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Discussion Starter #22
So no need to take it back to Meineke?


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the lead mechanic there works only when he has time, so not for now.
I have oil leaking from differential now:
I think the loose drive shaft stressed out the seal, causing this leak. Just disappointed in the quality of work done by others.
Going to bmw dealers will be a different kind of rip off.
I stopped going to another BMW "expert" after he messed up my 1995 850ci. I have to do most things myself to make sure work is done correctly.
 

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I have to do most things myself to make sure work is done correctly.
Regarding your leaking diff, seems like you have a leaking input shaft/pinon seal. That's not exactly an easy job, unless you've worked on differentials before. You might also do the output shaft seals too. Alot of mechanics don't have much experience with differential rebuilds. You may consider going to someone who does 4x4 and truck differentials, they will do it right. There is nothing special about the M5 differential.
 

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the lead mechanic there works only when he has time, so not for now.
I have oil leaking from differential now:
I think the loose drive shaft stressed out the seal, causing this leak. Just disappointed in the quality of work done by others.
Going to bmw dealers will be a different kind of rip off.
I stopped going to another BMW "expert" after he messed up my 1995 850ci. I have to do most things myself to make sure work is done correctly.
I totally understand that...I also do all the work myself.


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Discussion Starter #27
That's a good improvement. I'm assuming you were never able to get to the other two?
Correct.
Its a $25 maintenance part and shouldn't be more than an oil change effort.
i will give it another shot, maybe go ask bmw technicians how to replace it.
 

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Discussion Starter #29
Do replacing these bad pcv valves help with MPG at all?
There may be microscopic improvements, but hard to judge. I never say any noticeable change in mpg.

The valves should be closed during higher RPMs. The spring is designed to open up only during idle rpm when crankcase pressure exceeds more than the intake manifold. At higher RPMs, intake manifold has higher pressure so effectively sealing off the intakes providing better combustion. Also, at higher RPMs, there is more oil sloshing around and that should not get into the intakes with bad PCV Valves.
 

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I'm trying to understand this. The ffg article says pcv valves should be open at high engine load/high rpm, and should be closed at idle.

I'm not sure how accurate the article is, because it seems to contradict op's take on how the system works on our cars?
 

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Discussion Starter #32
I'm trying to understand this. The ffg article says pcv valves should be open at high engine load/high rpm, and should be closed at idle.

I'm not sure how accurate the article is, because it seems to contradict op's take on how the system works on our cars?
it opens and closes based on pressure difference. Crankcase pressure increases more than manifold - it opens.
At idle - manifold has high vacuum. so it should open up. its also the best time to burn up crank case gases when engine performance is not a criteria.
 

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All this valves are check valves. They flush the oil back to the pan from the cyclone separators and condensation from the plenum itself, when the engine is off. Only place that ventilation of the crankcase is done are hoses which are on the top back end of the cylinder head covers. All 4 plastic hoses which have those valves are to bring back oil to the pan via openings going all the way thru the cylinder head, engine block, bed plate and pan.
I guess the explanation why you have better oil consumption is because oil is drain back down, instead burning it into the cylinders.
Did you try to blow/suck the old valves, do they pass air?
 

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Discussion Starter #34
Did you try to blow/suck the old valves, do they pass air?
Never tried to do that. Will test. the Driver side top valve was leaking oil. Its hose going into the manifold was super wet and oily while the passenger side was dry and clean. Replacing it has drastically cut down oil consumption.
 

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Never tried to do that. Will test.
Cool, would be interesting to check.
But saying that hoses were oily, makes perfect sense that valves are stuck closed, so oil can not flush down but instead dripping at the connection ,thus engine burns this residue oil, cause it stays in the plenum.
 

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Discussion Starter #36
if valves are stuck closed, how is oil coming up ? I fail to understand your explanation. I thought the one faulty valve was stuck OPEN so oil droplets in crankcase air were getting sucked all the time from the crankcase.

This is interesting: When level is at +1.0, the oil was getting consumed at the rate of 0.1 every 100 miles.
So, in 500 miles exactly, level was dropping to +0.5.
From there, it was super high. In the next 150 miles, the remaining 0.5 quart was used up.
SO, my car was burning up 1.0 quart in 650 miles. Happening for nearly 6-8 months.

After fixing just one PCV valve, that was having wet hose at the top, its now used up 0.2 quarts in over 500 miles.
(BTW, car is in pieces in the garage now, trying to replace exhaust manifold with used ones on ebay with cats. Mine didn't have cats and I want to have cats).
 

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it is very interesting indeed.
I was think that if the valves are stuck CLOSED, oil which was separated by the cyclone separator fitted in the plenums , was not draining back to the crankcase. Now that you are saying you had a huge consumption in the begging when your oil was full up top, it sounds that they could be stuck OPEN, and thus oil sucked up in the plenum. You can see where are all those passages goes from the PCV valves. That would explain it well. But even more interesting is why when the level oil was 0.5 less, it was actually burning even more?! I can not imagine the answer of this question now.
s-l1600 (1).jpg
 

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Discussion Starter #38
My only explanation is, when oil level falls low, it was creating more sloshing effect in the crankcase and more oil droplets in the air that was getting sucked up quickly.
 

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I replaced all four of these today. It wasn't too bad.. a little swearing and sliced up fingers, but ok.

The two above the bell housing were a bit of a PITA because getting a socket drive in there with a bit was pretty much impossible. I used a T30 socket and wrenched on it with a 6 mm open end wrench. You also need to unsnap the vent hoses from their holders behind the intake plenum so they can be pushed up off the valves.

All four were a PITA to pull out, but the ones above the bell housing were a little easier because you can get a screwdriver on them to pry them out. Before installing, I liberally greased all the o ring connections to make sure they come out easier next time.

Driver side

935208



Passenger side

935210

935211



Vent hoses behind plenum

935212



Hose holders

935213



Two valves above bell housing

935214

935215
 
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