XSeries-forum

Right. You are probably getting fed up of me posting problems on here.. Anyway, today on the drive with the engine running (4.4 M62tu) and in park, I accidentally trod on the accelerator pedal while arguing with the dog..
I was quite surprised to feel a really bad vibration throughout the car at 4000rpm upwards.
Needles to say I tried it a few times again and sure enough it does have a vibration. It’s Ok at idle but I have noticed that there is a sort of drone / fine vibration or hum at about 1500- 2000rpm when pressing the throttle. I don’t often Rev the motor past 3000rpm so I can’t say for sure if it vibrated before the transmission rebuild or not. It’s definitely a lot worse over 4000rpm. .
What your thoughts, comments or experiences?
I did try new motor mounts a while back but the vibration was worse so I put the old ones back on - this was probably due to cheapo parts and as far as I know , failed motor mounts generally show up at idle.
I’ll check for a high rpm misfire but I don’t think that’s it.
I want my car to be smooth..

Engine vibration damper maybe? There’s one on the drive pulley at the front where the alternator and ac compressor belts are. It’s the larger one with 8 bolts.

Other than that, yes I’d be looking for a misfire/bad plug/bad coil pack/bad lead under high load (aka higher voltages).

The gearbox shouldn’t be doing anything as no gear is selected and the torque converter is (or should be) balanced.

The damper did cross my mind. How can that be checked?
Fortunately I’m a lazy driver so 4000rpm is virtually never got to. Tomorrow I will drive it higher up the rpms to see what happens. It’s something I’m determined to get to the bottom of..

I’m guessing that it’s two metal rings with a rubber/elastomer block in between and if the rubber has deteriorated it will allow excessive movement in the outer ring?

Given the transmission has been out, it just might be the flywheel though. Only a very small ‘might’.

Also worth having a look at the PAS pump. Not unknown for cracking in the mounts (metal fatigue). Rare though.

I may take it back to the tranny shop so then they will diagnose it for free as it’s under warranty. I don’t think the flex plate was taken off and I can’t see them not balancing the torque converter.
My reader didn’t say there was any misfires.

I've had a look at the balance pulley - it's a bit tight from the top but I've taken a photo. It looks pretty rusty to me.. I wonder if it is that.
The car is going back to the transmission shop next week at some point so they will take a look.

Loose/out of balance prop shaft mount/centre bearing or fixing. Front prop shaft loose or doughnut split ?

Thinking out loud on the things that would have been disturbed.

Can’t be - it’s when it’s stationary in P or N. It must be either misfire, motor mounts (unlikely), harmonic balance pulley or - and this is throwing out there a bit- clogged catalytic converters. The reason I say that is because I came across a comment on some forum somewhere and the guy had a V8 (not bmw) with similar symptoms. His was partially blocked cats and it only became apparent at high rpm.
It could also be the transmission mounts as that would have been disturbed during the rebuild.

Note to self "read full post!!"

Back to rotating stuff then that may just be getting tired. I had to replace the engine damper due to the Jesus Bolt being loose (if your doing this get a 3/4 drive extension bar a 6' piece of scaffold pipe and a degree gauge ) belt tensioners can go quite quickly as well. Check the engine driven fan for any damage to blades (mine had several big chips). With the fan off and belts removed it is easy to check the water pump bearing and those on the alternator, AC pump and power steering
When I did the job I took the opportunity to remove the engine driven fan and fit an electric fan and shroud from a facelift 4.4 controlled by a thermostat in the top hose

I’ll have a butcher’s tomorrow.
On a different note, I’ve just done a 200mile trip and it did 27.4 mpg according to the screen. I don’t think that’s too bad.

I got under it today to take a look. The harmonic pulley looks ok and is firm.
I did find that the PAS pulley moves in and out by 2-3mm. I don’t know if that’s normal or not but I don’t think it’s the source.

I did some more revving and noticed that if I Rev it up quickly then it’s more apparent. More investigation required..

Coil pack maybe? Dodgy plug or HT lead? Slow VANOS response? Just thinking out loud…

Ok. Update on this.. I haven’t bothered doing anything for a while but the other day I got under it to have a butcher’s.
The only thing I noticed is that the n/s cat rattles a bit. I have noted too that the drone / vibration isn’t as evident when the engine is cold. When it’s hot the problem is a lot more pronounced.
Could the heat expansion of the metal around the cat honeycomb thus allowing it the vibrate be the cause? I may drill a couple of small holes in it and screw in some self tappers to hold the honeycomb tighter to see what happens.
What is confusing though is that it only drones under load at 1500rpm and not when in N or P. If it was the cat the surely it would also do it when not under load.
Other that that all I can think of is the trans mount / motor mounts maybe.
To be continued..

Sounds to me like its torque convertor judder???...you can get this which does work:

https://www.ebay.co.uk/itm/122724735314 ... qOEALw_wcB

No it’s not that. I’ve just had the tranny refurbished and in fact I had TC judder when I first got the car 7 years ago so I know what that feels like.
This is something else. A drone / fine vibration through my feet ( well I can feel it anyway) between 1500rpm through to 2000rpm on part throttle acceleration.
If it’s in P on idle you can barely tell the motor is running. If I put it in D or R then I can feel the engine.
It has to be either motor mounts, trans mounts or exhaust mounts. I think. Maybe.
One other thing that sprang to mind was the intake rubber pipe. I cut off the resonator box part on it a few years ago for some reason but can’t remember why. I wonder if that has anything to do with it? That doesn’t explain the fine vibration though.
I really need to get this sorted as I’m scouring the classified again and I’m not really sure I actually want to get rid of the X5.
Come on get your thinking caps on..