Brake Issue - Master Cylinder?
Brake Issue - Master Cylinder?
Long story short, I had to have someone help bleed my brakes and I'm fairly certain he was putting the pedal to the floor when he was braking to get the fluid out. was reading something and chatted with a few people, and turns out this can wear the piston in the master cylinder by traveling by debris/contamination that it normally does not when you brake normally.
How it feels different: I pump the brakes 3x (car on for booster) to get that firm feel - I squeeze a little bit harder, and the brake sinks a good bit. I just want to make absolute sure this sounds like a master cylinder issue before I replace the master cylinder.
I have bled the brakes twice since, no air coming out, so it's not air. I have had stainless lines for quite a while.
Here's a more eloquent description of the issue I think I have:
Please advise! I will test it at autocross tomorrow to see how it feels there.
How it feels different: I pump the brakes 3x (car on for booster) to get that firm feel - I squeeze a little bit harder, and the brake sinks a good bit. I just want to make absolute sure this sounds like a master cylinder issue before I replace the master cylinder.
I have bled the brakes twice since, no air coming out, so it's not air. I have had stainless lines for quite a while.
Here's a more eloquent description of the issue I think I have:
I bleed manually, but would use a power bleeder if I had one. Something to think about, but isn't a problem on well maintained cars is this. Over the lifetime of the master cylinder, it works within a given range of travel, I'm talking about the movement of the piston and seal assembly in the bore. Over time and with a collection of moisture and contamination, the end of the bore is probably a bit rusty, at least not smooth, and has goo (technical term) in there too. Now it's time to flush the system and the pedal is repeatedly pushed down to the floor. Pushed through a possibly pitted or rusty master cylinder bore. In my opinion this could reduce the life of the seals, requiring replacement of the cylinder sooner rather than later.
Of course, it's not going to last long anyway if in the shape I described above. Plus on a car like these with much better brakes than a civic, the brake systems are treated better by their owners anyway. Just something to think about.
But, if using a power bleeder, the pedal would never hit the floor, the master cylinder seals would never meet any pitted cylinder walls or goo that might be in the bottom travel of the master cylinder.
Of course, it's not going to last long anyway if in the shape I described above. Plus on a car like these with much better brakes than a civic, the brake systems are treated better by their owners anyway. Just something to think about.
But, if using a power bleeder, the pedal would never hit the floor, the master cylinder seals would never meet any pitted cylinder walls or goo that might be in the bottom travel of the master cylinder.
I've also noticed I hear the brakes "groan" - not the pad/caliper squeal or anything. Sounds more like some kind of pressure issue, hard to describe.
Sounds like:
but less clicky, more moan-y
Sounds like:
but less clicky, more moan-y
As far as groan, that could be just simple firewall deflection. The firewall does deflect. I measured it w/a dial indicator a few years ago before installing the master cylinder brace
You just bled the brakes, no pad change?
It is true a manual bleed can effect the M/C seals because of the normal piston travel range vs full stroke of the cylinder.
FYI new friction will have more compressability due to the friction thickness than a worn pad.
Different frictions will vary of their compressability amount, if you are sensitive under high pedal loads you can feel the stroke difference.
Just throwing that out there.
It is true a manual bleed can effect the M/C seals because of the normal piston travel range vs full stroke of the cylinder.
FYI new friction will have more compressability due to the friction thickness than a worn pad.
Different frictions will vary of their compressability amount, if you are sensitive under high pedal loads you can feel the stroke difference.
Just throwing that out there.
You just bled the brakes, no pad change?
It is true a manual bleed can effect the M/C seals because of the normal piston travel range vs full stroke of the cylinder.
FYI new friction will have more compressability due to the friction thickness than a worn pad.
Different frictions will vary of their compressability amount, if you are sensitive under high pedal loads you can feel the stroke difference.
Just throwing that out there.
It is true a manual bleed can effect the M/C seals because of the normal piston travel range vs full stroke of the cylinder.
FYI new friction will have more compressability due to the friction thickness than a worn pad.
Different frictions will vary of their compressability amount, if you are sensitive under high pedal loads you can feel the stroke difference.
Just throwing that out there.
thanks. I autoxed it over the weekend to see and it felt okay - a relatively hard stopping point, just lower than before the pad & bleed
Did you end up replacing the master cylinder? I have the same issue now including the flex noise that I didnt have before. The pedal travel went in deeper and felt spongier during autox
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yeah but my issue want that i did get amc brace too which I just took off if you're interested but it's probably not that either
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