A new brake bleeding thread ... what did I do now?

[BodhiBenz1987]

... So after a bit of a hiatus due to health issues, I finally got my brake job on the 124 done, including all new rear hard lines. Almost. I went to bleed it using my Motive power bleeder and new MB brake fluid and here's what's happening. I started at the back right and when I open the bleeder, a bit of fluid comes out, then a frothstorm of bubbly fluid ... which I expected of course ... but the froth just keeps on coming. Then nothing comes out at all. I go look at the bleeder and it's lost all its pressure. Pump it back up and try again, same deal. Club soda, then loses pressure. I've used the Motive bleeder several times with no problem ... bleeding is a breeze. This is the first time I've replaced the hard lines though ... should there really be that kind of air coming out for so long or did I mess something up? I.e., a kink in the tube or a leak? I can't find a kink and I don't see fluid coming out anywhere. I had to rush off to work so I had to drop everything, but I'll inspect the bleeder unit again when I get home. Usually I pump it up to 15 PSI and it holds that while I bleed. Thoughts?

[BenzGirl]

Originally Posted by BodhiBenz1987

... So after a bit of a hiatus due to health issues, I finally got my brake job on the 124 done, including all new rear hard lines. Almost. I went to bleed it using my Motive power bleeder and new MB brake fluid and here's what's happening. I started at the back right and when I open the bleeder, a bit of fluid comes out, then a frothstorm of bubbly fluid ... which I expected of course ... but the froth just keeps on coming. Then nothing comes out at all. I go look at the bleeder and it's lost all its pressure. Pump it back up and try again, same deal. Club soda, then loses pressure. I've used the Motive bleeder several times with no problem ... bleeding is a breeze. This is the first time I've replaced the hard lines though ... should there really be that kind of air coming out for so long or did I mess something up? I.e., a kink in the tube or a leak? I can't find a kink and I don't see fluid coming out anywhere. I had to rush off to work so I had to drop everything, but I'll inspect the bleeder unit again when I get home. Usually I pump it up to 15 PSI and it holds that while I bleed. Thoughts?

Sounds like you have allowed the rear section of the master cylinder's fluid reservoir to run dry. If you don't allready know the reservoir is seperated into two sections and the fluid needs to flow from the front section over the divider and into the rear section. If the level of the front section is not high enough none will flow over the divider into the rear section and you will run it dry. Sounds like you've pushed out both the old fluid and any remaining fluid in the rear section!

[BodhiBenz1987]

Originally Posted by BenzGirl

Sounds like you have allowed the rear section of the master cylinder's fluid reservoir to run dry. If you don't allready know the reservoir is seperated into two sections and the fluid needs to flow from the front section over the divider and into the rear section. If the level of the front section is not high enough none will flow over the divider into the rear section and you will run it dry. Sounds like you've pushed out both the old fluid and any remaining fluid in the rear section!

The bleeder fills up the front section of the reservoir quite full, though, and I'm pretty sure it's flowing over. I'll give it an extra look and try pouring in fluid by hand to make sure it's flowing back there. It looked full, but since the reservoir is a bit opaque I could definitely be wrong.

[BenzGirl]

Originally Posted by BodhiBenz1987

The bleeder fills up the front section of the reservoir quite full, though, and I'm pretty sure it's flowing over. I'll give it an extra look and try pouring in fluid by hand to make sure it's flowing back there. It looked full, but since the reservoir is a bit opaque I could definitely be wrong.

Good luck! I use a flashlight behind the reservoir to make it easier keep an eye on the level! It is hard to see the clear new fluid level in an old dirty or stained reservoir.

[Biodiesel300TD]

When I've use my MityVac for bleeding brakes I always get bubbles. When you break open the bleeder valve and suck on it with a device it pulls bubbles from around the bleeder and not just fluid. Try having an assistant pump the brakes and drain the bleeder into a container the old fashion way and see if you still get bubbles.

[BodhiBenz1987]

Originally Posted by Biodiesel300TD

When I've use my MityVac for bleeding brakes I always get bubbles. When you break open the bleeder valve and suck on it with a device it pulls bubbles from around the bleeder and not just fluid. Try having an assistant pump the brakes and drain the bleeder into a container the old fashion way and see if you still get bubbles.

The bleeder I'm using is a pressure bleeder so it just pushes fluid out rather than sucking, so I don't think the air could be sucked in around the screw. Guess if it wouldn't hurt to try it by hand and see if that works ... I don't have an assistant though. Maybe my brother in law will help.

[layback40]

Bodhi,
Expect to have to fill the reservoir several times as you have completely empty lines and calipers.
I wouldnt use 15 psi, too high, it will cause you to make soda!!
Best have a pint of fluid on hand. Slow & gentle is the trick to bleeding brakes.
Using your mity vac may give a better result. Just keep the back part of the reservoir full.

Good Luck !!

[BodhiBenz1987]

Originally Posted by layback40

Bodhi,
Expect to have to fill the reservoir several times as you have completely empty lines and calipers.
I wouldnt use 15 psi, too high, it will cause you to make soda!!
Best have a pint of fluid on hand. Slow & gentle is the trick to bleeding brakes.
Using your mity vac may give a better result. Just keep the back part of the reservoir full.

Good Luck !!

My bleeder is supposed to keep refilling the reservoir automatically (you fill the bleeding unit with fluid and it pushes it into the reservoir) but maybe it's just not working, or maybe it doesn't work right with ABS. I'll bet its not keeping the back of the reservoir full, in which case I maybe will have better luck doing it by hand. If I can find an assistant ...

[Matt L]

I would recommend against using the master cylinder as the pressure source for bleeding. Find out why your power bleeder isn't working. Perhaps it's leaking air from the pressurized chamber to the hose.

You're supposed to pressure bleed these things.

[aaa]

Fill the reservoir to the rim before you put the bleeder on, that pinhole between the two reservoirs is annoyingly at the very top.

[BodhiBenz1987]

Thanks for all the tips folks. I'll fiddle around when I get home (or tomorrow ... I won't be home until 2 a.m.) and will update with my findings.

[79Mercy]

Since this is being such a pain. Find a friend and do it the old fashion way. Open bleeder, press pedal to floor, close bleeder, and release pedal....... Keep the reservoir full and you should be good to go.

[toomany MBZ]

If you're losing fluid too and can't find it, it may be leaking into the booster, just a guess.

[vstech]

"the old fashioned way" is not a good practice with ABS, power bleeding is the best way to go.
if you are getting bubbles and air, it's due to air being in the bleeder, or air in the master cylinder.
when you wake up and log on, I bet you'll have no issues once the MC is full by hand, and the power bleeder is verified to have fluid in the reservoir.

[BodhiBenz1987]

Well, it turns out the rear of the master cylinder was indeed empty! BenzGirl got it on the first shot. It was hard to see because my MC is a big foggy, but when I shined the flashlight on it I could see it was fluidless. So I filled it up, but the pressure bleeder back on (I also tightened the hose clasp on the power bleeder) and everything worked! Aside from hitting my face on the underside of the car, it went smoothly from there. Thanks guys!

I'm still having a couple issues, though ... one being a chuff chuff chuff sound when the car is rolling slowly (goes away when the wheel is turned left) that I'm guess might be dust shield. The other is that the left front wheel gets hotter faster than the others and smells a bit burning. It doesn't really drag when I turn it by hand but it has me worried. That was the wheel that seized on me on the highway and almost caught fire, which is what prompted this brake job. I replaced the calipers, rotors, pads, hoses and wheel bearings, so i don't know what would still be wrong. Maybe I made the bearings too tight.