does on mine unless the mechanism is jamming somewhere and not allowing the plunger to deploy to it's fullest extent. Then at high revs / high vacuum pressure it just sucks everything out the separator vessel before it's had time to drip back down into the engine.

Anyways, let's see how it goes the next time I get a chance to give it some, I'm not expecting miracles!

On a more positive note, I did get my air con sorted, two new condensors - but all that's highlighted is that one of my fans is not working at low speed. Replacement fan and resistor on order to fix that!

I do wish people would fix things on their cars as they go along rather than just passing them all on to the next mug to sort out, e.g. me!

my observations on the AOS are similar. one theory I have is that the spring gets worn out over time and doesn't "spring" properly anymore. when mine went out it seem to get progressively worse rather than just "good one moment, broken the next"

[piersman]

As an update...

So, I persevere with the Boxster. I spent £600 getting the aircon sorted, a new hood with glass window and a new key switch. Car's looking good and driving great.

So about 4 weeks ago I used it for work 3 days in row. Then got a check oil level warning.

I checked the oil and noticed it was about a litre down, strange, no great sign of any oil loss or oil burning off. I then checked my water level. Oh oh, not good, nothing but emulsified oil in sight. So I drained out the coolant and reckon 25% of the 15 litres or so I extracted is enulsified oil. At least I know where my oil has gone. :laugh:

So, a heat exchanger or cracked cylinder head. The heat exchanger is only a year old so someone has been this route before and dumped the car as a PX. I'm the lucky mug that then picked it up.

The car has been into the garage today , they've stripped out the engine and confirmed that CH 4-6 is fecked and has been allowing oil into coolant and most probably over pressuring the cam covers causing the AOS issues I started this thread about.

A big decision to strip out the engine, it's a very fine line between whether to scrap the car or repair it as the cost of the engine work will likely be about £2.5K using a second hand replacement head. Only the fact that I've invested so much time and money into making the rest of the car so good persuaded me to go ahead and repair.

Bloody Boxster!!! Can;t wait to get it back for what's left of the summer though!