StratfordShark

Brake job now finished apart from bleeding, so about to use the Motive Power Bleeder for first time.

Still have rear wheels on stands which will save some time, and have checked that the rear caliper bleeder nuts open OK.

Couple of questions:

- with the 4 pot calipers do you always bleed the inner nipple first?

- the instructions for the bleeder are very straightforward apart from the end. It says that if there is fluid left in the bottle (presumably there must be, or you'd be filling system with air!) then you have to tip fluid away from the tube, then bleed nearest caliper to master cylinder till reservoir level has fallen to max.

- my S4 is RHD, so I'm planning to bleed in order MC, LR, RR, LF, RF. Should you bleed MC again at the end?

Is this what people here are doing, or is it OK to just depressurize the power bleeder and remove from fluid reservoir, taking care not to spill fluid in the connecting tube?

Thanks for any advice - I'm really looking forward to driving the 928 again!

the flyin' scotsman

Stratford............while 'convention' typically starts the bleeding process at the furthest away caliper I believe Walley P found a Porsche article recently which described starting at the MC then nearest to furthest caliper. I stayed with convention and it worked fine.

One great tip I learned from the 'List on the power bleeder was to add a small piece of tubing (1 1/2") to the cap that screws on the MC. Once your done bleeding the system and release the pressure on the bleeder the added piece of tubing brings the brake fluid level in the MC down to the correct max fill level.

RyanPerrella

Once you have one of those motive power bleeders flushing the lines is so easy. It may take you longer the first time, but it sure beats pumping on the brake pedal or using a mityvac.

FlyingDog

Yes.Using the power bleeder will overfill the reservoir. The purpose of tilting the bottle is to empty the power bleeder hose and put some air in the reservoir to get the correct fluid level.That's what I do. Takes minimal extra effort and wouldn't hurt.I try to keep over half of the tube filled with air so that depressurizing the system at any point will suck most or all fluid back into the power bleeder. Always depressurize the bottle, not the reservoir.

StratfordShark

Sorry but I can't visualize what's meant by this, but it's clearly a great tip if it leaves the MC at correct level!

Where does the extra tubing go as the cap just has the line running to the power bleeder bottle?

StratfordShark

Have just been testing the connections when pressurized, and it strikes me that it's quite awkward to screw on the cap since the power bleeder line is clamped at both ends. It seems to require rotating the power bleeder bottle with the cap. I'm anxious about doing this at the end of the procedure when the bottle still has brake fluid in it!

StratfordShark

Hmm, well it seems using the power bleeder is moot, as I have a leak somewhere in the master cylinder. When I pressurize the power bleeder the pressure doesn't hold, and if I get pump to around 10 psi I can hear a hissing from around the MC.

So I need a new MC (though it was last changed in April 04), but in the meantime is it OK to bleed the brakes conventionally rather than with power bleeder?

JHowell37

10 PSI is a lot of pressure to place on the master cylinder reservoir. The most I've placed on mine is about 5 PSI and that's more then enough to move the fluid through. There's a cheapie bleeder system at most parts stores that's little more then a bottle with screw top, a hose attachment on the cap, and a small hose that goes in the bottle. I used it to bleed my '96 explorer the other day. The '96 and '97 explorers are notorious for having a brake system that is very difficult to properly bleed but I was able to get mine done with minimal headache. Simply hook the hose to the bleed screw, open the bleeder, get in, pump the brakes several times, when you're satisfied close the screw and go to the next wheel. Very easy.

the flyin' scotsman

10 psi is all you should need, max!

the flyin' scotsman

On the inside of the cap so it sits in the MC.........I just press fitted the tubing into the cap.

hacker-pschorr

Could be the blue hose - might have blown it loose with the power bleeder.

the flyin' scotsman

From what I've read that could be an issue but I believe the blue hose was deleted with the auto option; at least it was with mine.

Not to be rude or embarrassing HP; just keeping Stratford straight; he's English you know.

StratfordShark

LOL!

I don't think I've blown anything off. The pressure wouldn't hold at just a few psi - pumping it up to 10 provoked the hissing noise.

Could be it's just leaking around the threads of the MC bleeder screw. I don't think it's the grommet between reservoir and MC as level is fine and nothing wet around there. I'll squirt some soapy water around the MC bleeder tomorrow and see if that reveals a leak around there.

When I fitted new front rotors and pads I got some air in the sytem when I was trying to get fluid out the reservoir. The pedal sank lower than usual so I may have damaged the in the MC by moving into 'uncharted territory' with corrosion/rust damaging the seal. Or could be the leak has always been there but slow enough not to notice anything dramatic.

Anyway I can't use the power bleeder even at 5 psi with the leak so I think I'll have to bleed using the pedal method and get it safe to drive till I can organise replacement of the MC if that's what's needed.

hacker-pschorr

WTH do I know about automatics???

Yea yea yea, read the sig next time.......

What about the seal between the reservoir and the master?

hacker-pschorr

I just had what an alcoholic would call a moment of clarity. My power bleeder was leaking around the cap to the bleeder (with no fluid squirting out). I ended up taking the gromet out of the reservoir cap and installing it into the cap of the bleeder. Worked like a charm.