punkrockd

i'm only asking to make sure there isnt anything i've over looked or forgotten. but here goes.

my mom has a 90 accord and the brake pedal slowly sinks while applying pressure. i bled the brakes to make sure air wasnt the culprit.

my assumtion is the master cylinder is leaking. no leaking from the calipers or rear wheel cylinders.

i just need someone to tell me i'm right or wrong before buying her a new master cyl.


thanks guys.

mpumas

Master cylinder is the likely culprit. What happens is the master cylinder leaks because the fluid leaks around the one of the rubber seals in the cylinder. This can be caused by age (rubber cracking) or moisture in the brake fluid which pits the metal cylinder. Best bet is to buy a new master cylinder although I have had good luck rebuilding them but it takes special tools.

punkrockd

thanks for the reply. that is what i thought. i just wanted to make sure i didnt over look anything.

a new one is about 60 bucks. and it is for my mom. i prefer new over rebuilt.


thanks again


dario

jeffcoslacker

You have to change the resevoir over to the new one usually, maybe not on a new one, they sometimes have a resevoir on them.

Don't put the MC in a vice when working with it, it can ruin it.

Don't bottom out the piston when bench bleeding it, that's the most common cause for replacement MC failure. Bottoming is hard on the piston seals.

I find the easiest and most time effective way to bench bleed one is to go ahead and mount it up on the car with the bleeder hoses attached, fill it up, stroke the pedal slowly about 3/4 of it's travel, you can feel the air bubbles squeezing out through pedal feedback...when you don't feel any more, and the pedal starts to firm up a bit, it's bled. Take the bleeder off, hook up your lines and test, done.

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