[mness4]

I'm in the middle of replacing rotors and calipers. Because I would not be immediately replacing the old calipers with new ones (it's taking some time to get all of the old parts off and I'm painting the new calipers), the brake lines were left unattached. Some fluid drained out but seemed to stop with reservoir low but not empty. The next morning I saw that the reservoir had completely drained. When it comes time to bleed the system, I'm assuming I will have to do more than bleed the system at the calipers. Oddly, there is no procedure described in my Haynes manual for bleeding the master. I've heard before bleeding the calipers that I should do a manual bleed of the two green lines on the master, starting with the connector closest to the booster.

I will be bleeding the line with a vacuum kit. Can someone confirm that the above procedure is correct and the master bleed is necessary even with a vacuum bleed?


Thanks,
Mike

 

[jmkcc]

Not sure you will have any air pockets in the MC or not. If so I don;t think a vacuum bleeder will clear it but you can fabricate a MC bench bleeder by cutting a short brake line (just make sure you get the right size Euro flare fittings), attaching the two flare ends to the MC and bending the hose/tubing up and into the reservoir so the ends are submerged. Make sure the MC is level (may need to jack front or back of car) and slowly pump. Basically doing a bench bleed on the car.

I replace the MC and ABS unit so after bleeding MC, I connected pressure bleeder to the reservoir and cracked each line leaving the ABS. Then moved on to the calipers. If there is no air in ABS then regular vacuum might work. Personally, I recommend a pressure bleeder that has the right size reservoir cap (Euro size for saab and i think mercedes?). I think you can find inexpensive generic bleeders these days. Makes bleeding/flushing a wicked easy one man job.

 

[jvanabra]

x2. Highly recommend avoiding vacuum bleeders and sticking to pressure/positive systems. Vacuum based bleeders give inconsistent results, *especially* on ABS systems.

 

[mness4]

For better or worse I have a vacuum bleed system and will not be able to switch at this time. I've used this system successfully last time I bled this car (and another at the same time), so I have no doubt it would have been successful this time. The question is how to handle the master given the fact that it has run dry.

When I realized what happened, I asked my mechanic, who has been good enough to give me advice on issues that I'm trying to tackle myself. He's the one who told me it's no big deal. Just first do the standard two-person bleed on the master, starting with the connection closest to the driver and then doing the one farthest from the driver. Since he didn't know I was doing a vacuum bleed (as opposed to a two-person bleed) I thought I would ask here if a vacuum bleed would take care of the master as well. I'm also wondering what to expect from the ABS if I disconnect the lines at the master.


If a bench bleed of the master is required to make it perfect, that's where I would stop. In that case, hopefully I could get it driveable and take it in to be bled more thoroughly.


Thanks,
Mike

x2. Highly recommend avoiding vacuum bleeders and sticking to pressure/positive systems. Vacuum based bleeders give inconsistent results, *especially* on ABS systems.

 

[jmkcc]

I wouldn't shy away from bleeding the MC in the car. As long as you get the MC level you just remove the brake lines going into the ABS and connect a hose from the disconnected in into the brake fluid reservoir. Then just pump, air will pump out into the reservoir and the submerged hoses will not allow air back in so after a bit you will be circulating fluid and there will be no air in the MC to worry about.

I've read that the angle of the MC allows an air bubble to rise within the MC to a point where it will be above the inlet/outlet and impossible to remove unless you level the MC by jacking up the front or rear of the car. Not sure if that is true or not. If it's not true than you may get by just filling with fluid and doing a standard caliper bleed. But to be honest jacking up one end of the car and bleeding the MC into the reservoir is not much work so probably worth a try. I don't think it can make anything worse.