So I replaced the master cylinder and I replaced the brake hoses with stainless steel ones and the pedal is certainly much firmer but it still sinks when I'm at a light. WTF is that?

 

Are you losing fluid?

If not, then you definitely have air in the system or your MC is leaking down under pressure.

Did you bench bleed your new MC?

 

make sure system is fully bled- only think left would be brake booster-

 

I did indeed prime the MC and as far as bleeding goes, I pushed almost the entirety of one of the large bottles of brake fluid through so I'm assuming it's properly bled. Could I have 1 or more bad caliper/s or wheel cylinders? Could the drums not be properly adjusted?

And if the booster was bad wouldn't it be difficult to push the pedal?

 

not necessarily ..i worked on a chevy tahoe that had a pedal that was losing pressure-
guess what fixed it- brake booster- if theres no fluid leaks on any wheel- then ur wheel
cylinders are not leaking or your front calipers--u said u primed the MC- what about your brakes itself?

correct me if im wrong- bump

 

There appears to be no fluid leaking. I primed the MC (recirculated the fluid back into the reservoir and pumped the pedal until there were no more bubbles and then some). I bled the brakes at each wheel (thoroughly.....I think). The pedal is firm, but it does need to be depressed lower than I would like to engage the brakes. But if I'm at a light I can keep pressing the pedal down, a little. As soon as I let off the pedal the pressure is there again. Maybe I'll get one of those self bleeding kits and go at it again.

Booster then huh? Any seconds on that?

 

x2 on the booster

 

I just performed all of the booster tests in the FSM and it passed all with flying colors.

 

Could someone please be so kind as to explain to me how this could be caused by the booster? My understanding is that it just makes it easier to push the pedal. Am I wrong? The FSM says that the pedal should sink some when it's held depressed. How much is that exactly in you experience? Maybe my brakes are fine and I'm just being picky.

 

Shoes that aren't adjusted all the way out causes the pedal to move further before resistance but not fade. Did you check under the dust boots on the wheel cylinders to make sure they're not leaking?

 

Hmmmmmm. No I didn't peek under the bots. Never thought of that. Will do in the morning. Thanks for the tip.

 

There is also the the piston seals on the calibers. If one of those is bad that can also give you the same affect.

 

How does one go about checking the seals on the caliper pistons?

And how does one determine if the drums are properly adjusted? Last time (the only time) I changed the stopper shoes I just put it in reverse and stabbed the pedal a couple times to facilitate self-adjusting. I have since heard that the self-adjusters don't really work. There is no hole to get in there to turn the adjuster like with most drum brakes.

 

your wheel cylinders or calipers could be leaking internally. your brake booster just makes it easier to push the pedal.

double check you have no air in the system. clamp off the brake lines at all 4 wheels.
have a buddy sit in the car and step on the brake (which should be rock solid). One wheel at a time, unclamp and see how far the pedal drops (reclamp after you unclamp each wheel. for this test) the wheel that drops the furthest is your problem.

you could also have a collapsed brake line too. are just a lot of air in the system.

 

How do you "clamp off" a brake line? Do you mean clamp the hose with a pair of vice grips or something like that? I can't do that since I now have stainless steel hoses.

 

what car is it

 

95 DX hatch.

 

bleed in this way
RR, LF, LR, FR

 

Yeah, I did. Just like it says in the book.

Could it be that the amount of pedal sinking I'm experiencing is normal? There should be some when the booster is working. How much? Maybe the car was simply never made to have a hard pedal that engages quickly.

 

new parts sometimes dont work.. I think its bad MC