Intermittent Rumble at highway speed

[BennyM]

Well, I plan on trying the water injection thing this weekend to get rid of this increasingly annoying piniging in my M50. But in the meantime, I have a new problem to attend to: On the freeway, the 525i has recently developed a low rumble, as though I were driving over a freshly grated road or rougher surface. I drive over these surfaces daily and know they are generally pretty smooth. The rumble usually takes place at 65-70mph and lasts about 10-15 seconds. It's only happened 3 times. First time it occured, I thought either they had done some work on the road or I had developed a flat, but the car handled the same--no pulling to one side or anything like that. I tried taking the car out of gear and letting the engine drop to idle; the rumble went away the first time, but not the most recent time. I don't know if this is a suspension, bearing, or tire issue. Could it be the guibo or center baring? Last time I checked that area, all looked fine.

Also, the parking brake seems weaker in the past couple weeks. I plan on adjusting it this weekend, but wonder if there is a correllation between this and the rumble.....perhaps it catching or engaging when it's not supposed to.

Any thoughts? I can't be the only one who has experienced something like this.

Thanks in advance,
BennyM

[BennyM]

i swear I gave more than enough information here. please give me some ideas or some things to check.

[Paul in NZ]

does it happen at the same spots on the freeway???I swear that the e 34 is at the same time the sweetest riding yet the most fussy for road surface ;
I am never in any doubt about the surface I am driving on and at certani places around my region my car rumbles and whines and vibrates at a particular frequency,all reactions to some idiosyncracy of the road surface.I am sure that my relatively light wheels and stiff sidewall 235/45/17,sbridgestone potenzas have a lot to do with it.

[Dan in NZ]

Yeah, I agree with the road surface thing... I get the most amazing whole-car vibration at a certain stretch of road near my house, yet don't feel a thing in the other three cars I drive on it occasionally.

[kentish]

Same thing here with my 540i. Road surface seems to be good but the whole cr shakes ! while on other cars you dont get any vibrartion.

[NielsGalan]

When I have my sunroof open I get a rumbling/humming sound too. When I shut the sunroof the sound disappears. This is both with my wide summer tyres and my "normal" winter tyres.

[BennyM]

It happened for the 4th time today on a very new stretch of freeway that I've driven every week since september. This rumble was also accompanied by a shimmy. But sometimes I get the shimmy without the rumble....I think. Unlike the thrust arm shimmy, this shimmy takes place more in the seat than the steering wheel. My thoughts are rear suspension or brakes....however, I find it interesting that I too have the Bridgestone Potenzas, perhaps they play some role in this. Again, the rumble/shimmy lasts for maybe 10-15 seconds and usually takes place when I''m traveling around 70mph.


Does that help with any diagnosis?

BennyM

[Paul in NZ]

it happens at a particular set of traffic lights,a particular bridge,a particular stretch of road.

[Reidal]

I'd generally agree with road surface but I'd also raise to possibility of a tyre failure? I have had 2 tyres fail at speed.

Delamination or similar may first show at speed for a defective tyre due to the increased stress and temperatures involved.

The instances can become more frequent and at lower speeds as the problem gets worse.

[Mr._Graybeard]

Benny, Did you ever resolve this issue? I'm getting it too (of course) and am at a loss to the source. I bit the bullet about 30K ago and had a mechanic inspect the driveshaft while he replaced the guibo and center bearing. I asked that he make sure the u joint was OK, and he gave it a clean bill.

Nevertheless, every once in awhile I get this rumble from the rear of the car, usually with slightly positive throttle. I've never heard the rumble while accelerating aggressively, or at less than 40 mph. Most of the time it comes on at highway speed, like 65 mph or higher. I've had the car for 115K miles and it's been present for most of that time. It feels kind of resonant, like tires on a rumble strip.

I worried awhile that it was the torque converter clutch going bad, but like I said, it's been an issue for more than 100K miles. I've read forum threads for years in search of an answer. Maybe you have too. I've replaced pitman arms, trans and engine mounts.

Lately I've felt a little more vibration, and I occasionally feel the rumble at a lower level but for a more extended stretch. It's the kind of thing most people wouldn't notice, but after having an ear tuned to the sound, I sense a change. Maybe a control arm bushing has ovaled? Exhaust system has shifted? the exhaust donuts are pretty fresh.

The next step, I suppose, is to pull the rear subframe and replace all the bushings, including the beer cans. The other option is to live with it. The car is coming up on 200 K and has always felt safe and fully stable on the road.

Anyway, it's been a little slow around here, I thought I'd revive this topic and see if some fresh insights have emerged.

[BennyM]

Sorry Graybeard, that was a quarter-life ago for me and I no longer have that particular e34, nor do I think I ever found a definitive solution to the problem. I can tell you I had the car for nearly 4 more years after that post and I don't remember the rumble being a lingering issue, but perhaps too many other issues masked it after a while. I do remember that the drivetrain was in pretty good shape at the time and those tires wore out evenly several years later without a problem. Things that were failing around that time included the exhaust and suspension. A few months later, I installed new lower control arms, sway bar bushings, and rear pitman--- anything that might reduce vibration. I also spent a lot of time trying any trick or chemical that would remove carbon deposits or clean the fuel system because I remember feeling like the engine wasn't as smooth as it should be. I did the BG-44K hot soak, which was popular for a while. I think that might have helped a bit.

I think everyone here can relate to that unpleasant, and all too common, sensation while driving along in these cars that something new is vibrating or too noisy or loose. It definitely takes away from the day to day driving pleasure for me. My newer 525i is in much better shape than the one I had in 2004, but I still get a weird hesitation or a random subtle shimmy from time to time. There are days when everything just clicks and the car seems to drive like new and there are other days when I miss the simple reliability of a new Honda.

I will probably need to revive the rear suspension pretty soon, including the beer cans, but I am dreading that job more than any other to date. I am even considering (gasp) paying someone else to replace the bushings.

[Mr._Graybeard]

Hey Benny, sorry to hear you didn't find the source, but thanks for taking time to respond. The sound is that classic rumble strip growl, lasting just a second or two. I'm suspecting the torque converter lockout clutch -- I'm due for a fluid change and I think I'll give Kirt Koeller a call to see if there's a solenoid I might try checking out while I have the pan off.

It's been going on so long, I've kinda learned to live with it, but I think I've noticed a subtle change in the sound. Coming up on 195K, so the trans may be due to start acting up (hope not).

I hear you on those beer can bushings. There's no grunt work like suspension work as far as I'm concerned. Good luck!