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Old 03-29-2009, 08:14 PM   #1
K.Linchpin
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Default Clutch Slave/Master Cylinder failure?

Has anyone ever had their slave or master cylinder fail in their WRX? I recently installed a new transmission and clutch and after about 2 weeks of perfect operation, the clutch started to act up. The Clutch is a SB3 HDMM (Heavy duty street) and is noticeably heavier than the stock clutch, which I believe is what brought the problem out. What happens is, after driving for a few minuets and after many clutch engagements/disengagements, the pedal starts to feel crunchy or spongy and it requires me to press the clutch pedal in further in order to change gears. It also requires a little more force (possibly because I have to push it in further). The slave cylinder also makes a squeaking sound when it's acting up.

Here's what I did so far to troubleshoot. I re-bled the system. And after finding that that was not the cause, I took my car to a Flat and level parking lot when the clutch started to act up and sat there with the clutch pressed in all the way and the trans in 1st. To my surprise, after about a minuet of sitting there and not letting the clutch out any, my car started to crawl forward.

I have no leaks... my reservoir is at the max level and that never seems to change. So I kinda feel as though the problem is internal. Aside from the slave cylinder and the master cylinder, I don't know what makes up the clutch hydraulic system. Is there a check valve in the system that could be failing, letting fluid back into the reservoir and reducing pressure on the clutch? The slave cylinder does squeak when the clutch is acting up, but there are no leaks.. so I don't know if that's the problem...?

I need to get this resolved as it kills the driving experience, and it could eventually completely fail... but I don't want to just start aimlessly replacing stuff cause that'll cost $$$...

Thanks in advance!
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Old 03-29-2009, 08:24 PM   #2
Tgui
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I have similar issues but no answers. Here is hoping someone with know how chimes in.
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Old 03-29-2009, 09:24 PM   #3
MasterKwan
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If you sit there and the clutch slowly engages while you hold the pedal down, your master or slave cylinder is leaking down, I'd be inclined to think it's the master becase, I think the slave would leak out if it was leaking down, on the master, the fluid probably just goes back into the tank.

They're no different than brakes, if you don't service it, they get contaminated and wear out. Maybe the heavier pedal pressure pushed it over the edge.
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Old 03-29-2009, 09:56 PM   #4
Mulder
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You don't say how many miles are on your car, but from what you're describing I'd say the hydraulics are just about shot. The best way to deal with it is to replace BOTH the master and slave, and also either replace the line between them or blow it out to get rid of any crap inside that could contaminate the new cylinders.
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Old 03-29-2009, 11:21 PM   #5
K.Linchpin
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Quote:
You don't say how many miles are on your car, but from what you're describing I'd say the hydraulics are just about shot. The best way to deal with it is to replace BOTH the master and slave, and also either replace the line between them or blow it out to get rid of any crap inside that could contaminate the new cylinders.
127K. Stock trans and clutch until 125.5k. Trans still good when replaced minus the fact the syncros were a little tired. 02' mind you.

While I don't want to waste my personal time jerking around w/the same issue week after week, I would like to save some cash and just fix what is causing the problem UNLESS it is likely that both components are at their lifespan. And to be honest, for the 3.5 years that I've had the car, I've never serviced the clutch's hydraulic system. ... if that helps you with your diagnosis.

Quote:
If you sit there and the clutch slowly engages while you hold the pedal down, your master or slave cylinder is leaking down, I'd be inclined to think it's the master becase, I think the slave would leak out if it was leaking down, on the master, the fluid probably just goes back into the tank.
Well, unless there's more to the slave cylinder, I wouldn't think the slave cylinder is not the verdict since it's not leaking out of the cylinder it's self... Fluid enters the slave cylinder and moves the piston forward, and that's it, correct?

Thanks for your help thus far!
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Old 03-30-2009, 01:24 AM   #6
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Quote:
Well, unless there's more to the slave cylinder, I wouldn't think the slave cylinder is not the verdict since it's not leaking out of the cylinder it's self.
Isn't that what I said?

Quote:
I think the slave would leak out if it was leaking down, on the master, the fluid probably just goes back into the tank.
Which means if you don't see a leak, it's probably the master. The thing is, if the master's shot, the slave is probably not far behind. I think Mulder probably has the correct idea.
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Old 03-31-2009, 12:04 PM   #7
K.Linchpin
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You guys more or less convinced me to go the expensive route. If it is indeed on the way out, then I'll be annoyed when It breaks and I have to replace it and rebleed. Plus I still don't know which one is the verdict.

It'll cost me about $150 + s&h...

Is replacing the Master Cylinder as straight forward as it looks? Does anyone happen to have a guide on replacing it?

Quote:
and also either replace the line between them or blow it out to get rid of any crap inside that could contaminate the new cylinders.
suggestions on blowing it out?

Thanks again.
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Old 03-31-2009, 04:00 PM   #8
Mulder
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You're doing the right thing. It's false economy to only replace one cylinder, even if it's the one that is bad at the time. The increased pressure in the system from the one new cylinder will typically cause the other one to fail in short order.
To clean out the line, the best way would be to remove it and blow high-pressure shop air through it. If that's not an option for you, at least try running some clean brake fluid through it. That should flush out most of what's inside.
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Old 06-26-2014, 07:03 PM   #9
Heatstreak96
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Hi, Sorry for rebooting this thread but I'm having a similar problem. I didnt try the parking lot thing but so far this would be my 3rd master cylinder going out.

During normal driving I'll have pressure the first few times i use the clutch and as i step on it I get less and less distance on it. If i stay off the clutch for a bit longer pressure comes back.

Should I also just replace both? The slave doesn't show any signs of leaking...

So far I've adjusted the shaft on the MC and rebled the system which helped but I'm still loosing a bit of pressure.

Thanks in advance.
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Old 06-27-2014, 01:26 PM   #10
K.Linchpin
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Be careful when adjusting your MC. Try to follow the service manual on that. For the record, I never had to adjust mine. Once I replaced my slave and MC, the system had no problems holding the heavy clutch... Only my foot ad a problem with that then I had about 30-40k out of my south bend before wrecking w/out any issues at all.

Are you using the correct fluid? Could the fluid be eating your seals? Are you using a very heavy clutch and are your MC's new when u buy them or used?

I'd try the parking lot test. If your MC is still fairly new, it fails the parking lot test, then try a new slave.

Let us know what u find.
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Old 07-04-2014, 12:07 AM   #11
Heatstreak96
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Quote:
Originally Posted by K.Linchpin View Post
Be careful when adjusting your MC. Try to follow the service manual on that. For the record, I never had to adjust mine. Once I replaced my slave and MC, the system had no problems holding the heavy clutch... Only my foot ad a problem with that then I had about 30-40k out of my south bend before wrecking w/out any issues at all.

Are you using the correct fluid? Could the fluid be eating your seals? Are you using a very heavy clutch and are your MC's new when u buy them or used?

I'd try the parking lot test. If your MC is still fairly new, it fails the parking lot test, then try a new slave.

Let us know what u find.
Thanks for the advice.

I tried the parking lot test and it all seems normal. When the car is cold, it just seems like the fluid is taking a while to move back into the cylinder.
I'm was using regular DOT3 fluid, I just added in the DOT3&4 mix or w/e when I bled the clutch.

My MC was new when I got it and I got it about a year ago...I've only gotten new.
Oh and the clutch is just an EXEDY stock replacement so it shouldn't cause any trouble...

I'll try changing the Slave Cylinder like you said, just waiting on the paycheck lol.

I was also thinking of doing the delay valve delete but I dont think there is one on my car cuz it's an 02
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Old 07-12-2014, 12:52 AM   #12
daseca07
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my 07 wrx doing the same thing replacing the clutch master cylinder and slave Monday simple fix. good luck heat streak
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Old 07-12-2014, 01:14 PM   #13
Heatstreak96
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Quote:
Originally Posted by daseca07 View Post
my 07 wrx doing the same thing replacing the clutch master cylinder and slave Monday simple fix. good luck heat streak

Just did the same thing, went for the steel mesh hose too.
For now its working again. I just hope it holds up this time. last master cylinder only lasted a year >.>

Thanks again guys

Last edited by Heatstreak96; 07-13-2014 at 12:38 AM.
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Old 07-13-2014, 02:31 PM   #14
02BeastMode
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Anybody have any suggestions on here to find the best deals on Clutch Master Cylinders and Slave Cylinders? I have a 2002 WRX, with STI 6 speed Trans, VF34 turbo, 21lbs boost. Not sure whether or not that should make a difference but I'd rather add details for best suggestions. Also, which brand seems to hold up best?

Reason I am in the market is twice now, I could not get my car into gear after starting it and trying to drive it. Trying to put the shifter into any gear acts like its hitting a wall instead of engaging. Clutch/Flywheel are fresh and newer, just replaced trans fluid (Subaru Extra S). I could be wrong but all signs seem to be pointing to either the slave or master going out, so I figured I'd replace both to be safe. Car has 149,000miles on it and I am not sure that they have been changed at all yet, I have owned the car since 89,000 miles and I have not changed either up to this point.

Oh and thank you, any advice or suggestions will be GREATLY appreciated!
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Old 07-13-2014, 03:18 PM   #15
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I ask because I see brands like Dorman that are super cheap, then brands like Beck/Arnley that are middle of the road, then Nabtesco which is expensive. I would like to end up with the best bang for my buck If the expensive one is way better, then I'll go with that one, I'd just hate to spend all that extra money if it is unwarranted. I like the best deals of course, but I would prefer to not put cheap junk in my car that won't last. Anybody with knowledge here that can help will be appreciated. Thanks
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