What a difference a clutch master can make!

So, over the last few weeks, I had really noticed a drop off in my clutch engagement/disengagement. Felt very gravely and notchy, and more often than not would go from 90% engaged to 100% on its own. Chirped the tires a few times in parking lots. Clearly something was not right.

I have a McCleod RXT with approx 10k street miles on it, and a new slave cylinder as of a month or two ago, as well as a McLeod braided clutch line. Last up was the master. All the symptoms I was feeling had my gut thinking it was all due to a failing master cylinder. My Shelby is currently my daily, so the last thing I needed was for it to fail on its own. Also, i plan to hit the track here in Phoenix now that the cool weather is here. I did NOT want to risk losing my clutch in the middle of a run. Thats a bad day right there.

I took it in to a local Ford dealer and after the Shop Foreman called me personally, they finally got what i was trying to describe. Replaced the master under extended warranty. I can tell you right now that the clutch feels 1000% better! Much of the chatter is gone, feels completely smooth engaging and disengaging. No more jerking engagement, and the advertised light clutch effort from McCleod is now present.

I had just under 40k mile son my car and considering how I use my car, I wasnt surprised to find the master was finally taking a dump.

Hopefully, if any of you are having a weird time with your clutch, remember that the master is the brains and heart of the clutch control. If you suspect something might be off, have it checked under the complaint of master cylinder failing.

TL;DR: Crappy clutch control performance. Suspected failing master. Ford put a new one in. Car now shits out Tiffany cuff links when using clutch. Me happy.

Which McCleod RXT clutch you have? The 6975-07M (the modular assembly) clutch assembly that just bolt right to the stock flywheel or some other RXT clutch?

That sounds like the p/n i used. It was bolt on and go using the factory 10-14 slave cylinder

Is it possible, that a stiffer clutch can wear out a master cylinder over time?

@ShelbyGT5HUN Not necessarily. The clutch master uses hydraulic principles to do its work. So, if the clutch master can generate say 15 psi of pressure for every square inch on its piston and the volume pushed through, the slave cylinder will be able to use that same PSI per square inch and volume spread over a larger area. Which is why the slave is so much bigger than the master on our cars.

I think what really took out the master was two things:

1. The actual materials used to make our masters. Ford uses a plastic housing and I believe a metal piston with a cup seal. Over time abusive use of the clutch could cause wear on the plastic "bore" of the housing. Hell, Id even say normal use will do it, though at a later date and higher mileage for failure. Also, see #2:

2. The bleed procedure on the hydraulic system is a joke. No bleeder at the slave means pumping the master several hundred times for a pedal. I had to change my clutch and slave at separate times. Also, had a leak from being an idiot and not replacing my o rings with fresh ones when I removed the braided line.

That was a TON of pumping to get air out of the entire clutch hydraulic system. I have to imagine pumping a dry master a few THOUSAND times over the last year wore it out some. Id sure love to know what the guys at the Ford shop do to bleed these things.

Ryan, at RJM Performance had a thread here earlier in the year about a high performance upgraded all metal clutch master he was developing using his own GT500 for the test mule. He's been VERY successful with the 370Z crowd. I emailed him and hes got some working production plans for our GT500s. Hes been super busy with 370Z orders this summer, but he tells me he can make a master if your interested. email him for more info. Great guy, very detailed. If I didnt have my car under ext warranty and just bought my slicks, skinnies and front skinny wheels I would have bought one of his units.

[email protected]

Thanks for the post! Honestly, I haven't liked my RXT since I put it in a year ago (RXT, braided line, slave, pilot bearing). Chirps a lot, very stiff, high engagement and I get a bad vibration when re-enaging in 1st gear (clutch-go clutch-go, in heavy traffic). I have over 80K on my car and its primarily a DD, but it does see the road course 2-3 times per year.
I had finally just learned to live with the annoying symptom during my commute, but I'm elated that there may be hope to get back some drivability....especially in stop and go traffic.
I'm not under warrantee anymore...do you know if the the master cylinder install complicated or time consuming? I normally do all my own work.

P.S. I'll be hitting AMP in the PHX West Valley in Dec if you want to do a great road course (best in the area, IMHO). Ill PM you details later this fall.

I think adding the dedicated clutch master cylinder reservoir is a key step to clutch feel. Mixing all that hot fluid from the brakes, and debris, isn't a good combo either!

@barspen: You definitely want to check out Ryans page. A stage 2 or 3 might be very well worth an investment. All those shifts on a road course will need a much more durable master. Ill be investing in one in the future for sure. shoot him an email and see what he thinks!

lexustech48 said:

@barspen: You definitely want to check out Ryans page. A stage 2 or 3 might be very well worth an investment. All those shifts on a road course will need a much more durable master. Ill be investing in one in the future for sure. shoot him an email and see what he thinks!

Click to expand...

THX...I sent him a note this morning.

The 13-14 clutch is a larger diameter master cylinder than the 07-12 and moves more fluid than the latter for a given clutch stroke. It will bolt up to your existing pedal assembly. I've done it and you may need to shim, the clutch stop with a washer because the piston rod will impact the cylinder. A small flat washer that allowed the push pin through the center was all I needed.

Catmonkey said:

The 13-14 clutch is a larger diameter master cylinder than the 07-12 and moves more fluid than the latter for a given clutch stroke. It will bolt up to your existing pedal assembly. I've done it and you may need to shim, the clutch stop with a washer because the piston rod will impact the cylinder. A small flat washer that allowed the push pin through the center was all I needed.

Click to expand...

Looking at the Part# 2140 (BRMC-87) for the 2011 and Part# 2140 (BRMC-190) for the 2013. Does the part # for the 2013 look familiar?

Also following up with RJM Performance to look at options.

barspen said:

Looking at the Part# 2140 (BRMC-87) for the 2011 and Part# 2140 (BRMC-190) for the 2013. Does the part # for the 2013 look familiar?

Also following up with RJM Performance to look at options.

Click to expand...

Looking at Tasca's site, it's showing the part no. for the 13-14, the same for 11-12. While the 13-14 may be the current replacement, the picture for what is shown for 07-10 is the same as the one that came out of my '12. The older version is plastic, the later is some sort of alloy. The 13-14 part no. is DR3Z-7A543-A. I corresponded with RJM a whole back. It sounds to me that he believes the GT500 clutch pedal assembly is too flimsy to do much good with the larger master cylinder. I take it he intends to develop a pedal assembly much like he's done with the Nissans. That's been a while back.

"Id sure love to know what the guys at the Ford shop do to bleed these "
While I don't have it in front of me I believe the manual instructs to use vacuum to remove air from clutch lines and slave. I have a master cylinder cap with a hose built in which I have used with a pressure bleeder ... I simply hook the hose to a vacuum pump (even the cheep one from Harbor Freight works great). Put the system under vacuum and all air is quickly pulled from system.

looks like i have a few more tools to buy. thanks man!

cstunkard said:

"Id sure love to know what the guys at the Ford shop do to bleed these "
While I don't have it in front of me I believe the manual instructs to use vacuum to remove air from clutch lines and slave. I have a master cylinder cap with a hose built in which I have used with a pressure bleeder ... I simply hook the hose to a vacuum pump (even the cheep one from Harbor Freight works great). Put the system under vacuum and all air is quickly pulled from system.

Click to expand...

You'll still need to pump the clutch pedal numerous times along with this process. Don't forget, your brake pistons will also retract under vacuum, so pump them several times until you get pedal back before attempting to move the car. First time I did this, I wasn't prepared for the brake pedal to go to the floor.

Good point regarding the brakes! That is an important step.

I'm planning to go with the OEM replacement Master and separate the clutch reservoir while I'm taking it apart. Job looks pretty simple, but a bit messy as I'm expecting brake fluid to leak. The RJM master was pretty pricy ($400), but I would like the ability to dial in the engagement point. May upgrade down the road.

@ Catmonkey - looking at the '11-'12 verses the '13-'14, the part/shape looks totally different, but not sure if those are just generic, stock parts picts. I use a Blowfish master cylinder brace and would like to make sure i can still use that if I opt for the '13-'14 master cylinder. Does it look the same from a dimension standpoint? Also, since I don't have the part in hand yet, did you put the washer on the end, between the brake booster? Guessing most of these questions it will be obvious, but want to ensure the reservoir fits, etc. and I will run trouble free if go with the DR3Z-7A543-A.

Appreciate the help and feedback!

Yeah, they look pretty similar. The 13-14 has a slightly bigger bore, but we're only talking 1/16" (13/16" vs. 3/4"). Other than that and one being plastic and the other alloy, they look virtually the same and bolt up the same way. You'll never tell it's different where it exits the firewall. I looked at the brace you mention and can't see that being an issue.

Here is the 13-14 MC.



Here's the earlier model.


Why they look so different is the orientation of the fluid hose, but what you don't realize is that the hose rotates freely 360*. The hose is in the correct position when installed in the car in the 13-14 photo. It would need to rotate 90* to the front (white plug) in the other photo. The plug is just to keep anything from getting into the master cylinder. It's absent in the other photo. I'll be happy to snap a better pic of my old one if that would help. It simply bolted right up to my pedal assembly and the foam bushing that butts up against the firewall worked the same for both master cylinders. Now, I'm not going to lie to you. Getting the pedal assembly out of the car ain't an easy endeavor. I removed the driver's seat to do that.

The clutch stop is on the pedal assembly in the cab. Take a look under your dash and you'll see a 1" plastic button that goes through a rubber washer toward the bottom of the assembly that the clutch can impact when it's depressed.

barspen said:

I'm planning to go with the OEM replacement Master and separate the clutch reservoir while I'm taking it apart.

Click to expand...

I did that too. I replaced the brake master cylinder with an automatic reservoir to get rid of the outlet for the clutch line. I drained the reservoir as best I could with a Mitey Vac and formed some heavy duty foil into a bowl underneath it when I separated them. No need to remove the master cylinder, the reservoir is a separate component. I'm using the Shelby remote clutch reservoir. It's way overpriced for what it is, but it's well designed and clean looking.

If you detach the clutch line at the transmission and the master and pump the pedal a couple of times, it will get rid of most of the brake fluid in the master cylinder. If you have the option to let it drain for a few days, it shouldn't be a real messy procedure. I had a flexible clutch line that I plugged into the clutch master cylinder and put a rubber nipple over the opposing end when I removed the pedal assembly.

Im a liittle jelly of the 13-14 M/C. ITs an aluminum housing, not plastic. Not sure why it didnt supersede for all shelbys