I spent 2 hours trying to get some fluid from the right rear caliper with the Motive pressure bleeder set at 20 lbs. First I withdrew as much from the master reservoir with a turkey baster as I could, then refilled to close to top of threaded neck with new DOT 4, then pressurized and started at right rear caliper. Very little came out (2009 base). So stopped the procedure, buttoned everything back up, test drove car (just changed plugs this am also), and pedal height was HIGHER than before, and pedal was very hard, like it should be. I just didn't flush much, about 1/10th of one quart.

So over to the 997.1, and did all four corners no problem. Nice high predal, very hard, good deal. Staring back at the 957, decided to post situation here for comments.

I have the workshop manual for the 997.1, but not for the 957, so don't know if ABS has to be set a certain way with PWIS or something with the 957. I at one point had the bleeder screw 2 turns out of the caliper, and the fluid was just oozing out very slowly into my containment hose.

 

There isn't anything normal with the ABS that would cause slow flow. How vicious was the fluid coming out? Notably thicker than new brake fluid? I've heard of badly neglected brake fluid being water logged and turning into a sort of gel. If that's the case - I think a flush is in order - removing the brake caliper from the line and making sure the line flows freely. If it does - I'd be suspicious of some corrosion in the brake caliper, perhaps back-flushing it might be revealing (while disconnected from the brake system.)

BTW - AFAIK there is no workshop manual available for the 957.. I think your best bet might be ALLDataDIY - a subscription is inexpensive, and generally the data is fairly complete.

 

I saw this post yesterday-

https://rennlist.com/forums/cayenne-...l#post16008307

Got me to wondering....?

Fluid that came out was clear and thin.

Going to try a little manual flushing of the same caliper using brake pedal with 4 by 4 block under the pedal for the wife as she operates it, engine off, ignition off.

 

How many miles on your Cayenne? One of the reasons I replace rubber brake lines with stainless steel on any car I purchase is because the rubber lines swell internally restricting flow. Lots of other reasons too - Teflon lining so lines are impervious to the fluid and last the life of the car, they're stronger so a tire gator is less likely to completely sever the line on a fluke, pedal feel is better as the line doesn't expand under pressure, etc

ECS Tuning has a good set and what's on my CTTS along with Motul RBF 600 in it that gets flushed annually.

 

Has 130K miles. Actually has a hard firm pedal action, but want to flush out the fluid. Have appointment in Midlothian Porsche to flush coolant, since all other fluids have been changed about 20K miles ago. On the power steering, used the factory fluid, evacuate reservoir, refill, run it, do it again, about 4 times. Since it is never outside unless being driven (retired now), clear coat and headlamp xenon lenses look very good still. It is a great truck.

 

I have the Motive as well, and use it on all my cars. There are many different ways to use them, based on convenience and user preference.

I always do what you do and don't actually fill the bleeder with brake fluid. Just air stays in there, and the brake fluid goes in the reservoir. Slightly less convenient maybe, until it comes time to clean the bleeder. So that's my preference there.

The other thing I have learned to do is to set it up pressurized (BTW, I never go as high as 20 psi. Usually 10 is plenty) and go to each caliper, loosening to let it flow and observe. And then, I'll have a helper pump the brakes as I tell them to, with a block of wood under the brake pedal as you'd normally do when doing a non-pressurized flush.

What I often observe is that with each pump, some dark debris / dark fluid will be released that was not coming out just with the pressurized flow but no pumping. So I'm convinced that the extra pressure from pumping will cause some turbulence to get the junk / sediment up from wherever it may have settled. Vs. the regular pressurized flow was just not getting it done by itself.

In your case, with an apparent blockage, I'd do the exact same thing. Maybe the pump is all that is needed to break it free so the regular pressurized flow will do the rest.

 

On the 957 I first removed as much old fluid with a turkey baster as I could and refilled (to the brim) with DOT4. The I tried pressure only. You know, first you do a dry air leak test with your Motive cap fitted, which I did, per the instructions in their video. Since it was holding so well, I undid the right rear bleeder some and just got a tiny dribble out. This is weird I thought. So I let that situation just play out by itself for over an hour, since I had overfilled anyway. About a 10th of a quart was the final score. Secured everything, and pedal was higher (about right) and firm. At least no air was introduced.

Then I moved over to the 997 and did a normal 2 quart flush starting with initial air leak checking again. Then I put DOT4 in the container and flushed away. It came out of those calipers really well, so that job took 15 minutes maybe (not including cleanup).

I'll report back with the manual flush on the 957.

 

So you do a low pressure flush at 10 lbs and at the same time pump the brake pedal with the assistant ? I guess that would make sense, and looked to be what one poster read in the service procedure for the Cayenne (old post I referenced above).

To play it safe, are you coordinating the bleeder valve securing before the assistant releases the brake pedal ?

Or do you have the bleeder valve dumping into a local container via rubber hose ?

 

Expanding on what I said above,
reservoir full and pressurized to about 10 psi. I would not call that low pressure, but that's just me, maybe.
I am down at the caliper. Clear vinyl hose running from bleed screw to a clear gatorade bottle with a hole drilled in the orange cap, if those details help.
I open the bleed screw, and let the fluid flow, observing, watching things get clear, hopefully.

Then, for example, to see if the additional pump method gets more out, ...
I'll close the bleed screw.
Make sure the reservoir is filled.
Put a 2x4 under the brake pedal and ask my helper to wait my command.
Back at the caliper I say to press on the brake pedal, just as when doing a regular brake bleed without a pressure bleeder.
I control the flow by cracking open the bleed screw, and watch for any new stuff that might come out. Hopefully nothing.
The coordination of me at the bleed screw and the person on the brakes is done just as if doing a non-pressurized flush. I'm not sure if this is needed - e.g., with the pressure, maybe closing and opening the bleed screw on each pump is not required, but I just do it.

So I guess to summarize, it's like I set up and do a pressure flush. But part way through, while pressure is still applied, do a regular synchronized pump and bleed.

For me, I have found it sometimes gets a little more stuff out. But for you, with perhaps a blockage of some sort, I think it might be even more helpful. The pressure when stepping on the pedal is far greater than that from the pressure bleeder.

 

Thanks, I will try that.

 

You can try doing 10-15 hard abs stops (50-0), to get the fluid moving around in the system, and hopefully to clear the flow to rear calipers. Then probably after the brakes cool off or the next day, use about a 1 liter of fluid to replace it in all calipers.

If I recall correctly, there are 2 bleeder screws in each caliper. Did both of them had weak flow at the rear? Pressure bleeder alone doesn't provide enough flow, that's why I use 10psi + brake pedal process like oldskewel.

 

When I use my pressure bleeder I do a similar setup:
- clean fluid in M/C reservoir
- clear tube on caliber bleed screw
- low pressure (10#) on the pressure bleeder (pushing air only into the M/C reservoir)

In my experience, the fluid flow with just this setup is not super fast. So I'll leave the screw open and give the brake pedal 10 pumps or so to speed the flush along. I do not use a helper, as the 10psi of pressure keeps bubbles from coming back into the calipers.

I also take a small shot glass sample of brake fluid and use a brake fluid tester to make sure I've got all the old fluid out. Sometimes you can't tell how good the fluid is based on color alone. Once I'm getting readings that match what I'm putting in (usually less than 1% moisture) and have no bubbles, I call that corner good.

Make sure you keep track of how much fluid is in the M/C reservoir using this method -- it's easy to run out and introduce air in the system -- BTDT.