Wilwood spongy pedal(67 gto)

[keith4909]

I just finished my master cylinder install and after bleeding each corner three times and I'm am still plagued with a soft pedal. Im running a 7/8 wilwood mc and the 6 piston/12.88 one piece rotor kit. Did the wilwood tech recommend the wrong master cylinder?

My pedal ratio is 5.25/1
1967 gto
6 piston caliper
12.88 rotor
Rear drums
Prop valve installed
Car was originally a 4 wheel manual drum.

What should I do?


Thanks.

[andrewb70]

The fact that you have rear drums might be the problem. The rear drum cylinders need quite a bit of fluid to operate properly. The 7/8" bore master can generate good pressure, but it does not move a lot of fluid.

Have you driven the car? Does it stop well?

Andrew

[keith4909]

I haven't driven the car yet. The whole clip is off for the restoration. The problem is the pedal goes down to within 1-2 inches. Im going to call Wilwood in the morning to confirm. I told the tech line every spec. Im so pissed because I have the feeling i will have to r/r the master cylinder to install a larger mc. The whole process is easily a 3 hr job. Bleeding this wilwood mc was a total pita. The quality is also questionable. I had to pump out the fluid to remove a bunch of left over metal from machining. This whole kit was a pita to install. Im a mechanic and can install brakes in the dark. The first side took me forever to shim because you have to remove the hub every time you need to add/remove a shim. Lets see what happens. Thanks for your help. Maybe i can get some type of reimbursement for my time.

[Apogee]

What method did you use to bench bleed the MC? Plugged port or recirculation? Regardless of the method, once you thought you were done, did you plug both outlet ports and confirm that it hydraulically locked and was indeed fully bleed?

I'd be curious to know what Wilwood has to say about the metal shavings. We've sold a lot of those MC's and never seen that issue.

Tobin
KORE3

[Classic Nova & Performance]

I'd be very interested as well. Like Tobin we've sold quite a few and have never had the shavings issue.

[keith4909]

They didn't say a word. Just silence. I bleed the **** out of it. Im a mechanic by trade and know how important bleeding is. I bolted the mc to fire wall. Filled mc. Submerge tubes and had wife pump the brakes for like 10 mins while i hit mc with a closed fist to dislodge air bubbles . I think i may splurge for the rear disc set up. I have 4k in wheels and brakes. Whats another six hundred to complete the look.

[MrQuick]

Do what Tobin says. Remove your brake lines one at a time at the master and plug the master port then see what your pedal does. If you plug both and your pedal is better then plug off the fronts, if the pedal is bad then you have an issue with the rear.

Your a tech you have probably found the the pedal feel with improve after your pads are seated into your rotors.

[keith4909]

So i decided to warranty out the old master cylinder(amazon) because i found metal shavings in the reservoir. Installed the new one and pedal feels much better. I also put a pressure gauge on the caliper and i was able to get over 1400 psi. I guess i could have gone with a 1in master cylinder but the 7/8th master cylinder will suffice. I dont want to install it again. Thanks for all your help

[nasty72nova]

I've had a Similar issue. Same master cyl. Also had metal shavings. Problem is a I didn't see them until after I bench bled it. I lose pressure at the pedal an it is spongy at best. Summit is warrantying it.

[CTSV]

Add me to the list of metal shavings and issues, mine is being replaced this week. Is a total PITA to do the r/r on my car too. Bad quality control