These two hoses in the back lead to a non return valve - but should we replace these also, where do they come from - are they breather valves from the gas tank canister.

 

The crankcase valve is replaced on the bank2.

 

This hose end had significant oil on it. I believe this part should be dry.

 

Im interested to know as well, I man seeing about 1/2 quart burnt for every ~500 miles too.


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I have changed the 2 at the top.
The 2 at the bottom behind the engine - no idea how I am going to get to them.

 

You can always remove the SMG [emoji16]


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Have you seen an improvement with oil consumption with the upper ones replaced? It might be best to wait until the next time you have to service the SMG to replace the lower ones.


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there must be a simple way to get to them, they are $20 part, maintenance items.
Anyway, i have asked EcsTuning also, if they can comment how to replace.
I will write to BMW,didn't we have a shop manual before for some of our cars ?

 

Good point.

From the upper two, the driver side had oil traces, but passenger side was bone dry.

From the lower two, that go into tue back side of each intake manifold, both show oil on the inside of the hoses. I will run the car for few weeks and report back.

Historically, car hasn't seen tarmac for 4-5 months. I started replacing the TAs after new flywheel and clutch was installed, and got stuck with TA work and couldn't get into it till now.

I took the cwr for spin and its drive shaft started shaking, some bolts were not tightened from earlier clutch work sadly.

Now, i see oil dripping from differential- drive shaft seal only when rear wheels go up on a ramp.

Am gonna drive it around and see if oil is getting sprayed a lot. Its just a non stop list of issues lol. I may have to get the seal fixed before any serious driving with this.

 

Good point.

From the upper two, the driver side had oil traces, but passenger side was bone dry.

Historically, car hasn't seen tarmac for 4-5 months. I started replacing the TAs after new flywheel and clutch was installed, and got stuck with TA work and couldn't get into it till now.

I took the cwr for spin and its drive shaft started shaking, some bolts were not tightened from earlier clutch work sadly.

So you were saying you replaced the driver and passenger oil return hoses? The driver side you mentioned was leaking. On mine the driver side is a little wet with oil will be addressing that after my family vacation. Haven't noticed anything on the passenger side. But the oil consumption is normal I guess, around 1 quart per 1k miles or so.. unless I punch it hard a lot like lately it will be around 800 it will start asking. And that little hose is 56 bucks at ECS.

Also, can you get away with not removing the plenum installing those oil return hoses?

 

I broke one of the lower ones, and had to lower the motor(when I was doing r/b) to get to the bolts that holds them in place. Once the retainer is unbolted the hose uses the same push release clips to remove upper half of hose from plenum. I was unable to get to the lower half since it goes above trans. So I wouldn’t mess with them.

 

UPDATE: Drove the car about 180 miles now, and the oil is still at +1.0 very happy with this. Car was burning 0.1 every 100 miles till 500 miles, and then the rest 0.5 in about 150 miles.

So, i just replaced the 2 PCV valves just behind the intake manifolds. Driver side PCV valve hose that goes into intake was very oily, dripping wet, and its clean now. I don't see any sign of oil.

I am still debating how to replace the two above the flywheel all the way in the back. Will go ask BMW how to do this.

 

Update: Oil level now reads +0.9 after 260 miles So happy.
So, it has used 0.1 Q in 260 miles. Thats darn good.

 

You take the hose off at the intake manifold and check if it has oil at the top. Don't change the PCV valves needlessly.
They are like $20. Got them from ECSTuning.
One important thing I have realized, always buy genuine BMW parts. They have the perfect fit.

Positive Crankcase Ventilation (PCV) Valve

Clear codes & keep your emissions system working properly

www.ecstuning.com

I got 4 of these, and have 2 left still.

 

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:

2008 m5 Driveline vibrations, loud clunking noise only...

Finished working on TAs (https://www.m5board.com/threads/2008-m5-135k-bank2-throttle-actuator.606764/) and got the car running smooth, and next morning, i see heavy vibrations , and a distinct clunking sound only while accelerating. Car runs smooth while going down hill, no sound. Car revs super...

www.m5board.com

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.

 

UPDATE: car has clocked 439 miles and oil level at +0.8

 

That's a good improvement. I'm assuming you were never able to get to the other two?

 

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.

 

At high rpm there is blowby increasing crankcase pressure.

 

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.

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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?

 

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.

Redirect Notice

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.

 

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?

 

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.

 

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).

 

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.

 

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.

 

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

Passenger side

Vent hoses behind plenum

Hose holders

Two valves above bell housing

 

...I used a T30 socket and wrenched on it with a 6 mm open end wrench...

View attachment 935215

OMG , You are my god for today !! ???
I had no idea how to get to them. Was gonna just drill a large 1 foot hole into my dash.

 

Do you guys have actual pics of these valves you removed/installed. Just a little curious..

 

Update:
I clocked about 900 miles with my Oil indicator at +1.1L.

It used to be +1.2L after I put the car back together after replacing the exhaust headers, and I reset the odometer once it hit +1.1L. After 900 miles, it dropped to +1.0L. I drove another 26 miles and it dropped to +0.9L immediately. very strange, but still acceptable. After another 80 miles, its still at+0.9L.

I have been riding the car pretty hard at times, glad to have it all back together. It was unused for nearly 6 months when I was replacing the exhaust headers with OEM with catalytic converter.

 

Interesting thread. Just one small item to consider on the pcv operation. Remember pcv stands for positive crankcase ventilation. You mentioned earlier about vacuum in the crankcase drawing the oil/vapor from the intake manifold but the crankcase is not likely ever drawing a vacuum (maybe when the engine gets shut off). The crankcase is pressurized primarily by some of the combustion gasses getting past the piston rings. The intake draws a vacuum but on an ITB setup we don’t have that large plenum chamber post throttle which has a large volume of air.

So it seems there are valves to drain excess oil back to sump but generally PCV valves are just to vent crankcase pressure (nasty oily, fuely vapor) into the intake so it can get burned up in combustion. One of the benefits of dry sump systems is the ability to draw a light vacuum in the crank case which reduces parasitic power loss.

 

Update on this:
After PCV Replacement, i drove the car for 900 miles, with level at +1.1L on the dash.
After 900 miles, it drops to +1.0L.
In another 26 miles, it drops to +0.9L. I keep driving it, and it was at +0.8L for a while, for nearly 450 miles.
SO, i have covered about 1350 miles now with a 0.3L consumption of oil, apparently.
Yesterday, it recomputed again while driving and the level drops to +0.2L !!! What the Heck. Straight from 0.8 to 0.2. This is very disappointing, depressing, and has demolished my confidence in this car. The (un)reliability of this car is beyond belief.

How do I know on next reading in another few tens of files it won't drop down to negative 1L ?

I was thinking the consumption and oil level drop will be linear with miles.

 

Update on this:
After PCV Replacement, i drove the car for 900 miles, with level at +1.1L on the dash.
After 900 miles, it drops to +1.0L.
In another 26 miles, it drops to +0.9L. I keep driving it, and it was at +0.8L for a while, for nearly 450 miles.
SO, i have covered about 1350 miles now with a 0.3L consumption of oil, apparently.
Yesterday, it recomputed again while driving and the level drops to +0.2L !!! What the Heck. Straight from 0.8 to 0.2. This is very disappointing, depressing, and has demolished my confidence in this car. The (un)reliability of this car is beyond belief.

How do I know on next reading in another few tens of files it won't drop down to negative 1L ?

I was thinking the consumption and oil level drop will be linear with miles.

I've experienced the same and even thought my brand new oil level sensor was playing tricks on me that at one point I was having doubts with the reading. Just recently, mine was at 1.0 then all of a sudden dropped to +1 quart at 750 - 800miles since last top off. Could be that I rev high a lot and also maybe cuz Im running Redline 5W50. Car runs great even after I had a misfire scare with burnt out #2 and #10 plug. Gonna go back to Castrol 10w60 and see what happens.