[Capn Crunch]

My 2011 335D has started to have a vibration while the transmission is in Drive and the car is stopped. (i.e at a stop light) I have noticed it more when the car is below normal operating temps. I checked the intake tract for unmetered air and fixed a couple of potential issues. This lessened the vibration but didn't completely fix it. Once the car is warmed up the issue seems to go away completely. I have torqued the transmission mount bolts and the rubber seems pretty soft. Visually the engine mounts look ok but is hard to tell.

I think it maybe coincidence, but this issue started after replacing a bad harmonic balancer. I understand how the harmonic balancer works and that it correlates to vibration but I don't think that engine temps would affect it as much as it does.

I have also seen many other issues of similar issues with other BMWs but not much tied directly to the D.

Any other ideas?

[335dlci]

When i worked at the dealer, i was one to normally get customer complaints such as noises....your description is pretty vague. Where is this noise coming from? Have you pin pointed the location of the noise? Items stuck in the rails of the seats, door panels, all the little cubby hole areas can all produce noises with stuff in them. Without really pin pointing where the noise is coming from makes it ard to figure out. There are test plans in ista D for squeaks,rattles, buzzing.. etc to help with diagnosis.

[Capn Crunch]

Sorry. It's not a noise that I am hunting. It is the cause for the vibration and transfer into the cabin. It is a vibration you can feel throughout the entire cabin of the car. The entire engine vibrates. You cannot feel it on the exterior panels. If you apply a tiny bit of throttle to bring up the RPM, then the vibration goes away.

I put some power service Diesel Kleen in the tank to see if it helps by cleaning the injectors over the next couple of tanks. Maybe I can Isolate it to an engine component.

[Yozh]

Check if your engine mounts hold vacuum and the vacuum supply to them.

[335dlci]

Originally Posted by Capn Crunch

Sorry. It's not a noise that I am hunting. It is the cause for the vibration and transfer into the cabin. It is a vibration you can feel throughout the entire cabin of the car. The entire engine vibrates. You cannot feel it on the exterior panels. If you apply a tiny bit of throttle to bring up the RPM, then the vibration goes away.

I put some power service Diesel Kleen in the tank to see if it helps by cleaning the injectors over the next couple of tanks. Maybe I can Isolate it to an engine component.

Ahhh . I would follow yozh's tip and check the mounts.

[die$el<3]

I had the same issue and it was my engine mounts. When the car was cold it was a lot worse

[Capn Crunch]

The engine mounts hold 24 inch hg of vacuum as well as the supply. The mounts also visually look fine. Can they still be bad or is that the only diagnostic for the mounts?

[Yozh]

Originally Posted by Capn Crunch

The engine mounts hold 24 inch hg of vacuum as well as the supply. The mounts also visually look fine. Can they still be bad or is that the only diagnostic for the mounts?

Check what vacuum is supplied with an engine running at idle and at over 900rpm. The best thing you can do is hook an extra t-fitting inline with the vacuum supply for the mounts and route an extra line with your vacuum gauge to the cabin and see what happens when you drive. The reason for this is if you have anything else compromised within the vacuum and turbo control system it may not show up at idle or off boost. But will affect your mounts vacuum supply. I remember they are soft at idle but can't remember if vacuum is on or off for that. When testing you can easily check by looking what happens at idle.

[kydiesel35]

Originally Posted by Capn Crunch

I think it maybe coincidence, but this issue started after replacing a bad harmonic balancer. I understand how the harmonic balancer works and that it correlates to vibration but I don't think that engine temps would affect it as much as it does.

Check the HB. Just in case..

[Capn Crunch]

The new harmonic balancer is visually ok. Other than putting another HB on the car I don't know how else to test the HB. I did notice some CBU on the EGR valve last night.

I will test the running vacuum later today. The vacuum at idle is 24 inch hg.

[Capn Crunch]

Started doing a CBU cleaning. The disassembly is easy, the cleaning is MESSY! Just have to blast the intake ports tomorrow evening and put her back together. If nothing else it will eliminate it as a possibility for the vibration... and it needs to be done anyway with the car at 75k miles and the amount of build up.

[Capn Crunch]

Finished up the CBU cleaning tonight... it did not fix the problem. The engine does run a lot smoother at idle in park, however, the vibration still comes back when you put it in drive.

[Yozh]

Originally Posted by Capn Crunch

The new harmonic balancer is visually ok. Other than putting another HB on the car I don't know how else to test the HB. I did notice some CBU on the EGR valve last night.

I will test the running vacuum later today. The vacuum at idle is 24 inch hg.

How old is your harmonic balancer. And for the record, at idle, my vaccum system is at 29 inHg. I believe our vacuum pump is spec'd at min 0.9bar. I'll check.

EDIT: I have checked and am confused. One Pierburg doc shows -1000mbar relative, another shows 0.7 to 0.9 bar of vacuum, but that may be for piston and not for single vane pumps. Then our BMW Diesel Technology doc shows -500mbar absolute. May be others can measure for you to confirm. I would check what the actual vacuum pump pulls.

[Capn Crunch]

The harmonic balancer is ~ 1500-2000 miles old. But I have ruled out the harmonic balancer because it won't see load force based on transmission input at idle in gear, any different than it would in park or neutral... In other words it would vibrate at idle under load or in park if it was the HB also it is unlikely that the running temps would affect the vibration how they do. . The engine is running extremely smooth and quiet after the CBU cleaning at all RPM in park or neutral, so that tells me it is either in the transmission or the engine mounts. I am leaning towards engine mounts... but I think your on to something in the vacuum supply. I will try to get a different reference with a better vacuum gauge. I was using a loaner Mityvac pump from Autozone and would just want to verify. I will check with an isolated vacuum gauge to ensure nonleaks and accurate gauge readings. I also think because of the correlation to temps that it is caused somewhere in the engine mount system because the computer references engine temps or speed for activating the engine mounts.

[Yozh]

I'm sure you have seen this, but just in case and for others:

[Capn Crunch]

Yozh thank you for posting that. I have not been able to find this direct information. I have two more vacuum tests... engine running with no vacuum supply to engine mounts and manual vacuum applied to engine mounts. But I have to wait for the car to be cold. I verified all other readings with a brand new vacuum gauge and vac pump. My running vacuum is 26 in hg at idle and 28 at 900 RPM and above.

[Yozh]

Mine tends to agree with the Pierburg chart provided below. 1000mbar is 29.5inHg. Mine coincides with that value. May be others can confirm as well.

[Capn Crunch]

So I ran 3 more tests. The engine mounts hold full supply of vacuum (26 in HG) engine off or at idle with no load (i.e in park or neutral) as soon as you put the car in gear the vacuum, between the mounts and the vacuum switch, drop to 10 in hg of vacuum and fluctuates by 2-3 in hg of vacuum... in all other instances the vacuum is steady. Now I just need to isolate which mount it is.

[Torqu3]

Originally Posted by Capn Crunch

So I ran 3 more tests. The engine mounts hold full supply of vacuum (26 in HG) engine off or at idle with no load (i.e in park or neutral) as soon as you put the car in gear the vacuum, between the mounts and the vacuum switch, drop to 10 in hg of vacuum and fluctuates by 2-3 in hg of vacuum... in all other instances the vacuum is steady. Now I just need to isolate which mount it is.

How did you test that? My car is having the same issue, although it may not be as bad as yours. I just attribute it to a normal diesel shakes, but I could need to replace engine mounts. It's worth diagnosing anyways.

[Capn Crunch]

Yozh posted a document above for a visual reference to the hose routing. Although the it in not to scale it will help you understand my explanation.

To test your vacuum get a hand held vacuum pump/ brake bleeder with gauge. Use a t fitting and a short piece of hose to T into the vacuum supply line coming from the vacuum switch at the rear of the engine below the intake manifold. You will disconnect the black rubber hose with the red chaser line from the vacuum switch. This loops down to a t fitting the splits to both engine mounts. Connect the short hose to the vacuum switch where you disconnect the rubber hose. And then connect the rubber hose you disconnected to the other side of the t. The vacuum pump and gauge should be attached to the 3rd port on the t fitting. Start the car and check your reference vacuum. If it is holding steady in the mid to upper 20s in hg, have a friend put the car in drive to pit load on the engine, if the vacuum drops you have a bad motor mount.

If it is an unsteady vacuum or it is lower than 20 while in park then you should check for leaks. If there are no leaks in the line then it is a motor mount.

To isolate which motor mount is bad, return vacuum hose routing to normal. Underneath the drivers motor mount is the T fitting that has the black and red rubber supply line and a braided line that goes to each mount. Pull the hose that goes to one of the motor mounts and connect your vacuum gauge to that port on the T. The motor mount still hooked to the T is the mount you are testing. Turn on the car and test the vacuum in nuetral and in drive. If the vacuum is normal in park but drops in drive, that is your bad mount.

Mine ended up being my Drivers side mount. I am ordering one now.

[Persian Whisperjet]

Yozh I had no idea all of this was going on under the hood.

[Capn Crunch]

So I finally got the new motor mount in. Put it in the car tonight... a vibration is still happening. It is only in 1st gear. If i shift it manually in to 2nd the vibration goes away. It no longer vibrates in reverse. My next step is to try a transmission fluid and filter change. Any other ideas?