Sinking brake pedal
 

'05 Element EX, 80K miles. NO external brake fluid leakage

If brake pedal is depressed with slightly more force than normally needed to stop car, pedal goes slowly to floor. Shop manual says 3/8" movement in 3 minutes is limit of acceptability with light pedal pressure. I had about 3" movement in aprox 4 seconds. Figured master cylinder was bypassing internally, So bought new Wagner master, bench bled, and installed it. Vacuum bled all wheels in correct order to remove old fluid, topping up master as required during bleeding. Now pedal does same thing, but seems to go down slightly quicker. First application of pedal results in pedal stopping half way down, but a couple further pedal strokes cause the pedal to "pump up" to the top, on application.

If there were air in system, I would expect spongy pedal, but pedal acts exactly like it would if there were a small system leak.

Manual instructions say nothing about bleeding ABS unit--Necessary? It IS a high point in the system.

Any way that ABS unit could be bypassing internally? But then, where would the fluid be going?

Car stops great, it's disconcerting when sitting at a light for the pedal to keep sinking, however.

I detest modern cars!

Gronk

Re: Sinking brake pedal
 

Your master cyclinder is going out.

Re: Sinking brake pedal
 

agreed, replace your master cylinder. bench bleed it first prior to installing

Re: Sinking brake pedal
 

I had the same issue with a clutch master cylinder on my CRV. Replaced a leaking OEM one with one from Autozone - bench bled it, installed it, bled thew hole system, worked ok but every once in a while it would sink. Not all the way to the floor, but I could put my foot under it, pull it up, and and would act like normal again for a while.

I'm done buying master cylinders that don't come from Honda.

Re: Sinking brake pedal
 

Like was others said, check out your master cylinder. Furthermore, check to see if there are any brake fluid leaking.

Re: Sinking brake pedal
 

Thanks for the responses guys, but if you re-read my initial post you will see that I replaced the original master cylinder with a NEW Wagner (I erred in the manufacturer the first post--now corrected). Bench bled, installed, system bled. Master was drop shipped from Wagner warehouse--it isn't a Big A, or Autozone POS. Both new and old acted the same. Thinking about the master cylinder which you all seem top think is the problem, the only way that I see that the pedal would act the way it does if the master were to blame is for fluid to leak past the cups and go into the power booster unit. NOT happening because there has been NO drop of fluid level in the master, and years ago I had a master leak that way, and when a slug of brake fluid made its way into the intake you knew it--engine raised hell--didn't like it one bit.

Since the first post I have bled the ABS unit(no air). Have also found that if the engine is not running = no vacuum, the pedal is high and hard. Start the engine and the pedal sinks--and NOT the little bit that you expect with power brakes--it keeps on sinking. Can't see that the diaphragm in the booster is leaking, because the engine would go lean when it was leaking down--plus the master piston would have to be moving right with it. Pulled the ABS fuse, only thing different was the idiot light on the cluster lit.

Gronk

Re: Sinking brake pedal
 

Check your brake lines as well for any signs of swelling and check the fittings.

Re: Sinking brake pedal
 

Problem seems to be with the spool valve in the booster

Gronk

Re: Sinking brake pedal
 

Gronk,

did you ever figure out the problem?

Re: Sinking brake pedal
 

Another thread says to try activating the ABS
Meaning is to try driving the vehicle and jam on the brakes to activate the abs system
It should clear out the slow fade or soft brakes.