250 sl brake woes

[NONACK]

I'm fixing up a 250sl that has been sitting for 15 years.  I got it running, and most of the wiring works, but it has brake issues.  I have replaced the clipers and rotors on all 4 corners, and bled the system 5 times (twice conventionally, twice with a vacuum bleeder, and once conventionally again), but I cannot get the system to build any significant pressure.  The fluid is clean and free of bubbles, I have not found any leaks, and have used up an ungodly amount of brake fluid.  Any suggestions/ secret sl tricks I don't know about?  I was thinking of picking up a junkyard MC to test with in case that is the problem. Thanks in advance, great data base you have here.

[Shvegel]

Only asking because I have seen this before but are the caliper bleeders on the top of the calipers? They are supposed to be so if not swap the calipers from side to side.

[NONACK]

Yes, they are.  I assumed when bolting them on that, with the bleeder at the bottom, it would hold air in the caliper.

[rwmastel]

What do you mean by "cannot get the system to build any significant pressure"?  Do you mean the pedal goes to the floor?

First, also replace the rubber brake lines going to the calipers.  These deteriorage internally and cause lots of problems.  Second, check the one-way check valve in the vacuum hose between intake manifold and brake booster.  It may be installed backwards and preventing vacuum from reaching the booster.

[menesesjesse]

Since the car was sitting for such a long time there could be a lot of things.  The brake lines may be rusted and leaking by. You will never get a stiff pedal if this is the case.  Also I would pull the master cylinder and see if it has been leaking into the Power Booster.  My 1966 230SL sat for over 10 years and the booster had alot of brake fluid. The master cylinder internal seals apparently went bad over time and started to leak by each time the brake was pressed.  If it booster is dry, I would bleed the master cylinder by it self and then install it to bleed the rest of the system.  I hope this helps.

[NONACK]

Hey guys, thanks for the suggestions.  I bled the brakes again this morning, and it held pressure.  Drove the car, brakes mork beutifully.  I have no idea why the problem resolved itself, but I'm not complaining.