Problem with GT3 Master Cylinder Install

Porsche Technical related discussions.

Problem with GT3 Master Cylinder Install

Postby J_DeLira on Sun Mar 17, 2013 4:40 pm

Installed the TRW GT3 master cylinder on my 2011 Cayman S today, and I've somehow made the excessive brake pedal travel (or "mushy" brake feel) worse. I suspect this is a result of a less than optimal bench bleed of the new master cylinder but can't be sure. The new MC didn't come with a bench bleed kit, so I improvised by holding the MC in a vise with the reservoir attached to the top of the MC while a friend kept the holes that connect to the brake lines plugged while I slowly pushed the piston in and out.

Another potential issue during the install was my inability to attach the new MC into the brake booster with the reservoir still attached because the reservoir was in the way. As a result, I removed the reservoir, attached the new MC and then reinstalled the reservoir. After getting everything reassembled. I filled the reservoir, and bled the system twice (via the calipers) using a Motive Power Bleeder.

So far, I've seen no improvement in brake firmness... In fact, it feels softer now. The only other thing I can think of that's causing this (besides possibility of an incomplete bench bleed) is that I have the wrong part. I ordered the part from ECS tuning and the part number on the box does match the part number listed in other threads on this site. I'm sure that possibility is a long shot but really can't think of any other reason why this is happening.

Did I miss a step? I'm thinking my only two options at this point are to remove the MC, bench bleed (with a kit this time), and bleed the system again. Or, hand it over to one of the pros at my local independent shop and have them do the same thing but also flush the ABS (which I am unable to do).

Any thoughts or suggestions are greatly appreciated.
Jerry Delira
J_DeLira
Member
 
Posts: 7
Joined: Fri Jan 18, 2013 12:24 pm

Re: Problem with GT3 Master Cylinder Install

Postby ChuckS on Mon Mar 18, 2013 10:50 am

I am no expert, and defer to the "Pros", but I had an issue with soft pedals after a fluid flush.
Problem turned out to be an air bubble in the ABS unit. Solution was to go for a drive and find a safe spot to "STAND" on the brakes a few time and engage the ABS. Bubble went away and firmness improved dramatically. Then did a final caliper bleed and problem completely solved.
Chuck Sharp
1988 911 Carrera 3.2 Targa C.E.
1988 944 Turbo S
1986 944 Spec
and Several X Cars
User avatar
ChuckS
Time Trialer
 
Posts: 469
Joined: Tue Apr 03, 2007 4:03 pm
Location: Rancho Bernardo

Re: Problem with GT3 Master Cylinder Install

Postby J_DeLira on Tue Mar 19, 2013 10:31 am

ChuckS wrote:I am no expert, and defer to the "Pros", but I had an issue with soft pedals after a fluid flush.
Problem turned out to be an air bubble in the ABS unit. Solution was to go for a drive and find a safe spot to "STAND" on the brakes a few time and engage the ABS. Bubble went away and firmness improved dramatically. Then did a final caliper bleed and problem completely solved.


Thanks, Chuck. Going to attempt another bleed today but using slightly different technique. Will use both brake pedal and power bleeder. Also, won't open bleed nipples on calipers as much this time as I was warned I could be letting air in. If that fails, I'll like try activating the ABS in a safe place. Thanks again for the suggestion.
Jerry Delira
J_DeLira
Member
 
Posts: 7
Joined: Fri Jan 18, 2013 12:24 pm


Return to Technical

Who is online

Users browsing this forum: Google [Bot] and 40 guests