Soft to hard brake pedal

Hello everyone. I have a question I hope someone can steer me in the right direction. I have a 1985 325e that I am in the process of bringing back to life. One of the things I am stuck on is: when I bought the car the brake pedal will pump up, but then it slowly goes down to a hard pedal. I thought maybe it had a bad booster so I replaced it. Same thing happened. Next I checked the clutch master cylinder and it was leaking a small amount. Bought a new one and a new slave cylinder, put it all back together and it still won't hold the brake pedal up. I did also put all new disc pads front and rear and did bleed the brakes. I checked around the master cylinder and all 4 wheels and nothing is leaking. My reservoir has never gone down on the fluid level, telling me there is no fluid leak. Any ideas on where to turn now? Thanks in advance.

Originally Posted by 5kidsandawife

Hello everyone. I have a question I hope someone can steer me in the right direction. I have a 1985 325e that I am in the process of bringing back to life. One of the things I am stuck on is: when I bought the car the brake pedal will pump up, but then it slowly goes down to a hard pedal. I thought maybe it had a bad booster so I replaced it. Same thing happened. Next I checked the clutch master cylinder and it was leaking a small amount. Bought a new one and a new slave cylinder, put it all back together and it still won't hold the brake pedal up. I did also put all new disc pads front and rear and did bleed the brakes. I checked around the master cylinder and all 4 wheels and nothing is leaking. My reservoir has never gone down on the fluid level, telling me there is no fluid leak. Any ideas on where to turn now? Thanks in advance.

replace the lines

^ This!

Sounds more like an internal leak in the master cylinder to me. Rebuild or replace. May need sleeving for a rebuild depending on bore condition.

I will order a new master cylinder. I am curious though why replace the lines? What is the reason that would be an alternative? I just like more information for future problems.
I will report back when I install the master cylinder. I live in a very small town 2 hours from the nearest part store so I do everything online. Thank you for your input.

the brake lines from the hard lines to the caliper expand and start cracking which then could lead to a blown brake line. all 4 of them, plus is it one of those maintenance items then tend to be overlooked.

Thanks for the information.

Check your lines for ANY liquid. If your hard lines are all corroded, chances are some where along one of the lines, it's leaking. It could be a number of things but the lines are the first place I would check.