Need diagnostic help, please!

[hiropro42]

So I own a '99 Legacy Outback, 226,000+ miles, give or take. Second transmission and clutch, about 130,000 miles ago. New clutch slave cylinder less than 10,000 miles ago.

 

I was on my way home from work the other day, when, after stopping at an intersection, I lost almost all pressure in the clutch. It felt like someone had opened the bleeder screw on the clutch slave and let all my juice spray out. First and second became very stiff to shift into, and before long I had to resort to near-perfect rev matching to get the trans to shift at all. I limped home (thankfully only about 8 blocks, with two stop signs) and popped the hood, expecting everything near the airbox to be covered in brake fluid. No such bad luck. I put a 4' square of cardboard under the firewall and pumped the clutch pedal a dozen times or more, checking for leaks. Nothing. Master cylinder's reservoir was slightly below the full line, so there was nothing leaking out. Today a friend and I were poking around, and we noticed that, with the clutch pedal depressed, the clutch fork has an awful lot of play. Like he said, I'm not all that familiar with Subaru's clutch setup, so I don't know if that kind of wobble is normal or if it's indicative of whatever's wrong. The gears don't slip at all, once they're engaged. The other odd thing is that the clutch fluid is pretty dirty, considering that it all got replaced a few months ago when I replaced the slave cylinder. I figured that'd be the case, but only if this really is a case of the internals of the master cylinder just falling apart. Previous owner was my brother (and the original owner); he said he didn't think he'd ever had the master replaced, so it's likely OEM. I've already got a new master ordered, but I'm really hoping I won't be after a new clutch as well.

 

Ideas?

[logic23]

clutch fork might have broken. Seen it/repaired a couple times

[hiropro42]

Can that be fixed without dropping the transmission?

[nipper]

Usually when the slave goes, the master should be replaced. With the free play was the slave cylinder extended?

[idosubaru]

hydraulic clutches (subaru's are my only experience), are not the most reliable systems. i wouldn't be surprised for it to be the master.

 

also - the hose is always recommended replaced with the slave, i'm not sure why but that seems like a common thread to Subaru and others i've heard from. not sure if they fail other than leak but i've always replaced them with the slave cylinders.

 

doesn't sound like the system hasn't been open recently meaning it has trapped air?

 

so there's 100,000 miles on the clutch - do you know if the springs were replaced (i think the hydraulic clutches still have those, i'm forgetting)?

Edited August 14, 2010 by grossgary

[hiropro42]

I'm guessing the springs got replaced for two reasons: 1.) the mechanic he was using was a pretty trustworthy guy who used to suggest stuff like that and then provide the parts at cost--he wasn't one to let that slide in order to guarantee another visit down the road; and b.) if they hadn't been replaced, would they have trucked on for another 130,000 miles? Plus, I think they're included in a clutch kit... Either way, no, I don't know for sure...

 

The hose, though, that's interesting: the parts guy at the nearest Soobie dealer said his system recommended the hose be replaced with the master, not the slave, and none of the three guys I talked to before doing the slave said anything about the hose. Incidentally, it looked fine when I did the slave--no cracking or peeling or brittleness. Regardless, there's another on the way with the replacement master.

 

My reason for zeroing in on the master (or possibly the clutch fork, now that that's been suggested) is that the clutch doesn't slip, it's just not engaging and disengaging properly. I'm hoping that when I get the master off the firewall, I'll see a pretty worn piston with plenty of clearance around it. That'd explain both the problem and the dirty fluid.

 

I would have removed it today to check it out, but it's been raining here all day, and as the car's immobile at the moment, moving to drier work space wasn't an option.

[hiropro42]

doesn't sound like the system hasn't been open recently meaning it has trapped air?

 

The last time it was opened was the beginning of April, when I replaced the slave. It's been running fine up until now, so I'd discounted air in the line, but since I've got a big bottle of brake fluid laying around, that'll be the first thing I do in the morning. Though now that I think about it, there is a *little* tiny bit of pedal that seems to come back when it's completely depressed, but that could just be my imagination.

 

If bleeding it doesn't make a difference, I'll take the master out and check it out. I just got ahold of my brother's Haynes manual for this car (thank you sweet zombie Jesus), to that should help speed things right along.

[nipper]

Nothng to "check" on a MC, it is just blown.

 

nipper

[hiropro42]

Nothng to "check" on a MC, it is just blown.

 

As true as that is, how can I tell until I take it off the car and check?

[Scoobywagon]

As nipper said, there's really nothing to check. The fact that you were able to move the clutch fork by hand AT ALL while the clutch pedal was pressed means precisely one of two things. Both have been mentioned. Either the clutch fork is not under tension because it is broken, or it is not under tension because the slave cylinder is not applying force to it. Of the two, a failed hydraulic component is more likely. Given that the slave cylinder is a recent-ish replacement, and the fact that you aren't leaking, you're pretty much down to a master-cylinder. It COULD still be a slave cylinder, but I doubt it.

[hiropro42]

Nice. Thanks for the help, all. I haven't had time to get under the hood yet today, and I likely won't, but at least my hair-pulling is calming down. Aggro (named for one of Steve Irwin's crocs, I think) is my daily driver, and she doesn't like sitting idle for long. Also, I was lamenting the idea of having to swap out the clutch altogether. I'll post the results (and maybe some pics) on Tuesday, when the new part gets in.

[nipper]

I usually replace them in pair, and i also recomend that. They both see the same amount of work, and bsically are built the same except one has a resivoir.

 

nipper

[hiropro42]

I usually replace them in pair, and i also recomend that. They both see the same amount of work, and bsically are built the same except one has a resivoir.

 

Good plan. I should've thought of that, and I guess I'm not surprised, now that I think about it.

[hiropro42]

So, got the master replaced this morning, and now I'm just waiting around for a buddy to get off work to help me bleed the system. The rubber fittings in the old one were almost totally disintegrated, so that's pretty obviously what the problem was. Didn't replace the hose (mostly due to time constraints and a lack of a desire for bloody knuckles today), but I've got a spare, should that come up anytime soon.

 

Thanks again for the help, guys.

[johnceggleston]

i ruined the slave cylinder in my 90 nissan pick-up by using the wrong fluid. it was already in need of repair but the wrong fluid made it leak like the line was cut. i don't remember what i used, brake fluid maybe, but it ate up the slave cylinder rubber parts.

 

make sure you are using the correct fluid and if in doubt, flush the system. you do not want to do this twice. of course since you have swapped both cylinders there's not much fluid left in the system.

[hiropro42]

make sure you are using the correct fluid and if in doubt, flush the system. you do not want to do this twice. of course since you have swapped both cylinders there's not much fluid left in the system.

 

Actually, there are stickers plastered all over the engine compartment about using 3 or 4 brake fluid as hydraulic fluid in this clutch, so I made sure to grab exactly what they said. If their own choice of hydraulic fluid is eating away at their seals, I'd've thought someone would have picked up on that by now. At least, I'd hope so...

 

And hey, everyone, guess what? On top of all this master/slave drama (sounds like a bad episode of South Park right there), I now need a new clutch fork and a pivot. Got everything bled out and functioning properly, started her up, headed out for a trip around the block, and just as I let the clutch back in to climb into my driveway, there was a pretty sharp *CHUNK* and the problem started all over again. Now I have pedal only in the bottom half of its range of motion, and it won't return to normal position without a helping hand. Popped the hood, took out the airbox and grabbed my flashlight to see that: ta daaaa! There's now a solid 15-20 mm of lateral movement in the clutch fork where it meets the slave. Specs call for 3-4 mm, max. The pivot's ball head is no longer visible, since it appears to have punched straight through the stamped steel of the fork. Wahoo.

 

Given that the clutch itself has about 130,000 miles on it, it's also getting replaced, since the tranny has to come out to get at the fork and the pivot anyway. It's possible I may have sheared off the lip on the edge of the release bearing, but that won't matter. Time to call my uncle and trailer the car out to the shop with the hydraulic lift; this is waaaaay too much for my driveway to handle.

 

There goes my week.