Figured this would be the place to ask, since many of you frequently maintain your brakes. For those of you that bleed your brakes with a friend, do you have your assistant pump the pedal all the way to floor then close the bleeder valve on the caliper?

Reason I ask is because I had to replace my master cylinder in the process of bleeding my brakes. I've been told that it can be bad on the MC's seals if you engage the pedal all the way to the floor. On a side note, when I bench bled my new MC, the directions mentioned to only push the piston in 3/4 of the way in, rather than fully engaging it.

 

I've never heard about the seals going bad from the assistant technique but it could be a possibility. thats what my friends and I do , guaranteed to eliminate all of the air bubbles inside the brake lines when it's to the floor...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Reza^ &raquo;</TD></TR><TR><TD CLASS="quote">I've never heard about the seals going bad from the assistant technique but it could be a possibility. thats what my friends and I do , guaranteed to eliminate all of the air bubbles inside the brake lines when it's to the floor...


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I also like the idea of the having a friend assist with brake bleeding rather than self bleeding... It's reassuring to visually see the air being removed from the lines (assuming you're using a transparent hose).

-However, I'm debating whether or not the assistant should push the pedal all the way to the floor. In my scenario, I replaced the original MC (200,000 miles) so it was probably due for replacement sooner or later, but in the case of daily driving the pedal never reached the floor until being bled...possibly straining the seals upon their intended limit

The other reason I'm concerned is because I originally replaced the front caliper and as a result had to replace the master cylinder. After the install of the new MC and bleeding the brakes the pedal felt perfect. Right afterwards I changed out the rear rotors and pads only to find that one of the rear calipers needed replaced as well (the caliper piston would not retract after rotating it clockwise). After I replaced the rear caliper and AGAIN re-bled all 4 corners of all the air, my pedal now feels "mushy", leading me to believe I possibly destroyed my new (rebuilt) MC. Btw, the rebuilt MC was from Autozone...so I'm not too confident of their parts' quality.

Any other insight is appreciated...at this point I think the skin on my hands has lost a layer to brake fluid


Modified by Nisif at 4:20 AM 8/20/2007

 

i think the seals are built tough and designed for constant use and pressure ...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Reza^ &raquo;</TD></TR><TR><TD CLASS="quote">i think the seals are "built tough" and designed for constant use and pressure ...</TD></TR></TABLE>

Are you pitching a slogan for Ford trucks?

I'll see what comes of it, I just want the damn air out of my lines at this point.

 

i dont push the pedal to the floor when i bleed honda brakes. learned that back in '03

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nisif &raquo;</TD></TR><TR><TD CLASS="quote">
Btw, the rebuilt MC was from Autozone...so I'm not too confident of their parts' quality.

Any other insight is appreciated...at this point I think the skin on my hands has lost a layer to brake fluid


Modified by Nisif at 4:20 AM 8/20/2007</TD></TR></TABLE>

the quality of them are so so. i work there and its not uncommon for customer to rbing them back to get replaced only after half a year of use. it could be due to user neglect or whatevet though, i dont know. but luckily it should be under a lifetime warranty, you can get that thing replaced as many times as you want as long as you remember the phone number you gave them when you first purchased it. as far as me, i replaced my m/c with genuine honda, because brakes is something i cant justify trying to save a few bucks on

 

This is what I have heard about MC's going bad after bleeding:

Brakes that have not been bled for a long time (your typical street car, with 50K miles), can build up corrosion and hard deposits in the back end of the cylinder. The piston in the MC does not normally travel this far back under normal driving conditions, but when you bleed the brakes and push the peddle to the floor it does. The corrosion and hard deposits can tear the seals in the MC during bleeding.

I have never had this happen to me on my race car but I have fresh fluid and bleed my brakes all the time, thus little to no crappy build up to tear MC seals, even if I push the brake to the floor.

 

and if your mc was leaking you would see a trail of fluid underneath the brake booster on the firewall or fluid on the pedal itself , right?

 

i've always been told not to push all the way to the floor,for the above mentioned reason of damaging the seals.i always just put a piece of 2x4 or whatever wood under the pedal.that way your helper can just push till the pedal bottoms on the wood-no chance for mistakes.i've never had a MC problem yet.
about a year ago i got a Motive pressure bleeder,and it's the best thing ever IMO.complete flush in minutes,and no helper needed.
Chris


Modified by TeamNextGenChris at 7:26 PM 8/20/2007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">and if your mc was leaking you would see a trail of fluid underneath the brake booster on the firewall or fluid on the pedal itself , right?</TD></TR></TABLE>

I bad seal on the MC piston will not leak fluid out of the unit. It will simply not apply pressure to the hydraulic lines.

 

just don't bottom it with excessive pressure. it should be ok.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by parislohan &raquo;</TD></TR><TR><TD CLASS="quote">just don't bottom it with excessive pressure. it should be ok.</TD></TR></TABLE>
i can't imagine the pressure from manual bleeding being higher than the pressure applied in a panic stop!
the helper needs to only apply enough pressure to depress the pedal,and can continue to push it to the stop(wood block,etc)once the bleeder is opened,if it isn't already on the stop.
Chris