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Discussion Starter #1
Background: A while back when my M5 wouldn't pass smog I tried cleaning my MAFS with contact cleaner. There was no change that I could detect, and it didn't fix the smog problem (new cats did, but just barely). I don't think I had cleaned the MAFS effectively. I didn't take them out of the housings, and I don't think much cleaner got where it needed to go.

I think the car is down on power, so I was going to give the MAFS a more thorough cleaning today with soapy water and isopropanol as suggested in another recent thread, when I found that they and the whole intake system were coated with motor oil. Oil was leaking out where the sensor housing connects to the driver's side air filter box, and when I opened it up, I saw that motor oil had gotten on the air filter, and into the bottom of the box below it. I removed the hoses that connect the MAFS to the plenum and found oil in them as well, on both sides. Oil hadn't leaked all the way into the air filter box on the passenger side, but it got into both MAFS housings. I took the plenum cover off and saw that not only was oil pooled a bit in there, but it has coated the velocity stacks and even gotten on the underside of the plenum cover.

When I attempted to clean the MAFS before, there was no oil in them or the air cleaner boxes at all, so this happened recently. I had the dealer change the oil recently, so I checked the level and it was over the high mark, about 1/3 of the way between it and where the plastic widens (it's hard to see in the picture because of glare). Could overfilling have caused this?

I didn't bother cleaning the MAFS. I just took these pictures, put it back together, and called the dealer. I have an appointment tomorrow. I doubt this could have done the MAFS any good, but is there any other damage that could have been done? Is there anything specific I should have the dealer look for?

- Dave


Pictures:

Air filter stained with oil, oil in the driver's side box, on the tube in the cover, on the MAFS housing, etc. Also, notice that the cylindrical rubber gasket in the driver's side plenum connector tube is pushed in and kinked, sticking a bit into the air stream. This can't be good for airflow. I have no idea how long it's been that way since I didn't open that part up before, but it's not related to the oil problem. I'll ask the dealer to put a new one in.




 

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While too much oil can cause excessive pressure in the oil resevoir I cant believe that this alone would cause that kind of bypass of the piston rings. You might want to ask them if a broken ring can cause this. Just a wildass guess here.
 

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Discussion Starter #4
FAST 5 said:
Dave,
What year is your car?
Robert hmmm
It's a 2000 model with 69K miles on it. I've only had it a few months, and it has the CPO 6yr/100K mi warantee.

- Dave
 

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My '01 M5 had this problem once - I got an SES light and when the dealer opened up the air filters both were full of oil. The diagnosis was a failed rubber O-ring seal between the VANOS actuator body and the cylinder head that was leaking oil into the plenum. New O-rings fixed it.

Cheers
JJ
 

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Discussion Starter #6
Pete said:
While too much oil can cause excessive pressure in the oil resevoir I cant believe that this alone would cause that kind of bypass of the piston rings. You might want to ask them if a broken ring can cause this. Just a wildass guess here.
Pete,

Thanks for the response.

So you think it's oil bypassing the rings into the combustion chamber, and out the intake valves into the plenum? That sounds pretty bad.

How could that happen though since the pistons should be sucking air in while the intake valves are open, not blowing anything out through them? Wouldn't oil in the combustion chamber be burned and blown out the exhaust instead? I haven't noticed a cloud of blue smoke behind me or smelled anything funny, but of course I wasn't looking.

- Dave
 

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Discussion Starter #7
jaj said:
My '01 M5 had this problem once - I got an SES light and when the dealer opened up the air filters both were full of oil. The diagnosis was a failed rubber O-ring seal between the VANOS actuator body and the cylinder head that was leaking oil into the plenum. New O-rings fixed it.

Cheers
JJ
Thanks, JJ. This sounds promising. Was there any damage? Did they replace the MAFS because of potential fouling, or anything else?

I got an SES light a few weeks ago and went to the dealer. They found that there were codes still there from when the car wasn't passing smog and the cats were replaced (the other dealer forgot to reset the codes), so they cleared them and said to come back if it came on again. That's when I had them change the oil. I think the SES was related to the emissions problems because the codes were for cats & exhaust sensors. The SES light hasn't come back on, but if this continued much longer and soaked the filters and MAFS more I bet it would.

- Dave
 

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Dave,

I think Pete is talking about the pressure inside the engine building up due to pressure leaking past the rings. You might have a plugged crankcase vent causing the pressure to force the oil back into the plenum via the valve cover vents located at the front of the plenum. Or, the issue JJ talked about sounds likely to.

Good Luck, John

DaveK said:
Pete,

Thanks for the response.

So you think it's oil bypassing the rings into the combustion chamber, and out the intake valves into the plenum? That sounds pretty bad.

How could that happen though since the pistons should be sucking air in while the intake valves are open, not blowing anything out through them? Wouldn't oil in the combustion chamber be burned and blown out the exhaust instead? I haven't noticed a cloud of blue smoke behind me or smelled anything funny, but of course I wasn't looking.

- Dave
 

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I noticed oil on my air filters recently too. The car seems to be running fine and the oil didn't seem to be all the way up into the MAF -- just at their openings and on a 2 inch portion of the air filters. The only reason I noticed it was that I was putting in my K&N filters.

It looked more like oil was sucked up into the filter, but this wouldn't make too much sense either. Sometimes I wash my engine (which collects significant oil in LA) so maybe after I washed it some oil/water was sucked in? :confused2

If there is a problem, I am hoping the SES light will come on . . . hmmm

Please keep us posted on what the dealer says is wrong.

P.S. About a month ago my oil pres. light came on. The dealer said it was a faulty signal. Sometimes I get the impression that the dealer doesn't know what is up either. ouich


DaveK said:
Pete,

Thanks for the response.

So you think it's oil bypassing the rings into the combustion chamber, and out the intake valves into the plenum? That sounds pretty bad.

How could that happen though since the pistons should be sucking air in while the intake valves are open, not blowing anything out through them? Wouldn't oil in the combustion chamber be burned and blown out the exhaust instead? I haven't noticed a cloud of blue smoke behind me or smelled anything funny, but of course I wasn't looking.

- Dave
 

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Discussion Starter #10
jeeperjohn said:
Dave,

I think Pete is talking about the pressure inside the engine building up due to pressure leaking past the rings. You might have a plugged crankcase vent causing the pressure to force the oil back into the plenum via the valve cover vents located at the front of the plenum. Or, the issue JJ talked about sounds likely to.

Good Luck, John
Thanks for clearing that up, John. It makes a lot more sense to me now.
Hopefully that's not it, bad rings would be a worse problem than the issue JJ had. I'll suggest that the dealer do a compression test. I'll let you all know what they find.

- Dave
 

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Dave,

I don't think it is a ring problem since the problem showed up suddenly, more likely the vents or seal issue that JJ mentioned. You can have the dealer check the crankcase pressure to see if the vents are plugged. Did you have oil leaking from the oil fill cap?

John

DaveK said:
Thanks for clearing that up, John. It makes a lot more sense to me now.
Hopefully that's not it, bad rings would be a worse problem than the issue JJ had. I'll suggest that the dealer do a compression test. I'll let you all know what they find.

- Dave
 

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Discussion Starter #13
jeeperjohn said:
Dave,

I don't think it is a ring problem since the problem showed up suddenly, more likely the vents or seal issue that JJ mentioned. You can have the dealer check the crankcase pressure to see if the vents are plugged. Did you have oil leaking from the oil fill cap?

John
John,
That's reassuring. Hopefully you're right about it not being a ring problem.
One of the pictures I took shows the cap. It looks like some oil may have leaked, but it's not too bad. It's hard to tell if it leaked or if some was spilled when they filled it and didn't clean it up completely. I'd take a closer look but the way it's parked in the garage I'd have to pull it out and I'm too lazy to do it this late.

Ocean-Side,
If it has anything to do with overfilling or a warrantee issue I would hope that they would clean it up. They ought to replace at least the one filter it leaked on as well. It's a K&N though, and I doubt they would replace it with another K&N. I was contemplating putting stock air filters back on it anyway. And the MAFS will definitely need cleaning now.

- Dave

 

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DaveK

My 2001 had 3,000km when I got it.

There was no damage at the time, and the MAF's never did fail, but later in life I had more codes and the VANOS actuator was replaced, and then I had more codes and a cam sensor was done. That's one reason I'm driving a brand-new (16 months ago) 2003.

The dealer master tech blamed the original O-ring problem on overheating of the cylinder head, but I don't know if that's credible. He did show me the O-rings and they were hard and cracked (as opposed to nice and soft), but I'm not sure that wouldn't be normal after use.

Cheers
JJ




DaveK said:
Thanks, JJ. This sounds promising. Was there any damage? Did they replace the MAFS because of potential fouling, or anything else?

I got an SES light a few weeks ago and went to the dealer. They found that there were codes still there from when the car wasn't passing smog and the cats were replaced (the other dealer forgot to reset the codes), so they cleared them and said to come back if it came on again. That's when I had them change the oil. I think the SES was related to the emissions problems because the codes were for cats & exhaust sensors. The SES light hasn't come back on, but if this continued much longer and soaked the filters and MAFS more I bet it would.

- Dave
 

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Discussion Starter #15
Update

Thanks to everyone who responded. Here's an update:

I brought the car to the dealer on Wednesday afternoon, and they finally had a diagnosis today. It's the same problem JJ had, a failed O-ring on the VANOS system. They ordered the part and expect to have it Monday. They said they cleaned up the oil, but didn't indicate that any damage was done. They said they didn't think the oil got up into the sensors on MAFS, just in the bottom of the housing tube.

They also advised me to replace the K&N filters with stock ones or any future problems with the MAFS may not be covered under warrantee because of the known issues with K&N oil fouling them. I plan to get stock replacements when I pick up the car, and give the MAFS a good cleaning. Do the K&Ns really do much for performance on this car anyway, before they foul the MAFS that is? Are there any alternatives that flow better than stock ones but aren't oil coated?

- Dave
 

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Dave--->Maybe you could ask the tech why the O-Ring would fail and what are the likely causes...

I wonder if it's possible oil aditives or chemically caused, or because they were pinched during install or if they could have gotten weak over time?

hmmm
 

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Re: Update

DaveK said:
Thanks to everyone who responded. Here's an update:

I brought the car to the dealer on Wednesday afternoon, and they finally had a diagnosis today. It's the same problem JJ had, a failed O-ring on the VANOS system. They ordered the part and expect to have it Monday. They said they cleaned up the oil, but didn't indicate that any damage was done. They said they didn't think the oil got up into the sensors on MAFS, just in the bottom of the housing tube.

They also advised me to replace the K&N filters with stock ones or any future problems with the MAFS may not be covered under warrantee because of the known issues with K&N oil fouling them. I plan to get stock replacements when I pick up the car, and give the MAFS a good cleaning. Do the K&Ns really do much for performance on this car anyway, before they foul the MAFS that is? Are there any alternatives that flow better than stock ones but aren't oil coated?

- Dave
Dave ...

To answer your question ... It is a 2-fold answer answer ... Yes the K&N filters add a little to performance IF for no other reason than they allow "More AirFlow" than the stock paper filters ... Thise are a complete waste.

IMHO ... The best all around is the Dinan CAI with the Larger Air Flow meters. My reasoning is primarily this ... WARRANTY is STILL VALID if the DINAN work is done at a BMW-Dinan Dealership. All of my Dinan work has been done at a BMW-Dinan Authorized Dealership and my BMW warranty is entact ... 100%!!

To me ... That right there is worth the price of admission!

No strange looks from leary Service Managers ... no "What the Hell is that?" type of discussions ... NO "Let's see what other mods this guy has" ... No Problems ... Just Yes Sir and Thank you very much for having your work done here. I just had BOTH CATS replaced under warranty. I suppose it's possible that the Tubi exhaust ... with less back-pressure ... helped the CATS gets mucked up and clogged ... BUT ... So far ... In 1.5 years of ownership ... Everything has been repaired under warranty.
 

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Discussion Starter #18
Re: Update

gra8fuldd ed said:
Dave ...

To answer your question ... It is a 2-fold answer answer ... Yes the K&N filters add a little to performance IF for no other reason than they allow "More AirFlow" than the stock paper filters ... Thise are a complete waste.

IMHO ... The best all around is the Dinan CAI with the Larger Air Flow meters. My reasoning is primarily this ... WARRANTY is STILL VALID if the DINAN work is done at a BMW-Dinan Dealership. All of my Dinan work has been done at a BMW-Dinan Authorized Dealership and my BMW warranty is entact ... 100%!!

To me ... That right there is worth the price of admission!

No strange looks from leary Service Managers ... no "What the Hell is that?" type of discussions ... NO "Let's see what other mods this guy has" ... No Problems ... Just Yes Sir and Thank you very much for having your work done here. I just had BOTH CATS replaced under warranty. I suppose it's possible that the Tubi exhaust ... with less back-pressure ... helped the CATS gets mucked up and clogged ... BUT ... So far ... In 1.5 years of ownership ... Everything has been repaired under warranty.
Thanks for the advice.
Are you saying that K&Ns alone are a complete waste, or the stock paper filters are? It wasn't clear to me.
I already have the AA CAI kit, which came with the K&Ns (I think - the previous owner had it put on). I suppose I could add Dinan's larger MAFS to it, but I'd rather not spend the money on those since even in combination with Dinan's CAI kit and higer flow exhaust it only gives 6 more peak HP. Does the Dinan kit come with K&Ns? If so, are their MAFS made to handle the oil?

I also got both cats replaced under warrantee recently when it wouldn't pass smog. Luckily they didn't give me a problem with the AA CAI or K&Ns. Also, it was obvious that my current problem wasn't caused by those.

Ocean-Side: When I pick it up I'll ask them what they think caused the O-ring to fail.

- Dave
 

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Discussion Starter #19
Update

I finally got my car back from the dealer yesterday. They found internal leaks in both VANOS units, and pulled them apart. They put them back together with all new seals (gaskets, O-rings), and replaced the crankcase valves and one of the MAFS. I asked them what caused it and all they could say is that the seals went bad.

While I was picking the car up I bought stock air filters to replace the K&Ns. While putting them in I noticed that there was still some oil residue left in the intake, so I took it apart again and gave it a better cleaning, and cleaned the MAFS with soapy water, then isopropanol, then contact cleaner spray. That way I'll know for sure if the problem happens again. I took it for a spin and it runs fine. I checked the intake again and found no oil. I'll check it again in a few weeks, and hopefully the problem will not come back. Thank god for the CPO warrantee!

Thanks for all the replies.

- Dave
 

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Re: Motor Oil Coating Intakes

Dave, thanks for the detailed thread on this problem. I've called it back up because my dealer here in SC has informed me that oil residue in the intakes is normal hmmm , and does not plan to correct this condition on my engine. The amount of oil residue that I have is similar to that reflected in your pictures, and in my observations, it's more significant on the passenger side than the driver side.

I was wondering if anyone could confirm/deny this claim by my dealer's Master Tech. Do the rest of you have oil in your intakes? (I've got 55K miles on this engine)

That said, I recognized the "vents", or perhaps better defined "drain" holes on the bottom on the intake tube just before the connection to the OE air filter assembly. I speculated these might be for the purpose of draining oil if in fact it did coat the intakes (by design?!?!?):blabla:

Also, if any of you have had this "problem" corrected - what were the part numbers from the work order, and did the corrective action solve the problem.

Thanks!
 
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