Finally had a day off to work on my rear brakes. Needed a new caliper for the rear right. Installed it and tried bleeding the brakes. With bleeder screw closed, had my helper push brake pedal to the floor. Loosened bleeder screw. Heard air come out. No fluid. Closed screw. Helper released pressure on brake pedal. Repeat the process and hear air again but no fluid. Repeat, a tiny bit of fluid. Repeat, no fluid. Repeat, tiny bit of fluid. Stop.

Now I just went into the car and pressed the brakes. minimal resistance. Pumped a little bit and couldn't get any more resistance. Started the engine and pressed the brakes, no resistance at all.

Is it just a matter of continuing the process until we start getting some substantial amount of fluid being forced out?

Forgot to mention, car is a 87 560 sel.

The master cylinder reservoir has a front and rear chamber. Check that there is brake fluid in the rear chamber. It's best to use a pressure bleeder when bleeding the brakes, but your method of pumping & releasing the brake pedal will work too. Be sure to close the bleeder screw when your assistant is letting up on the brake pedal so you don't suck more air into the system. Bleed all four calipers in this order ... RR, LR, RF and LF.

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Fred Hoelzle

I didn't know there was a rear reservoir. It is empty. How can I fill it?

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The Dude

1987 560 SEL

Got it. Just had to wiggle the reservoir a little bit. Rear right now functioning. Going to do the rotor and pads on the left. Thanks for the tip.

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The Dude

1987 560 SEL

I've now finished the left side and bled the caliper. After taking the car for a short and slow test drive, the brake pedal still has a soft feel. While I was bleeding the right side the fluid that came through my reman caliper was really dirty. Could this be a cause? Should I just keep bleeding the thing till I see some nice fresh fluid? My stopping power is decent but not up to the standard. Could only changing the right side caliper be the cause? Any thoughts on this are welcomed as I have the day off tomorrow and can spend some time in the garage.

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The Dude

1987 560 SEL

let me ask this....did you keep adding fluid during this process. Also you have to bleed all 4 calipers if you dump fluid for 1 anyway...sounds to me like this wasn't done right.....I'd be careful....

Yes I did keep adding. Only problem was that I did not know about the division in the MC reserve tank for front and rear and ran the rear portion very low if not empty as the front portion was still at the max mark. I was not sure if I had to bleed the front as the level in the reservoir did not change for the front. If I were to start the entire process over again, what should I look for?

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The Dude

1987 560 SEL

I'd go ahead and rebleed the entire set...you need to fill the reservoir up to damn near the tip top to get the fluid into the rear chamber. It sounds to me as though you still have some residual air in the system, probably some trapped in the ABS module. A suggestion would be to go and get DOT 4 Superblue fluid and a turkey baster. Use the baster to remove as much of the current fluid as possible from the reservoir (don't use the baster for food after this...). Fill the reservoir with Superblue. Bleed the right rear first. The reason to use the Superblue will become evident as you can easily tell when the new fluid comes through. Just make sure you keep the reservoir full as you (or your assistant) pumps the brakes. Tighten the nut on the right rear, refill the reservoir, and do the left rear. Same situation for the refills. Then do the right front, and finally the left front. A full rebleed should deal with the problem. Next year, when you do the bleed again (you should do it once a year, esp. if you live in a wet environment), you can use DOT 4 Supergold (same reason-- the color change is obvious).

Best of luck!

Well, I did the full bleed..twice. Went through about a 1 litre of dot 4 brake fluid. The brakes still felt soft after the first bleed so I did them again. No air bubbles coming through the system but they still feel soft. When the ignition is off the are extremely hard. Then when I start the car the pedal droops down not quite to the floor. On my test run I stopped fairly aggressively and even got a little chirp from the tire. It just seems as though the first few inches aren't giving me much stopping power. When I pump them the get a little more firm. Pads up front are almost toast. With new ones on the back and dead ones on the front, could this be a cause?

On another note, I was feeling adventurous today and changed my valve cover gaskets. Though things were great but on the test run a major oil leak leaving a trail up and down my street. Back corners on both sides were tucked under the cover. Oil everywhere. I guess if I am bleeding brakes twice why not the valve covers twice. Got it right the second time but have noticed one thing. The economy gauge or fuel consumption is pinned. Stays there even when I turn off the vehicle. Anybody have an idea of what I messed up?

Any thoughts on this would be appreciated.

Noticed some white smoke from tailpipe today. Everything is breaking down at once. On a positive note, my guides for the timing chain looked to be holding up ok. Phew.

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The Dude

1987 560 SEL

On the brake issue, it seems as though you've done everything you can to this point. Yes, I think you should replace the front pads, though I don't think that's a reason for a soft pedal. I still think you must have gotten air in there sometime during your initial attempts at bleeding. I have heard that the ABS system can trap air inside the box, so I would venture to say that a pressure bleed might be needed-- and I'd also suggest breaking down and having a pro look at it.

On the economy gauge, I'd lay money you inadvertently knocked the vacuum line off its connector (or broke a connector) when you were fiddling with the valve cover gaskets. Check the connection at the false firewall right in front of the brake cylinder. There is a three-way connector there, and I think this is the feed into the gauge (the gauge simply reflects engine vacuum). I think the line that goes through the true firewall into the gauge is grey plastic with a white stripe-- could be mistaken though. Another connection to check is at the rear of the passenger side intake plenum, just inboard of the valve cover.

As to the white smoke-- check to see if the overflow tank for the coolant system is getting pressurized-- you could have a head gasket issue developing.... Also check the dipstick and look at the oil-- I had the dreaded mayonnaise when my head gasket went.

I am having the same problem with the brake pedal and I used a power bleeder on my 560SEL. I also made sure that the rear reservoir chamber was full. All fluid coming out of the calipers is the new stuff with no bubbles.
There has got to be something fundamental that we are missing.

In some posts I read, I have heard that it could be the master cylinder relating to the brake problem. only thing is that the brakes worked normal before I replaced the caliper. Also the thought of a hard brake before turning on the vehicle has me stumped.

As for the vacuum line, this is what I suspected as I disconnected it from inside the(beside the fuse box)firewall and heard air released. I had to move it to get the drivers side valve cover off. Seems as though I replaced it properly.

Coolant level is ok. I heard the white smoke might be from a transmission modulator as well???

I think it is safe to drive the vehicle with the soft brakes but would like to get the problem rectified sooner than later.

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The Dude

1987 560 SEL

It's possible that you damaged the master cylinder during the manual bleeding process by having the piston go beyond its normal travel range. If that's the case then you would need to rebuild/replace the master cylinder. It may be a good idea to have a local indie diagnose your brake system problem. It's not worth the risk driving with a faulty braking system.

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Fred Hoelzle

Is there any way to check the master cylinder?

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The Dude

1987 560 SEL