I've done some searching but can't find a definitive position on whether it helps to have the power on (to get power at the ABS unit) when bleeding the brakes. I was able to bleed the rears with no problems but not the fronts. I get nothing coming out of the front - no air...no fluid. When I try to suck fluid through the (open) bleeders with a vacuum pump, the system holds a vacuum and it drops slowly as air makes it way around the threads on the bleeders. The car had been sitting for years before I stumbled upon it and bought it. Could this be yet another case of needing a power bleeder to do it properly or should I be thinking MC or ABS unit?

 

I did mine with the power off, try to get somebody to help you pump the brakes and see if that works better than the vacuum.

 

I've always had poor luck using a vacuum pump to bleed brakes.

I would recruit someone to step on the pedal for you or replace the bleeders with speedbleeders. While the one-man-bleeder pumps are nice, nothing tops the pedal.

Dave

 

are you doing this by yourself? its pretty easy to bleed anything if you just have someone on the pedal while your doing it...if that doesnt work something might be wrong or stuck if it was sitting. you shouldnt need to have the power on. ive never bled the brakes on my 7 but i have done it on hundreds of other cars

 

I did it by myself and I had a buddy pump as well. Bleeding the rears was pretty predictable and worked well. The fluid squirted right out and the pedal dropped to the floor. The front, however is weird. No pedal drop and no fluid/air. The only way anything was coerced into coming out was by sucking with a vacuum pump. I plan to do the 929 MC anyway so hopefully putting a new MC on may eliminate this problem.

 

It could be anything in the system that's blocking it - work your way backwards towards the master, undo the brake line from the caliper and see if you can get fluid out of it. If not, remove the rubber line and see what you get, if not, go to the ABS pump, etc.

There's a blockage somewhere. Has the car ever had an engine fire or something? Could have melted parts in the ABS pump.

Dale

 

No, but I suspect it sat in the sun with the hood off for quite some time. The engine was out for some time and the previous owner never finished it. There was a lot of deteriorated rubber, including the clutch slave flex line. I replaced all the brake flex lines just in case and I think I'm slowly making my way up to the ABS unit.....but deep down I hope my troubles will end once I replace the MC.

 

+1 for the speedbleeders.

Also, when stepping on the pedal, only push it down halfway or so.

The accumulated junk at the end of the MC can chew up the seals pretty fast.

Another lesson learned the hard way, and then later explained to me by a mechanic.

 

What did you replace that is requiring you to bleed the system? Somtimes it takes a while to get the air all the way through. My best luck has been using a power bleeder and putting pressure at the master.

 

Nothing was missing as far as the brakes go, but I had no brake pressure when I bought the car (as is). I decided to replace all 4 flex lines when I realized that a lot of the rubber components had deteriorated. I will look for a power bleeder locally. That seems like my best bet and everyone who was kind enough to offer their opinion seems to agree on this issue. I'm even tempted to run a bit of pressure backwards through the bleeders to see if a chunk of crap floats up to the top of the master cylinder reservoir....lol.

 

Sometimes the only way to fix something is to to the right thing. On a 14 year old car the right thing just may be disassembly, clean/replace, reassemble. I worry about damaging connectors/threads/etc like everyone else, but for things that make you steer, stop, and stay level I err on the conservative side. If I can't go, I feel thats much safer than if I can't stop!

 

You're absolutely right. That's why I haven't even attempted to start the fresh engine. I'm concentrating on getting the brakes in order.

I actually took the master cylinder off and disassembled it. Lots of corrosion and junk inside. What worries me now is the fact that I pumped that crap all through the system.... I'll be getting a new master cylinder tomorrow so I'll follow up once I get things squared away.

 

That's pretty much guaranteed to destroy the MC.

Ever wonder why you should loosen the bleed screw before depressing the pistons to replace the pads?

There's a check valve in the MC that will get messed up if you run pressure through the lines backwards.

 

Wow....first time I heard of this....I've worked on all kinds of brakes over the past 25 years, from run-of-the-mill domestic to weird Peugeot and Renault systems and I've never heard of this procedure. Changing pads shouldn't require removing the bleed screw unless the fluid is old, in which case it is best to dump it rather than sending it back up. I've never had fluid not return to the reservoir by simply pushing the caliper piston back in.

I agree with you that running pressure back through the system is probably not a good thing....that's why I said it jokingly and added 'lol' at the end. As I mentioned earlier, I took the master cylinder apart and found all kinds of nasty crud inside....what scares me now is that that stuff probably found its way to the proportioning valve and ABS unit. I tried to find a power bleeder last night but no dice....

 

It's a closed system, so it has to go somewhere when you push the pistons in.

It's just easier on the system to loosen the bleed valve to have the fluid pushed out instead of pushed back into the system.

 

...indeed....back up where it belongs.... If bleeding or fluid replacement is required anyway, then what the heck...open up the bleeders but why complicate matters if you don't have to.... and when you push the piston(s) back in, how much pressure can you really exert on them anyway? It's mostly piston seal stiction that you're fighting against....virtually no fluid pressure other than slight resistance through the lines.

Let's see what my new 929 master cylinder will do for me tomorrow....

 

Hate to bump an old thread but having the same issues. Rears bleed fine. fronts...well, fluid comes out but barely. Is it just a bad valve? Really want my front brakes to work

 

Generally you do this to protect the ABS unit. The Vent/Compensating port will allow fluid to flow back to the reservoir, as when the brake fluid heats up it will expand. Modern MC's don't have any check valves in them. You must be thinking of MC's used with drum brakes. These had check valves to hold pressure against the cups in the wheel cylinders.

EDIT: Haha, just noticed this thread is 2 years old....

 

Holy cow....brought back up deep from the abyss

I ended up removing all the hard line connections and blowing crap out. I replaced all the flex hoses (OEM and unbelievably cheap) and put on a 929 master cylinder with a few modifications. Then I bled the system and way I went. I did have chunks of crud right at the ABS unit. Too bad my car gets driven once in a blue moon after all that work....I've sort of lost interest in giving up hours of my life with little return.