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Discussion Starter #1
Hey all,

I've got an "issue" that I've noticed with my M5. When it is started in the cold, especially after not being driven for a few days, I am able to pull a VANOS Low Pressure code right after start.

The car does not throw a code or CEL, this is me monitoring each start with my Peake reader proactively.

Anyways, I'm wondering, has anyone had to - or preventatively - changed their VANOS accumulator, which could be losing pressure (especially in the cold)? Obviously, accumulators over time will bleed down (they even do on advanced aircraft hydraulic systems, which is normal). I am just curious if this happens on all M5's and is normal, or if it is something I should look into (recharge of nitrogen in the accumulator, replace entire unit, etc).

I'd love to hear from Troy Jeup and Jcolley, specifically since I found this reply from Jcolley on the interweb which seems like he had the same issue:

Derailing OP's thread a bit here, but when I first purchased my 2006 with 50k miles about 2 years ago, I had similar problems on the few nights I left the car out of the garage through the winter. On startup, I would receive a CEL and when scanned, a VANOS low pressure code would turn up. However, when performing the VANOS pressure test using either a manual pressure gage or the test routine at the dealership (ISTA/D with the IMIB test box), the pressure would read normal.

The VANOS on the S85 has an accumulator similar to that of the S62. On early production S62s, there was no solenoid valve to hold pressure in when the engine wasn't running, but it was added on later years and I believe could be performed as a recall if a client asked for it. This holds pressure in by shutting when the engine is off and the DME energizes (opens) it as the engine turns over for starting. The accumulator then pressurizes the system and holds pressure until the VANOS pump discharge builds up and maintains pressure.

I always suspected that perhaps in really cold temps, the accumulator valve would leak by a bit and allow pressure to slowly drop. This would trip the code on startup, but then pressure would be fine after running. I never had confirmation for this and never saw it again after switching to 0W-40 oil since I suspect the VANOS pump can ramp up the pressure faster on start.
I know S62's a bit, and the early ones didn't have a VANOS accumulator installed. This lead to VANOS rattle for a few seconds after start, and I do hear this for about 0.5 seconds after a cold start in my E60. I don't think this is a big issue personally, but I'm curious what the Jedi's think (Jcolley, Troy Jeup) :)
 

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i bought a used one when i got the code for the accumulator, mine was actually unplugged when i went to replace, so i have one if you want to buy one. its from an 06 w/ about 50k if i recall correctly. im in 07052 if you want to take a trip or i can send you some pics, let me know.
 

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Discussion Starter #3
i bought a used one when i got the code for the accumulator, mine was actually unplugged when i went to replace, so i have one if you want to buy one. its from an 06 w/ about 50k if i recall correctly. im in 07052 if you want to take a trip or i can send you some pics, let me know.
Interesting. Lets see what the forum thinks, but if I'm in need of a new accumulator I'll let you know. I work out of Teterboro, so meeting you there wouldn't be out of the question if need be.

Thanks,

Steve
 

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I recently got an "increased emission" light on after a cold start.i had the car scanned and threw codes 271A and 275F.a local indy shop told me its the oil pump.i know the codes are coming from bank 1 ONLY and after reading this I'm going to take my M5 to another shop to have them look into the VANOS accumulators.
 

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i bought a used one when i got the code for the accumulator, mine was actually unplugged when i went to replace, so i have one if you want to buy one. its from an 06 w/ about 50k if i recall correctly. im in 07052 if you want to take a trip or i can send you some pics, let me know.
Would you remember the actual codes? What shop did you take your beast to?
 

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the code was DME- 278B: VANOS pressure accumlator valve, activation- Open circuit- Fault currently present. i have the BMW software on my laptop.
 

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This happened to me last year during the winter, cel light came up , I took it to my Indy shop and they checked the pressure and it came up all good. My solenoids were change not to long before. It happened again not to long after that , I pulled the codes myself with my laptop and cleared them, figuring it was related to the cold weather. I don't remember the specific codes but it was related to the vanos pressure. I haven't had a problem since. Hope this helps.
 

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This happened to me last year during the winter, cel light came up , I took it to my Indy shop and they checked the pressure and it came up all good. My solenoids were change not to long before. It happened again not to long after that , I pulled the codes myself with my laptop and cleared them, figuring it was related to the cold weather. I don't remember the specific codes but it was related to the vanos pressure. I haven't had a problem since. Hope this helps.
What shop checked the pressure for you?
 

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Discussion Starter #10
The only VANOS related code I've got pertained to bank 1, and it was 27b6, VANOS pressure low. Only happens after start, and does not cause any CFL or increased emissions or reduced power. I'm wondering honestly if it is a normal condition, since there are no CELs for the driver to be notified. Kind of like in conventional cars, when you start up and the engine oil pressure light extinguishes as pressure builds. It's interesting that there are failure codes for a bad valve and an unplugged unit. I can rule those issues out. It just seems like the bleed happens quickly, but I dont know what is normal in these cars yet. Can accumulators be serviced? I'm assuming on the other side of the piston is nitrogen... Anyone?
 

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I believe this is a bladder type accumulator, but haven't opened one up. There is a N2 precharge, but no test procedure in ISTA/DIS like there is for the SMG accumulator since it's not a controllable pressurization source.

I would have a shop perform the pressure test first and go from there. Replacing the accumulator is cheap and easy (relatively speaking), but irrelevant if the pressure is low. Possible causes of low pressure could be solenoids failing (never seen it, but can work through in my head how it could happen), beginnings of high pressure VANOS line leakage, or pump degradation (you'll know if you're panning for gold on an oil change).

The VANOS performance test may give some diagnosis insight as well. Ignore the silly "quality" metric, but pay attention to the spread times and null current.
 

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Discussion Starter #12
Thanks Jcolley, all valid points. The internal HP line was replaced as per recall sometime in 2007 I believe, when there was somewhere in the neighborhood of 3,000 miles on the car. I'm the 2nd owner, the original had the car for 74K miles. Seepage from the internal line could show as a pressure loss of the accumulator, since that is exactly what is happening (only the oil is leaving the system and not the nitrogen). It only takes a couple of days in the cold to show this low pressure. Once the engine is running, pressure returns to normal, so that should rule out the pump. I also have no oil contamination as per my initial oil change, and I do not have any whining/bearing noise from the pump while accelerating. Oil is with Blackstone currently, awaiting results.

No way to check internal line without removing the subframe and oil pans, and even then, no real way to check short of R&R. I'll see what accumulators go for. If they are in the budget (lol), I'll swap out and see what happens. Oil is 10W60, btw.
 

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If anyone out there has got a dead accumulator they would like to donate to the cause, I'd be happy to autopsy it in my garage and post up some real answers here. This situation might just be helpful for diagnosis down the line. I'm sure the info would be appreciated among the forum members!
 

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Thanks Jcolley, all valid points. The internal HP line was replaced as per recall sometime in 2007 I believe, when there was somewhere in the neighborhood of 3,000 miles on the car. I'm the 2nd owner, the original had the car for 74K miles. Seepage from the internal line could show as a pressure loss of the accumulator, since that is exactly what is happening (only the oil is leaving the system and not the nitrogen). It only takes a couple of days in the cold to show this low pressure. Once the engine is running, pressure returns to normal, so that should rule out the pump. I also have no oil contamination as per my initial oil change, and I do not have any whining/bearing noise from the pump while accelerating. Oil is with Blackstone currently, awaiting results.

No way to check internal line without removing the subframe and oil pans, and even then, no real way to check short of R&R. I'll see what accumulators go for. If they are in the budget (lol), I'll swap out and see what happens. Oil is 10W60, btw.
Ecs tuning has the best price I've seen for $464.69 new.
 
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I personally have never heard of one of those accumulators failing. Most of the time it is the Vanos line. However, what I have experienced with the Vanos line is that when the engine is cold ~ you don't get a Vanos pressure cold until the oil warms up because the pressure is high until the oil warms and thins out.

Some ideas... Do a Vanos bleed and test after that. It may tell you the Vanos pressure is low.

Second would be to check if you are getting the oil pressure sensor error by the filter housing instead of the Vanos oil pressure error. These flash the same red light but are two different things.

-Do three Vanos bleeds in a row. If results are all over the board each time, it is most likely the line

-Check oil pressure sensor by filter housing

-Tell us the fault codes here.
 

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How cold? Are you running with 10W-60?
At least here I used to get a low pressure code at winter time occasionally, when starting a cold engine (with 10W-60). No CEL. 10W-60 gets very sluggish in cold. Now I use 5W-50 and no codes so far.

- Antti -
 

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Oops, I just replied in the other thread and didn't notice this one.

Since you're on 10W-60, I wonder how cold is the weather when you get the code after a cold start? 10W-60 gets pretty sluggish pretty fast when the temps hit the sub-zero. I used to get the low vanos pressure code occasionally at winter time in cold starts. Then I changed to 5W-50, and no codes so far.

Just a thought.

- Antti -
 

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Discussion Starter #18
Oops, I just replied in the other thread and didn't notice this one.

Since you're on 10W-60, I wonder how cold is the weather when you get the code after a cold start? 10W-60 gets pretty sluggish pretty fast when the temps hit the sub-zero. I used to get the low vanos pressure code occasionally at winter time in cold starts. Then I changed to 5W-50, and no codes so far.

Just a thought.

- Antti -
Hey yeah sorry, if a mod could combine the threads that would be cool. My Surface tablet hiccupped and made twins. lol

Anyways, the temps are in the 30s F by me, so around 0 degrees C. It's not incredibly cold, but more of an issue of the car sitting for a few days. The cold, I'm sure affects the precharge, and the sitting around I'm sure causes bleed down.
 

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Discussion Starter #19
I personally have never heard of one of those accumulators failing. Most of the time it is the Vanos line. However, what I have experienced with the Vanos line is that when the engine is cold ~ you don't get a Vanos pressure cold until the oil warms up because the pressure is high until the oil warms and thins out.

Some ideas... Do a Vanos bleed and test after that. It may tell you the Vanos pressure is low.

Second would be to check if you are getting the oil pressure sensor error by the filter housing instead of the Vanos oil pressure error. These flash the same red light but are two different things.

-Do three Vanos bleeds in a row. If results are all over the board each time, it is most likely the line

-Check oil pressure sensor by filter housing

-Tell us the fault codes here.
Thanks for the reply Troy. So I'm getting no red lights at all, or otherwise any indication that there is low pressure. I am pulling these codes from my peake reader, 27b6 VANOS oil pressure. Before start, no code. After start, code is present. If I drive the car every day in a row, code does not come back. if I let the car sit a few days, then start, code comes back. No CEL, no red oil light. No increased emissions, nothing otherwise visible to the driver. Codes only read by Peake reader.

You make a good point about temperature affecting oil pressure. Cold oil equates to higher pressure. This points to a loss of pressure, either accumulator bleed down or a bleed leak somewhere else in the system (that HP internal VANOS line). Obviously, I have no oil leaks or consumption to speak of. Temperature also affects precharge accumulator pressure, if it is a nitrogen charged unit. Could be over time, the nitrogen has escaped the system.

Basically, I'm starting to see this as not much of an issue, as I throw no CELs, nor do I get an increased emission warning. Only real side effect is a brief VANOS rattle shortly after start which lasts half a second or so. My 2000 M5 didn't even have a VANOS accumulator, that came later in the 2001-2003 M5 and was retrofitted solely to remove the VANOS rattle many complained about.

Is that the sole purpose of the S85's accumulator as well?
 

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So I had an epiphany regarding the DME's VANOS low pressure errors last night.

The DME has no idea what VANOS pressure really is. None. Not Possible. Having taken apart more than a few now, I don't know why I never realized this sooner. There is no pressure sensor on the S85 VANOS high pressure oil system. If there was, the ISTA/D diagnostic routine for measuring pressure wouldn't have to connect a pressure transducer on the "T" fitting to carry out the diagnosis, it would just poll the DME for the pressure reading.

So, what causes this code then?

It seems to me that the only way the DME would know if pressure was low is if the VANOS actuators were adjusting timing at a slower rate than expected. This would lead the DME to interpret that as low control oil pressure, this triggering the code.

What does this mean?

I had this on my car 3 years ago, only on very, very cold Maine winter mornings. When my injector failed and I opened my bottom end, I replaced the VANOS pump, the high pressure line, the rod bearings, and switched oils. I also replaced 3 of 4 VANOS solenoids before I started the engine back up. This doesn't help in diagnosing at all, but I never saw the error again. I never received it during any summer months before either.

I know the VANOS pump wasn't the fault, I replaced it with a brand new one to upgrade the gears and my old one is running merrily around in another engine for 25k miles now.

It's possible the VANOS HP line was at fault, or I believe more likely is the VANOS solenoids.

It's amazing we (collectively) have never realized/discussed this before. It really has to make you wonder how many BMW techs over the years could have been lead down the path of pump/line replacement when really the solenoids could have been at fault. Often it accompanies two VANOS bank actuator errors and I know they love to replace those.

Just something I figured I should add to this thread. Still trying to work out the mechanics of the error in my head.
 
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