Last Lemming

So I was drive my 951 and I noticed that it started making a metal creaking sound. I was pulling into the garage at work when I noticed this so I was by myself and couldn't have someone press the brake pedal to allow me to look around while it was happening, but form what I heard so far it sounds like its coming from under the car. It does not make this sound when he clutch is depressed all the way with force or the accelerator, just the brake pedal. There is no extra pedal effort required when driving either, and happens while the car is on or off. I did rebuild my brakes recently, though this sound didn't happen after I rebuilt them.

I'm hoping its not a cracked firewall.

Last Lemming

So I had a work buddy press the pedal so I could have a look around. But without being on a rack or my ramps. I heard the creaking sound loudest in the front right wheel arch. Almost like it was coming from the suspension. I'm not sure why It would be making a creaking sound there. I listed just above the brake booster, but I didn't hear it that loud there - but it was very close and louder in the front right wheel well.

Last Lemming

OK I finally a got a chance to get the car up on jackstands. I pulled the wheels and and the wife pressed the brake pedal.

Put simply this one has me stumped. The sound is definitely coming from the brake caliper region. And the sound is happening on both the left and the right brake caliper. It is much louder on the right side though. I pulled the brake pads and re-lubbed them thoroughly and the sound still persists. You can feel the creak through the strut body and the brake caliper.

The only thing I can think of is when I rebuilt the front brake calipers I didn't lube the O-rings inside correctly. Maybe they are sticking - slipping - sticking - slipping as the piston extends thus making the sound, is this even possible?

CliveB

I have had the same noise for years on my pre-ABS (1986) 951.
I have not had the calipers rebuilt and have no idea what is going on.
Brakes still work OK but pedal is soft. However, I don't think the two issues are connected.

Last Lemming

After a bunch of research last night I have concluded that what Im hearing is the caliper seals rubbing against the caliper piston. I can only imagine due to loss of lubrication. The question is what is the best fix. D

Option 1. pull the pads, remove one bolt on the caliper, loosen the other, tilt the caliper down, extend the pistons into a piece of blocking so they don't pop out, spray with brake cleaner then lube in place by spraying a lubricant (silicon based?) and finally push pistons back in. Will this even work. I've read on other forums for fords and GM vehicles this was the TSB fix. They used a brand called Kluber. My only concern with spraying a liquid if it gets behind the scraper ring the ring may hold fluid in a may get on the pads and rotors later on. I

Option 2. Pull the caliper off the car, pop the pistons out one by one and re-lube seals with ATE Plastilube. Reinstall on car and bleed brakes system. do I need to bleed the rears too if I cap the open end of rigid brake hose as soon as I disconnect or can I just bleed the fronts. I have Motive bleeder.

I know option 2 is better, but will option 1 work. I hate the idea of removing the pistons again!

I found this video from a Cadillac that shows exactly what Im hearing but worse:
http://www.bing.com/videos/search?q=...CAEC98413BD3F7

Last Lemming

Ok. I've pulled the calipers. I have 4 Pistons per caliper, 2 of the 4 Pistons are notched so that only 180 degreses of the circumference of each piston actually touches the pad. I know on non-turbo 944's there are only 2 Pistons and the have the same notch that must be rotated 20 degrees. However i cannot find if the same applies to mine. Can some one chime in and let me know if the need to be rotated or not. Right now I have them set straight up and down.

lovemyp-car

I have the same sound on my 86 951, watching to see if lubing the pistons fixes the issue.

Good luck!
Ethan

sm

I had the same noise on my former 86 951. It had a metal "stretching" feel and I decided to replace the front calipers with new-to-me units and the problem was solved. I wonder if this is a problem with 86 cars?

mel_t_vin

Nope.

No noise/vibration here...not for the last, un-molested, 65k [of 195k] on my watch.

Third owner. Second owner barely drove the car...20k in 6 years. Would have to as the first owner, 110k in 6 years, whether he rebuilt the calipers during his stewardship.

Last Lemming

Ok. So it seems that it was the piston to seal interface. That was the culprit. Lubed them up an all is good.

asmperformance

I've seen a lot of cracked firewalls behind the brake booster on all the 944s. Don't overlook that possibility when doing your checks.