brake bleed question

[bmw art car]

so i replaced the mastercylinder.
the slave cylinder, rebuild the rear brake and the front caliper.
replaced some had lines and installed ss lines instead of the rubber lines.
when i bleed the brakes first there was no pedal.
then i got a power bleeder. and been bleeding for ages.
a tiny bit pedal now...
but when i press it it sound like someone harmonizes a note with a
harmonica 'hummmmmm'.
when i turn on the engine , the pedal goes straight down...
no brake whatsoever...
i replaced the booster pressure hose... still same result
i unbolted the master, in case i forgot the rubber gasket there...
nope its there...
but no pressure... any clues?

 

[Stefan]

I had almost the same issue a few years back.
If this not fall between short and long memory i remember doing the two bleeding screws on front calipers several times according to manual and also opposite
Suddenly it was working!!

Thats the best life "insurance life" job I done so far with my E9. Last week I almost (really almost) crashed into a Mini cooper with a mobile phone speaking driver!!!
Yes, I was diving to fast, but still using a mobile phone while driving makes you not 100% aware of the other vehicles.
I did not raise the "ugly finger" afterwards because I was driving like hell..

Good luck and keep on bleeding

 

[sfdon]

you don't mention HOW you bled your brakes...


Rear first right to left?

In front right to left?

In what order did you bleed the front calipers? There are 3 bleeder screws on each caliper-

 

[bmw art car]

you don't mention HOW you bled your brakes...


Rear first right to left?

In front right to left?

In what order did you bleed the front calipers? There are 3 bleeder screws on each caliper-

had the power bleeder connected
i started at the rear passenger tire
then the drive side rear tire
then the front right side and the left front side
on the front calipers i did the inside , the outside and then the top

i done that 3 or 4 times now. the pedal is a little stiffer
but still goes to the floor when i turn the engine on.
still the hamonica in the master cylinder.
i do tomorrow some more
somebody mentioned that the rear regulator thingy should be
bleed too (?)

 

[heroszeros]

i've just been bleeding by brakes too- yes the sequence is 1-right rear, 2 left rear, 3 right front, 4 left front.

for the front calipers, you should bleed the top first, then inside middle, then outside middle. also, there is another bleeder located underneath the car on the left side of the transmission. this was holding alot of air in my case, so i would try bleeding this if you have a soft pedal-

 

[bmw art car]

i've just been bleeding by brakes too- yes the sequence is 1-right rear, 2 left rear, 3 right front, 4 left front.

for the front calipers, you should bleed the top first, then inside middle, then outside middle. also, there is another bleeder located underneath the car on the left side of the transmission. this was holding alot of air in my case, so i would try bleeding this if you have a soft pedal-

are you talking about the clutch slave?

i also noticed , the front calipers seem to bleed alright, the rear however have barely more than a trickle coming through.
is that normal?

 

[HB Chris]

Did you replace the hoses in rear as well? That can cause the trickle you are experiencing.

 

[bmw art car]

Did you replace the hoses in rear as well? That can cause the trickle you are experiencing.

yes, i replaced all of them with ss lines.
i did some more testing on the front calipers, they looked kind of tight.
almost stuck. to confirm my suspicion, i took the brake bads on one side out
and with pressure from the power bleeder nothing happened.
should the pistons not come out at least some? the didn't budge a bit
and i was able to push the pads right back in.

 

[bmw art car]

i think i'll go with rebuild calipers
i saw autohaus AZ has them for a very good price

 

[61porsche]

Achy brakey brakes

A normal pressure bleeder works on 12-20 psi. Not enough to move pistons when the pedal can create 300psi or double that by mechanical leverage.

Sounds from the master- check that the hose grommet is seated completely. Sounds like it could be the rear.

Since there is little fluid from the rears, hoses changed; it's likely the master has closed off on the rear circuit thinking it's leaking. Too bad that the manual doesn't explain how to move the pistons at all. Maybe Google was off that day.

Try cracking the pipe to the fronts at the master while letting out a small amount of fluid manually without the bleeder and by operating the pedal.
Then check for fluid at the rear while slowly pressing the pedal so as not to dislodge the master dual circuit again.

The pressure bleeders sometimes don't work if there's a problem and some cars. Great for flushing though.

My personal observation on the brakes and sticking- rusty pins/ dirt. The pads aren't free to move or release. Cheap fix- new ones ( hardware- pins and springs) for cheap.$16/ all of them 3 months ago.

 

[bmw art car]

update

i cracked a bolt at the primary circuit. the one going to the front alone.
and moved the pedal. i closed that cicuit again.
the brakes are soft and i see a lot of up and down motion in the reservoir.
when i start pushing the pedal a bit and release again.

 

[61porsche]

The rise and fall ( of brake fluid)

Large fluid movement at the resevoir means air. Bleed. Sounds like you got the rear piston on the master cylinder open though!

Steady pressure on the pedal until you get pressure and bleed so you don't move the pistons in the master again. Once you get full pedal, then pump and bleed the last bits of air. Your pressure bleeder should work now.
Bleeding calipers- there a sequence. Three bleeders. The single bleeder side first. Opposite low, then high. That's what Don meant.

Clean the calipers where the pads ride with a detail ss brush while you're down there. If the pins show wear spots/ rusty; replace.

Good!

 

[bmw art car]

Large fluid movement at the resevoir means air. Bleed. Sounds like you got the rear piston on the master cylinder open though!

Steady pressure on the pedal until you get pressure and bleed so you don't move the pistons in the master again. Once you get full pedal, then pump and bleed the last bits of air. Your pressure bleeder should work now.
Bleeding calipers- there a sequence. Three bleeders. The single bleeder side first. Opposite low, then high. That's what Don meant.

Clean the calipers where the pads ride with a detail ss brush while you're down there. If the pins show wear spots/ rusty; replace.

Good!

i've been bleeding brakes for 5 hours almost, with no big results.
all i get in the back are like microscopic little tiny air bubbles. barely
noticeable. but i got hopes that it's going to work.
it's not much hope , though

 

[61porsche]

bled all over

Take apart the M/C. Check the seals. Or replace it.

 

[bmw art car]

Take apart the M/C. Check the seals. Or replace it.

I don't know how old the M/C was . but it had plugs in all openings and looked overall new. maybe i get a seal kit and see if i can mend it.

I just read that i can use a volvo M/C is that right?
and what model?

 

[61porsche]

master err.... cylinder

A kit would be fine. Measure the bore as there were 2 sizes. 22mm and 23mm. The boxes are usually marked on the end or I should say they once were.

Likely the return spring is shot; but since quality isn't what it should be sometimes it's assembled incorrectly, missing parts, etc. "It" happens.

I've heard about substitution; don't know any parts/ car numbers though. I'd find the BMW part.

The only thing like that that happened sometime ago was to use a US size kit vs. Metric 3/4 or 7/8". But that was because there were no kits at the time.( Porsche), wheel cylinders were $300 ea., and there were 6! Now they're back and $59/ea.

 

[bmw art car]

I looked through my 'lucky box' i got three clutch slave repair kits.
a master clutch repair kit. and a box ATE part # 03.0370-3723.2
looks like a master-cylinder kit. but i am not 100% if it's the right one
i will take the M/C off tomorrow.
any hints i got to look out for?

 

[John Buchtenkirch]

I’m going to take a really wild stab at this one only because I ran into very similar problems some 25 or 30 years ago. Is there even the slightest chance when rebuilding the calipers you got the sides reversed so that now the bleeder screws aren’t at the top of the calipers anymore ? It happened to a friend of mine on the rear end of a Volvo he was rebuilding --- couldn’t get a brake pedal for 3 days till I figured out what he did.

Another time years ago I was having a hard time getting a pedal on I think a Chevy truck ? I asked a mechanic friend for help and he asked me if I bench bleed the master cylinder. I had never heard of it so he had me mount the master in a vise and hold my fingers over the pressure ports and use my other hand to push a rod into the master till it was pressuring my fingers off the ports. After that happened I installed the master in a loaded up & dripping condition and to my surprise the brakes bleed OK and I had a good pedal ! I don’t claim to be a mechanic, just an old body man & welder but there’s a couple of long shots I did run into. GOOD LUCK ~ John Buchtenkirch

 

[61porsche]

repair m/c

The manual is pretty good on this part. Pay attention to the stop bolt and the sequence of the pistons.

Sometimes if there's light bore corrosion- VW brake hone used in a container with brake fluid. Other wise it's toast.

Rub the lucky box and shout schnell!

 

[bmw art car]

Thank you for the great advise
the calipers are installed the right way , i made sure of that.

However, i didn't bench bleed the master...and that might be my mistake
i see tomorrow when i take the thing out and see what's up
Maybe i blew out a gasket? or the return spring snapped?