so i got my new EBC Greenstuffs and started installing them had a small issue with getting the backs off but got them in went to do the fronts and couldnt get the front caliper bolts off, it was already like 11ish and i had to be at work at 6am , so i put the tires back on and drove home... now when i brake the pedal is still the same fell untill i slow way down, when i come to a stop or slow down over time the brake pedal slowly sinks reducking brake pressure.... i checked for leaks and checked my fkuid level and i dont know what this could be

 

after much much thinking , tinkering , swearing , and angst ... i believe my master brake cylinder is starting to go bad... its not leaking anywhere buti get the sinking pedal, but as soon as i let off the pedal completely and depress it again i have full braking force and then it sinks slooooooowly to the floor .... lol anyone selling a MC in good condition without messed up threads

 

Did you disconnect the lines to the rear calipers when you removed them? If so, check closely for fluid leaks at the rears.

If you did not disconnect the lines, and if there are definetly no leaks at any of the wheels or the lines, it's likely that the piston/internal seal in the master cylinder has failed and fluid is "leaking" past the seal from the front of the MC to the rear when you hold pressure on the pedal. You would not necessarily see external evidence of this condition. In this case, rebuild or replace the master cylinder and you should be good to go. Rebuilt MCs are available from several sources including Mazda and MazdaTrix.com.

 

My master cylinder went bad 3 weeks ago. The signs are...

1. Pedal sinks to floor with no pressure but will then hold pressure apon re-engaging the brake pedal

2. The above happens when there is no leaks.

If there was an external leak, at least one set of wheels would stop the car unless you managed to have a leak in both sets at the same time which is highly unlikely.

 

I think I have a used NA S5 master cylinder that I will donate if you pick it up. I am not far from Chambersburg and Gettysburg. If interested, let me know and I will verify that I still have one. PM me if interested.

Larry
Mont Alto, PA

 

J,

Here are some pics of the master cylinder I have. Compare them with the unit on your car. In the meantime, I'll see if the part numbers for the S4 and S5 MC are the same. This unit is from an S5, BTW.

 

According to a parts fiche comparison, an '88 NA master cylinder for a non-AAS car has the same part number as the '90 NA, so it should work. PM me to arrange for pickup or, if you are some distance from Chambersburg, I will ship at your expense.

 

pm me immed.