Bleeding brakes, sucking air from Master cylinder?

[Jason in DLH]

Yes pedal to the floor. Bad?[emoji51]


Sent from my iPhone using Tapatalk

Yeah...I’ve read that you can blow a seal and/or damage the MC by doing this.

Here’s someone’s take on it..


Not only is it not-uncommon to blow lines while bleeding brakes, it's also fairly common to wreck a master cylinder when you full stroke it if it has nasty fluid in it. Rust can build up in the bore in the normally never used part of the stroke, then when bleeding the brakes you scrape the seal over the rust and now you get a sinking pedal.

 

[optimusprime]

So it could be a blown seal within the MC?


Sent from my iPhone using Tapatalk

 

[Jason in DLH]

Hopefully someone else can chime in here, because I’m all out of ideas!

Im really hoping a line didn’t bust!

 

[optimusprime]

Well on the plus side, there are zero leaks anywhere so probably not a line


Sent from my iPhone using Tapatalk

 

[George B]

So it could be a blown seal within the MC?


Sent from my iPhone using Tapatalk

I am afraid that what you hear is air being pulled in around the bore of the MC.

 

[optimusprime]

Oh do go on


Sent from my iPhone using Tapatalk

 

[George B]

I am afraid that what you hear is air being pulled in around the bore of the MC.

You could try using a mityvac to vacuum bleed the line. Once bled, if the pedal is soft the master is shot.

 

[optimusprime]

Im a total newb at this abs stuff. Is replacing the MC a nightmare job?


Sent from my iPhone using Tapatalk

 

[Jason in DLH]

So it could be a blown seal within the MC?


Sent from my iPhone using Tapatalk

I’m not exactly sure what happens when the seal breaks (never had it happen), so I don’t know what to look for there. Never had a line bust on me either.

Hopefully someone with experience to the aforementioned shows up to the party!

 

[Jason in DLH]

Im a total newb at this abs stuff. Is replacing the MC a nightmare job?


Sent from my iPhone using Tapatalk

Don’t quote me on this for I’ve never change a MC, but I don’t believe it is difficult. Just get rid of all the fluid. Change out the MC. Add fluid and re-bleed. But, this is where you would definitely need a scan tool that can perform an ABS bleed.