'95 740i pulsing while braking

[meredijh]

I have a '95 740i with about 114k miles. Under moderate braking, I get a pulsing sensation through the pedal and steering wheel. I've replaced the thrust arms and control arms. The problem is not as bad but it is still there. I also replaced the front and rear disc pads about 5k miles ago and had the front discs turned to remove slight ridges (they were not warped). At this point, I'm trying to decide if it is the front wheel bearings (aka, hubs) or if I need to buy new front discs. Any hints on troubleshooting? Any other areas I should consider?

[lincolnmaster80]

Originally Posted by meredijh

I have a '95 740i with about 114k miles. Under moderate braking, I get a pulsing sensation through the pedal and steering wheel. I've replaced the thrust arms and control arms. The problem is not as bad but it is still there. I also replaced the front and rear disc pads about 5k miles ago and had the front discs turned to remove slight ridges (they were not warped). At this point, I'm trying to decide if it is the front wheel bearings (aka, hubs) or if I need to buy new front discs. Any hints on troubleshooting? Any other areas I should consider?

Have you checked for dirty/broken ABS Sensors? Usually when you brake under slippery or even hard brake on dry pavement, the tires will lock up and that's what the ABS will do when it kicks into action. If it's doing that under normal operation (ie, no slippery driving and no heavy braking) your ABS sensors might not be sensing properly and "thinking" that theres a wheel lock up when there actually isn't. I'm not sure about feeling that through the wheel, but then again, I haven't really noticed. Just giving you another possibility!

[meredijh]

Problem Resolved - After driving a couple hundred more miles, the shaking while braking got worse and the bearings started making that noise they make when going bad. So, I changed the front wheel bearings (aka, hubs) and the problem was much better - but still not totally right. The only thing left was the front rotors. I changed those out today and the problem is solved.

The rotors must have had a slight warp that highlighted the fact that the bearings were worn out. I guess I'll add my experience to others that say don't bother turning BMW front discs - just buy a new pair. I had mine turned just a bit to take out the small ridges (they were not warped). They didn't last 5,000 miles after that.

[lincolnmaster80]

Turning the rotors accomplishes nothing, if very little at all. Even if the problem does seem to go away, it'll soon show up again shortly afterwards. It's basically a cheap way to get lots of money out of you...

Glad to hear you've got it fixed! Happy motoring!

[Bear]

Good news for you. It has been my experience that the rotors on these cars (I have a '88 750) are almost impossible to turn as they are, when at pad replacement time, (or when they start to pulse), already at minimum thickness.