DonS

Replaced brake lines with stainless steel then went to bleed the system using power bleeder. I started with the master cylinder, no problem. Went to passenger rear, nothing. No flow at all, like no pressure. I checked the bleeder and it was at 13 psi. I went to driver's rear, same thing, no flow when I opened the valve. Went to passenger front, normal bleed. Driver's side, normal bleed.

So why won't the rears bleed? What'd I mess up? Proportional valve?

Ed Scherer

Stuck check valve in Speed Bleeders perhaps?

DonS

The bleeder seems to work correctly. I can disconnect the collection reservoir from the passenger rear (no flow), hook it up to the passenger front, open the valve and get a nice flow. It's just the rears that aren't bleeding. The power bleeder is holding at 13 psi. The pedal is rock hard.

What's going on?

928Myles

Rear bias valve stuck?
Twist / kink in rear line?
Plastic plug left in end of new line?

Myles

worf928

Bleeders have crud in them? Turn them all they way out - put a catch pan under caliper - and see if you get flow (with bleeder pressurized, of course.)

GlenL

These aren't speed bleeders, are they?

Remove and clean the bleeders. Replace them and leave one well open with hose/bottle attached and then pump the brakes. That should get it going. Repeat on the other side and then do a quality bleed.

Mrmerlin

FWIW bleeding procedure for the brakes is LF RF LR RR.

To get things moving remove the pressure from the bleed system,
step on the brakes a few times,
then go open each bleeder one at a time till you get flow.

Once this is done then attach the Motive bleeder to the tank.

NOTE follow above bleeding sequence
NOTE I suggest to use 10 psi or less as the possibility exists of blowing off the tank,
this will make a huge mess

DonS

I did a visual and flow check on each line before installing and used same path as the old ones. Checked all the hard lines and no twists or kinks. PET illustration 604-05 shows all the hard lines individually going directly to the master cylinder so is the rear bias valve inside the master cylinder? How do I unstick it?

DonS

Will give the suggestions a go this morning and report back. Thanks everyone.

DonS

Worf and Glen called it - dirty bleeders. After putting a pan under the caliper I just removed each one and had a good flow. Finished the job in minutes. Both were missing the protective caps and being vertically oriented they were full of crud. Cleaned with brake cleaner and replace the caps.

Not speed bleeders, Glen. Just the regular ones. Sorry to mis-interpret. Thanks for the replies, everyone.

69gaugeman

Really? I haven't read the WSM for the 928, but I was always was taught and performed, bleeding from the farthest point to the closest point. I will have to go and look in the manuals. Not questioning it's validity, just want to verify the source.

It's amazing how hard that crud can get. I've had to drill it out before as even brake pressure wouldn't dislodge it.

CYTH

Actually it the procedure is the enact opposite of the of the order mentioned. RR LR RF LF (the last closest to the reservoir)

I ironically just replaced my original rubber lines with SS units yesterday. Performed the exact order (as i always have performed on varied cars. I was taught this sequence while working at a restoration shop years ago)

Great pedal. No issues.

If your bleeders where dirty/ clogged the rubber caps were missing.

Also remember (I assume this was performed) each wheel has two bleeders. (fixed pot calipers will usually have one or two ...upper and lower... per side of rotor as opposed to a more common sliding caliper.

Mrmerlin

The WSM references the reversed bleeding procedure LF RF LR RR

jon928se

While I religiously observe the WSM procedure (perhaps due to superstition) On an S4 at least it can't matter which rear wheel you do first as there is only one brake line to the rear of the car to the Tee piece that feeds both wheels.

I suspect that left or right first at the front does not matter either as both are fed from separate ports off the same part of the M/C.

What does matter is Front or Rear first as these are connected to different parts and "pistons" in the MC. Not forgetting that first thing to do is bleed the M/C.

Dave928S

Every car I've bled brakes on I've always started at the master cylinder and worked my way down the lines ... and always done that rotation at least twice. and usually three times. A quick bleed to get the bulk of air out, a bleed to get small bubbles and flush old fluid out, and then a final go around to ensure no bubbles left.