cold days

[6-speed]

My 540i vibrates at highway speeds if the engine is not fully warmed up. Does anybody know why? I'm thinking the engine mounts or some pump? Thanks for your help.

[Furious]

is it an actual feeling or sound?

[6-speed]

it's an actual feeling. thanks.

[CBA]

hmm is it intermittant or constant.

[TECH]

Is it misfiring? What year, miles?

[6-speed]

the car is not misfiring and it only happens until the car is fully warmed up and only if I reach speeds above 55 mph. 540i with 6 speed 29000 miles

[Furious]

well mounts would be constant, pump will not really give any definative vibration and ceraintly wouldnt be intermitent. what does you fan look like (behind the rad not in front) has it lost or loosing the edges or peices? it could be off balance. also check your tension pully, push on it and it should move with no problems, if it squeeks excessively or takes some serious muscle to push then it could be your problem, i personally had the problem just this week with the Tension pully and it gave me a slight vibration but not too noticeable more of a sound.

lastly check the brakes, see if you may or maynot have a caliper sieze (also check the parking brake even thou you said it feels like it comming from the front.)

[TECH]

I would check the fans, both the clutch and the auxillary. Possibly the water pump.

[6-speed]

what signs and symptoms can you look for to see if the brake calipers have seized or stopped working properly? Thanks.

[CBA]

if the calipers are fucked the best way to tell is to remove them and try to manually depress them back into the cylinder.. just becareful ya dont wanna fuck up the piston..

[EXtech]

6-speed, do you feel the vibration in the wheel, seat or tail end of the car?

[6-speed]

i can feel it in the seat and it feels like the whole car is vibrating

[EXtech]

Furious has got some good ideas. However, if your vibration is only occuring at a particular speed (55mph in this case) and not engine rpm (no fan theories) and only from cold to operating temp, then I would first suspsect that you've got something going on chasis and/or driveline related. I would look at tires first because they are the quickest and easiest to test. Under inflated tires will cause the problem you describe (especially in colder climates). Check the air pressures in your tires and make sure they are at the proper cold temp specification before you leave in the morning. If you don't have access to air at home, on your way home in the evening inflate the tires 7-10 psi over cold setting (less if in warmer climates). This should put them at cold spec in the morning. Give that a shot and see if your problem persists. If that doesn't work, then keep increasing the pressures slightly and note the changes. If nothing improves then you will probably have to take it in. (booger. I know) Let us know what happens. Unfortunately this is a hard one to accurately diagnose without actually driving or riding in the car.

[6-speed]

I'll give it a try. Thanks.

[6-speed]

I tried the increasing the tire pressure business, it didn't work. I'm taking it in soon but because it's an intermittent problem on cold mornings, I don't know if they can find the problem. We'll see.