Brake pulsing

nigel911 · nigel911's Garage

My car is suffering from 'pulsing' when braking - it feels as though the front rotors are warped... brake, release, brake, release etc

I have checked all the rotors and they seem fine, they are not warped and are well within specified wear limits, all brakes are running with reasonably new pads.

The previous owner had 'upgraded' to a 22mm (I think) master cylinder from a VW camper van - a mod which he swore by and fitted to all his 911's (3 of). Would this have anything to do with my problem?

Any ideas gratefully received...

Nigel
72 911T

bob tilton · bob tilton's Garage

get it fixed now!!! i felt my brakes pulsing but thought it was a flat spot on one of my rear tires from sitting. long story short, i watched the flatbed haul my car away on the freeway while trying to get my heartbeat back to normal from the near accident. had the entire brake system rebuilt. cause: disintegrated brake lines. do not put yourself or others at risk.
bob
68 L

Planter91C2 · 01-18-2002, 06:44 AM

[QUOTE]Originally posted by nigel911
[B]My car is suffering from 'pulsing' when braking - it feels as though the front rotors are warped... brake, release, brake, release etc

I have checked all the rotors and they seem fine, they are not warped

i think it is warped rotors. how did you check them?

BK911 · BK911's Garage

My money's on warped rotors as well. The rotors can be warped enough to cause a pulsing/vibration, yet not be visually detectable. New rotors are cheap and you'll need them eventually anyway. Install new rotors and have your existing rotors turned. When the new ones develop a lip or warp, put the turned ones on. Then have the other set turned. Repeat until you can't have them turned anymore.

Superman · 01-18-2002, 10:15 AM

Brake pulsing cannot be a master cylinder problem. The problem is at the wheels. Either warped rotor or bearing race that is not fully seated, or something like that.

Bill Verburg · Bill Verburg's Garage

In addition to a rotor problem a likely cause of pulsation in the brakes of an older car is worn out front struts. I have seen this on my own car and several 930s.

Jim Sims · 01-18-2002, 01:00 PM

Also worn out (rotted out?) front suspension rubber bushings can allow excessive play and then pulsation when braking.

Jim

724doorE · 01-18-2002, 05:14 PM

Bill and Jim are right, don't forget the suspension. I rebuilt the brakes on my mustang only to find that I also needed struts. Your T is 30 years old. If you don't know wether any of these things have been done, they probably should be looked at. Besides it is a great reason to upgrade to some sport shocks, urethane bushings and bigger brakes. My two cents.

Dennis H.

72 911E

Roland Kunz · 01-19-2002, 09:54 PM

Hello

Check the wheelbearings and then get a magnetholder and a dail to messure your rotors. If this all turns out good replace the rubber brake hoses and rebuild your calipers ( Check if the pistons are in ther position 15° offline ).

I don´t think the bus MBC will cause the problem ( Pressure is pressure ) but have a look at it as well. Make sure the vent is open when you release the brakes.

Grüsse