Master Cylinder Test

I put a pair of the wilwood and wagenswest adapters on the front of my 944 and cannot get the brakes to bleed. I had a horrible time doing it the first time and this time I can get a firm pedal but as soon as I crank the car the pedal goes to the floor. I am running the hydro boost setup with turbo brakes on the rear. I have bled the brakes with the car off with the car on, reverse bled them, used a power bleeder, tried everything with the same result. Must have bled them a dozen times. Before I buy a new mc I took the old one off and put it in the vise. Bled it and then I blocked off one of the hoses and the plunger goes all the way in with out resistance. I blocked off the other hose and it went in about halfway. I blocked off both and it was solid as a rock. Is the one seal bad and just bypassing?
Thanks for any help,
Lee

BTW this is an ABS brake system

Since no one has responded I asked a couple mechanics at work and they say the MC is bad. There are not any of the MC”s that are compatible with ABS available at a reasonable price. Are there any other options for a MC? I am not going to pay $750 for a MC.

What year and model 944 master cylinder?

1989 944 Base with ABS

Part number 951.355.011.01

So, it looks like ATE makes a new MC for under $250.

I have called every Porsche part dealer in the US I can find and no one has one even though a lot of them show them in stock. Apparently ATE stopped making them. If you know something different, please let me know.

I bought a used master cylinder off eBay and have the same result. I bled the brakes back forth and got a really hard pedal. As soon as I crank the engine, the pedal goes to the floor. Any ideas? Losing my mind bleeding brakes.

That sounds like a bad Hydroboost, incorrect plumbing, or a pushrod that is too long.

knucklehead12 wrote:I bought a used master cylinder off eBay and have the same result. I bled the brakes back forth and got a really hard pedal. As soon as I crank the engine, the pedal goes to the floor. Any ideas?  Losing my mind bleeding brakes.

Is there any way to test a hydro boost? I bough5 it new from Kent 2 years ago. Hardly any miles on the car.

I spent most of the day bleeding brakes to no avail. I am running the Ford hydroboost with turbo rear brakes, stick master cylinder, and wilwood dynalites up front. I get a firm pedal with the engine off but as soon as it is started the pedal goes to the floor. I go back and bleed the brakes again and there is air in the lines. There are no leaks anywhere. I have bled the brakes with someone pressing on the pedal, reverse bled them and same result. Any ideas are appreciated.

When you bleed the brakes where is most of the air coming from? Maybe your new wilwoods have a bad seal even though they're not leaking? If you still have your old calipers maybe put them on and see if you can get them bled.