Just picked up the car from a specialist where I had a full fluid flush for the brakes, clutch and pdas systems.

The brake pedal is now quite a bit lower than it was and very soft. Alarmingly soft. It was rock solid when I went in.

Is this just a bad bleed with air in the system or is there something more sinister that I should be thinking about?

I've already called back and arranged to have a re-bleed, but wanted to check with the experts to be sure I've covered all the bases.

Thanks,
Dave

 

Same happened with mine. I had the shop rebleed everything- no air bubbles found and still a spongy pedal. THey said it might be worn seals/or crap trapped on a seal in the master cylinder ($650 for the part) but they suggested that I cycle the pressure pump before commiting to the new part (BTW neither they nor I could find a rebuild kit for the master).

Try to clear the master cylinder's throat by:

a) turning the key to the click that makes the pump buzz
b) pumping the brake until the pump clicks on again. try different levels of pumping and standing on the pedal, i.e. halfway, quarter, etc.

It took about 30 minutes of this to get it to burp. Then it was back to normal.

 

colo964,

Thanks! I've just tried your procedure and after about 15 minutes the pedal is back to normal.

I love this place!

Cheers,
Dave

 

It's been a couple of weeks and I've been traveling and working so not driving the car much. While the brakes are definitely much, much better than when I picked the car up the pedal is still a bit lower than it used to be and a bit softer. Though, it can be pumped up to the full height that it was when it went in.

I had the system filled with "cheap" fluid. Could this be the difference?

 

The cheap fluid is not going to make the pedal soft, just might boil on the track. The cheap fluid is still a fluid and will not compress any different. You either still have air in the system or a leaking seal in the master cylinder. A leaking seal will allow you to pump the peddle up to full height and then while holding pressure on the peddle it slowly sinks back down. Air in the system gives you a spongy peddle and a lower peddle since the air is compressing. I bleed / flush my brakes before every track event. Sometimes I have to go back around if I don’t like the feel. Hope this helps.

 

Did they bleed BOTH nipples on the calipers? (There are 2 on each caliper I believe)

 

Dave,
You do not mention if they bled the hydraulic accumulator and brake booster. The hydraulic pump has nothing to do with the master cylinder. There is no direct pressure/fluid link between the MC and the brake booster.
The hydraulic pump pressurises the accumulator which in turn provides pressurised fluid to the brake booster onto which the MC is mounted. There is a mechanical link between the booster and the MC to provide the power assist.
Using the hydraulic pump refills the accumulator, fills the brake booster and raises the pedal, but does not remove the air.
If the boost cct is not bled properly the pedal will be low and feel soft and using the pump only provides a temporary fix.
A lot of people believe that if you bleed the PDAS cct you also bleed the accumulator/ brake booster cct, this is not true. There is a bleed nipple on the accumulator.
My first recommendation would be to ensure the accumulator and brake booster are bled again and all air removed. You must ensure the fluid level is maintained throughout the process otherwise you are wasting your time. You must ensure that the far right chamber on the brake fluid reservoir remains full at all times during this process. If the fluid is sucked down and it's emptied, air follows really quickly. The accumulator holds around 300cc of fluid.
Ciao,
Adrian.

 

I don't know if they bled the hydraulic accumulator and brake booster. I was assuming (I know, never assume!) that they were bleeding the entire hydraulic system. That's what I asked for. I paid for two procedures: 1) Flush Contaminated Brake Fluid and 2) Bleed Clutch AWD system with bosch hammer.

I'm going to schedule a re-bleed and want to be sure I have the correct procedure when I go back.

I believe what needs to be done is:

Bleed Brakes

There are four brakes, each with two bleed nipples resulting in eight bleeds.

Bleed Clutch

There is a clutch slave cylinder bleed nipple accessed via the left rear wheel area.

Bleed Pressure Accumulator
Located in front trunk.

Bleed Transvers and Longitudinal Tracktion Control Systems
Bleed transverse and longitudinal locks with Hammer controling lock.

This is a total of twelve seperate bleeds.

Please correct me if I am mistaken or have left anything out.

Finally, thanks very much for the input. The time, effort and information provided by the individuals on this forum is extrodinary. I am very much in your collective debt and very much appreciate all that has been given and all that I have learned. My Porsche ownership would surely be a whole different experience without this valuable resource. Really, thanks very much.

Cheers,
Dave

 

Just back from the specialist where we re-bled the brakes and clutch slave cylinder. All's well again. The brake pedal is back up where I'm used to it and nice and firm. I had been taking these brakes for granted. What a difference!

As to the cause, it turns out his bleed machine broke down. It's an all-in-one unit that provides pressure and fresh fluid through the fill cap and suction at the bleed nipples. It was unusable on the next bleed he did after my car so must have been on its way out during my bleed.

We did not re-bleed the transvers and longitudinal locks, nor the accumulator as these are bled using the onboard hydraulic pump. I expect this was a reasonable approach.

So, nine re-bleeds and a firm brake pedal again.

Thanks again for the advice.

Cheers,
Dave

 

your fluid should be pretty clean by now!