another problem

On this 996 3.4 c2 1998, I bought the car and have had to replace all the brake pipes, It had no brakes, and the pipes where rotten. so all the pipes replaced . Now I cant bleed the system. By pumping the master cylinder it makes a squeaky sound when pushing the pedal down, and nothing out of the calipers I am thinking it needs a new master cylinder also I cant get any fluid to the calipers even with a pressure bleeder. so i I think there is a problem in the master cylinder. any ideas Paul

Had the system lost all fluid due to burst brake pipe/s? Many variables here but can tell you if a brake pedal is pressed to the floor with no fluid in the system to limit travel of pusten in master cylinder it CAN damage the seals in the master cylinder. If the seals in the master cylinder are damaged obviously it will struggle to make pressure. However, and this is the thing, if the whole system, including all 4 calipers is empty it can be a hassle to get it bled properly. Usually though with all nipples loost and master cylinder reservoir full gravity will let the fluid creep through. Is the ignition on when trying to bleed them up abs/accumulator etc, perhaps a thought? As I said, many variables but IF your master cylinder was goosed you would usually still find fluid flowing through the system. Try clamping 3 flexis off and bleeding just one line and caliper, don't clamp the flexu too hard or it will damage the rubber. General rule is don't clamp a flexi as it might ght damage it but if your in the crap and desperate for results a gentle squeeze should be ok. I'm wary of giving advice on a forum as sometimes people take things literally. Anyway, just a few thoughts, hope you get it sussed.

I'm with Parsley. Fill the master cylinder reservoir, left the cap off, leave all bleed nipples open and see what happens overnight. You could also try leaving the pressure bleeder connected overnight - low pressure only, say 6-8 psi. As a last resort, you could connect the pressure bleeder and pump the pedal (gently, trying to stop and lift just before the bottom) to try to get the fluid moving. My worry would be if it's been open to the elements, what's contaminated/blocked the system. But hopefully it's just full of air. I watched an M539 YouTube video recently about resurrecting a BMW 323i and literally all four rubber hoses had degraded and blocked internally- but that had been open to the elements for 25 years! Good luck.

If the system has run out of fluid you are supposed to use PIWIS or similar to activate the ABS pump to finish the bleeding process. That doesn't sound like the issue here though, this is more fundamental. I'd go with what is suggested above. MC

Perhaps loosen the brake pipe unions on the master cylinder first and see if there is fluid in the master cylinder and it's coming out when the pedal is pressed SLIGHTLY. You will have to enlist a helper (if you don't already have one). Start at the beginning, is the master cylinder filling with fluid? then move along the line, is it coming out of the master cylinder. Maybe go back to basics. This should be easily solved. In years and years of running my own garage I've only had to change a master cylinder once!!! It's nearly always something basic.

I accidentally let the whole front circuit drain and just re-bled as normal. Spoke to a specialist re the abs pump and they never activate it when bleeding. Looking at new master cylinders on ebay the TRW brand, which I believe is OEM, is fairly inexpensive. As others have said, gravity should get the fluid through.