Ed Scherer

Any updates on this?

I'm another interested party... just finished replacing all my brake pads and replaced both front and rear brake hoses.

And... like an idiot, I was fighting with some bleeders that wouldn't bleed (happened on three of the bleeders; I am not a fan of Speed Bleeders anymore) and was focused on that end... I managed to run the reservoir dry and pushed some air all the way through to the caliper Argggghhhh!!!

Anyway, I've bled all calipers and the MC twice (combination of Motive Power Bleeder and pedal depressions) so I'm not seeing any bubbles anymore, but the pedal is still soft. Hard (pretty much same as I remember) with engine off, but I'm pretty sure it's softer (more travel) with the engine on. I haven't put my wheels back on to take it for a spin (have a couple of other things to do while the car is in the air), so it might not be that bad; I'll see. Perhaps a re-bleed after I get a chance to activate the ABS will improve things a bit.

Anyway, I've tried to read through all these "Nicole soft brake" threads since they have so much good info on bleeding.

But... I don't believe I've seen any posts that indicate that this unbelievably long-running problem with Nicole's car has been solved.

Ron_H

The last time I spoke to Nicole it hadn't been resolved. I doubt it has yet. My brakes are next. Either new calipers or re-building my old ones, so I need to decide. I really don't want to experience what Nicole has experienced. I think the only benefit is she isn't putting any mileage on her 928.

Mrmerlin

not driving the 928 isnt good for it

Nicole

Hi Ed:

No, it has not been resolved. My bleed count is 18 times now, with little improvement, if any. I don't feel comfortable driving the car, and am scared to drive it hard or to get into a critical situation. The time it takes to get from gas pedal to pressure point is waaay too long (about 2" more than usual), and the pressure point is still soft. As you describe, this is when the engine is running.

One bird whispered into my ear that the right rear brake line is the hardest to get air out of, but after 18 bleeds that should have taken care of itself. We used the power bleeder, foot pumping, reverse bleeding, and the Porsche dealer's system without success.

The pedal feel - at leas to me - is clearly that of air that needs to be compressed before the brakes respond. We have established that replacing the master cylinder, or activating ABS pump and valves has no effect on this.

One German mechanic who specialized in 928s now sent me the following instructions:

1. Bleed master cylinder
2. Then bleed front calipers
3. Bleed rear calipers last

He also writes that it often helps to lift the car in the front as much as reasonably possible.

Please keep me updated on what you find - hopefully we can learn from each others' experiences and get our cars on the road again soon.

Ed Scherer

As I was thinking about this more, I remembered one thing that might have already been covered in one of these "Nicole's brakes" threads, but it goes all the way back to 2002 and you can read about it in the thread "Those Bloody Brakes". At that time, after having started with air-filled calipers (new "Big Red" fronts and removed/repainted rears) and bleeding, I had the "soft pedal" problem.

After going through some bleeds and still being pretty sure I had trapped air, I (see post #9 in that thread) finally unbolted the calipers and rotated them and rapped on them with a rubber mallet while bleeding. Sure enough, some more air bubbles were dislodged and bled out.

After that, I was satisfied with the brakes.

Today, I tried hitting the calipers (while mounted) with the rubber mallet and did manage to dislodge some really small bubbles. But it does make me wonder if after you have significant air in the calipers if it gets trapped somewhere where the calipers need to be rotated to free the air.

Having never split a caliper open to study its construction, I'm not sure why this might be (i.e., where air could get trapped)... but it's just my experience.

Oh... and another interesting thing: today, after bleeding the calipers, I remembered to do the MC (which I think is actually supposed to be done first, especially after introducing air into the system at the reservoir like I did through negligence ). So I bled it and got significant air out. Decided to do all the calipers again and made sure I pumped the brakes (in addition to pressure feeding) at each caliper. Got a little more air out. And then once again at the MC... and I got more air there not while pressure feeding, but when pumping the brake pedal again. At this point, I'm not sure where all that air might be that I introduced at the reservoir. Gone, I hope, but I'm not sure. Until I get it on the road again, I just don't know. But if it's not satisfactory, I'll make sure I activate the ABS (if I can) and rebleed everything.

I could kick myself for letting air in the reservoir. I knew I had to avoid that, I screwed up anyway.

Ed Scherer

Nicole, this is really sad to hear. I know how much you enjoy your car when it's running right and now you must really be dejected after trying to make a nice enhancement and opening up this can of worms.

Especially rough when some of the best people have tried so hard to figure it out to no avail.

I'll certainly pass along any information and experiences I can turn up, but I suspect you might have an issue that's harder to solve than the one I had back in 2002. But I'm not sure how my current situation will turn out. It might be similar to yours, in which case I might wind up going through the same diagnostic techniques and trial-and-error procedures to fix it.

Good luck with yours. Are there any planned next steps with your car? And are you driving it to the DFW OCIC?

Nicole

And vice versa!

Bill and I are still trying to figure out what would make sense to try next.

No way! I'd rather fly United...

Are you planning to be there?

Ed Scherer

Oh yeah, wouldn't miss it. Spongy brakes or not.

I desperately want to get my A/C working by then, though (black/black car and all that...). All the parts are lined up on my workbench. Now all I need is time and some patience.

Nicole

Hope you can get it all done before the big event!

Ed Scherer

Yeah, we'll see.

BTW, this evening, I was a bit discouraged about how slow my progress has been on a number of shark-related tasks that I really wanted to get done before the OCIC in DFW. So I decided to take the car down off the jack stands and take it for a spin, mostly to see how the brakes would perform after the new pads and hoses, and... after I injected so damn much air in the brake system.

It was a bit scary at first, but the brakes got lots better rather quickly. Some interesting things to share:

• I've got new Hawk HP Plus pads at all four corners. With the proper "damping plates" (or whatever they're called).
• When I installed the front pads, I noticed that they were bigger than the previous pads (Mintex). Mostly, the outside part extends all the way to the edge of the rotor. I'm not sure if this is a manufacturing defect or what, but since my rotors already had some wear, it was a matter of some concern. In particular, I was wondering if the new pads would ride the lip on the rotor and not get any bite. I actually think this was happening at first. I probably should have ground down that edge of the pads or maybe started with new rotors, but I didn't.
• As I was going through Hawk's burnishing procedure, the brakes got pretty darn good rather quickly.

I still believe that I have more brake pedal travel than I had before I started on this. If I have time before the OCIC, I'll go through the bleed procedure one more time, now that I've driven the car a bit and activated the ABS a few times.

At this point, I think the brakes are performing just great, except the pedal is just not as firm as I think it should be.

BTW, the burnishing procedure is rather fun. The brakes were so damn hot that I could smell them as I was driving. I was using a rarely-used, really rural oval "circuit" road near our house that's mostly surrounded by cornfields. I was wondering if it was a bit risky, as it's animal city around here. Sure enough, I encountered a doe and her two fawns at one point. Anyway, the car is still outside on the driveway, where I was letting it cool off (and leave the hot new brake stink outside) before bringing it back into the garage so I can start on the A/C overhaul.

blown 87

I have one, it is helpful on some systems but is a real pain to use.

Bill Ball

Yeah, I got one and we tried it on Nicole's car. It seemed to work OK, but produced no bubbles.

dr bob

I need some experiment time on my car with a real vacuum pump attached to the top of the reservoir. See if I can degas the system that way. I'm concerned that air will be drawn past the MC rear cups. Otherwise we should be able to completely evacuate the air from the system with no fluid in it, and draw fluid in from the caliper ends of each line or even from the MC bleeder port.

Leon Speed

I am watching this thread with interest, because my brake pedal travel is long too and feels a little soft since refurbisching the brake system and essentially letting it sit dry for a few days. Maybe a silly question, but if you use a pressure bleeder, wouldn't it make sense to lift the brake pedal al the way and hold it there while filling & bleeding?

Btw regarding Nicole's issue: when you are sure there's no air in the system after xx bleeds, logic states that someting is giving and not supplying enough brake fluid to the pistons. Maybe the calipers, maybe the master cylinder.

Bill Ball

We're not sure there is no air in the system.