Clutch haudraulics reconditioning

[keeweechris]

Yo, I've got a 1997 WRX with an annoying clutch hydraulic system.

Most of the time it works fine, but occasionally (once a week) something suddenly goes weird, and the hydraulic system shifts the contact-point of the clutch. Ie, the pedal goes hard, the contact point is near the top of the pedal travel, and pushing the pedal to the floor probably over-extends the clutch spring. Then say an hour later it returns slowly to normal.

Its not a complicated system, and most moving parts are in the master cylinder, so I went in search of a new one. But it seems aftermarket manufacturers don't make them, and Subaru charge over $300 for a genuine one.

So I bought a used one from a wrecker, cleaned it up internally (looked ok) and fitted it/bled it. Now it is sloppy when first used in the morning, but after a few pumps it goes normal, but returns to sloppy overnight.

Fcuk. OK, so does anyone know if I can buy any reconditioning kits for the master and slave? From memory there is only 2 rubber bits to the internals of the master cyl.

And secondly, does anyone know the correct bleeding procedure? I've found loads on the net describing bleeding subaru's, but none which describe the exact setup on my wrx. There is some sort of extra lengths of hydraulic piping which goes up to around the drivers-side bonnet hinge, and incorporates another bleed port. I think this is some sort of air-bubble-trap (being the highest point in the system) but some clarification on that would be good.

Thanks guys

[Guest keltik]

Easy fix is to get rid of all the extra piping and just run a small length of microbore to the slave cylinder.

Im not aware of any seal kits

[keeweechris]

Cool, thanks keltik.

It never ceases to amaze me how useless and unhelpful and up themselves Winger staff are! I went in to buy an oil filter and then talked to the service guy behind the counter, thinking he must know (if anyone did) what all this unnecessary looking clutch hydraulic piping was for. He poked around for a while, then thought it was some sort of valve, but didn't really seem very confident. I asked if he had seen anything like it before, and he said no. He then asked if it was an import... yeah, course it was, like 90% of all 199X subaru's, to which he laughed and said that explained it... the imports are strange beasts, and didn't seem at all interested to help me. So don't Winger know much about imports? Right.

I went to Sterling Clutch and Brake (to buy oil) and asked that guy. He was really confident it was some sort of Hill Start mech, until I pointed out it wasn't linked to the brakes in any way. So he didn't know. Great.

Thinking my car must be 1 in a mill, I went to Pick a Part to find a new slave cyl and connecting piping. Just about all their Legacy's had exactly the same network of piping! Ay? So Winger who are meant to be the Subaru guru's hadn't even noticed this, or seem to care about finding out. Makes me question mechanics knowledge and enthusiasm everytime I speak to them, especially wingers.

Anyway, rant over. I'm gonna simplify the piping with one off an old Legacy RS, and replace the slave cyl from the RS too. If this doesn't fix the system, nothing will.

[Guest]

which winger did you go to??

-smurff

[kamineko]

i had similar issues when i replaced my clutch system. its a prick to bleed.. there is a process to it, but i found that with trial and error so i can't explain it sorry

the extra length of piping is likely a dampener to prevent engine vibration transferring to the pedal. apparently its common on diesels.

[Joker]

whole new slave is like $70

[keeweechris]

So kamineko, you know the piping I mean??!! You're the first person I've encountered who actually acknowledges its existence!! Haha.

Yeah, I'm thinking its a dampening system too. But also something to catch air bubble and trap them at the top. It goes out of its way to travel up higher than the mast cyl, and has a loop which comes right down beside the mast cyl, then back up. That to me screams air bubbles. Anyway, when I install my new mega-simple pipe section, bleeding should be easy.

Oh, and btw, slave cyclinders at PickaPart are $10!!

The Winger I went to was Greenlane. Never had a friendly experience up there. The guys at the counters seem more interested in acting all cool for the hot blondes they employ, than being interested in your cars.

[Guest keltik]

I had the same pipework on my old GT. Was way too hard to bleed so just stuffed a hydraulic line from a BH on the car. Much simpler.

I have no idea why it was added. All i know is it isnt really needed.

[Guest boostcut]

you need to change mechanic, now! every decent mechanic will tell you its a hydraulic damper. its because vibrations are easily transfered thru oil thats under pressure. +1 to buying a new slave, and get a mechanic to make a new pipe from master cylinder to the hose off the slave, or send me the ends off the pipe and il make you a braided hose up.

[keeweechris]

I don't actually have a mechanic... I do most stuff myself. Only reason I went to Winger was cos they sell genuine Subaru oil filters, and seeing they purhaps see more subbies than anyone else in my area, they would know what the pipes were for.

OK, so you reckon just having an extra long array of hydraulic line between mast cyl and slave would (by adding length to the system and therefore more volume of oil) create a dampening effect? BTW, adding length to an oil line won't reduce the pressure of the oil.

Yeah, I'll buy new parts if these 2nd hand parts don't change anything. Can't really argue with a $10 non-leaking slave and piping from Pick-a-part! Thanks for the offer to make a line up, but part of that $10 bought me a stock line which should do the trick.

[Guest boostcut]

 keeweechris said:

I don't actually have a mechanic... I do most stuff myself. Only reason I went to Winger was cos they sell genuine Subaru oil filters, and seeing they purhaps see more subbies than anyone else in my area, they would know what the pipes were for.

OK, so you reckon just having an extra long array of hydraulic line between mast cyl and slave would (by adding length to the system and therefore more volume of oil) create a dampening effect? BTW, adding length to an oil line won't reduce the pressure of the oil.

Yeah, I'll buy new parts if these 2nd hand parts don't change anything. Can't really argue with a $10 non-leaking slave and piping from Pick-a-part! Thanks for the offer to make a line up, but part of that $10 bought me a stock line which should do the trick.

i realise that, and am quite familiar with PASCALS LAW. i play with hydraulics for a job

[keeweechris]

Great, can you please explain how the dampener system works again. I'm a mech engineer, so should be able to understand any terminology.

[kamineko]

i thought the line itself was allowed to flex/expand/contract

[Guest boostcut]

the length of the line obviously increases the "volume" of oil. its like doing a dive into a paddling pool or a deep pool.

pascalls law does not relate to any fluid contained in a rubber or easily malleable tube as it will expand.

most new cars have the clutch damper system. manual 1 series bmw have a small accumulator to help dampen vibrations even further.

[Guest keltik]

I also dont quite follow how an extra few feet of pipe will dampen vibrations. Assuming the fluid isnt compressible and the line doesnt expand - wont the vibrations be transmitted just as efficiently whether the pipe is an inch long or a mile long? Im not saying your wrong, i just dont actually know how that works.

This link pretty much confirms it is a dampener.....but my question stands. http://garage.projectraine.com/content_guides/240_clutchdamper/clutchdamper.html

[Guest boostcut]

good question. but i cant really answer for the nips that were probably paid billions of yen to develop the system.

but in saying that, its only there for drive_ability

[keeweechris]

Thanks for that link! That Nissan setup is almost identical to the Subaru one.

OK, heres a random idea... assuming theres no magic going on in the 3-way joint, or the one at the end with the nipple, how about if the section between the 3-way and the nipple is purposefully partially filled with air (or nitrogen), maybe through the bleed nipple. That would create a dampening effect, and being the highest point of the system, the air should stay put. Yeah, I know the whole objective of bleeding was to remove air, but other than that, I can't see how adding length alone would reduce vibrations. Does air "dissolve" in hydraulic fluid?

Seeing as all the 199X legacy's at PickApart had these delightful gadgets, maybe the legacy service manual might hold the answer.

A proper dampening unit is installed in RHD subaru's of the same age. This was for US drivers, who (embarrassingly) weren't regarded as capable to crank a smooth gear change ;-) Its all in black and white in my service manual. The RHD model doesn't have the dampener. It is a small box located between flexible pipe from slave, and solid tube from master. Inside is apparently some springs and a piston, to properly absorb the shocks. Then later on, the 03 wrx's sold in US had another system mounted to the slave, which everyone removed... documented all over the net.

So, with all that in mind, I find it hard to believe the extra lengths of solid hydraulic pipe is a dampener system. Why put a bleed nipple on the end? Why split it with a 3-way joiner? Why take the 3rd leg right down beside the master cyl reservoir, then loop back up, following the min/max lines?

Still, I've been known to eat a hat or two in the past.

[keeweechris]

I'll find out for sure when I remove all this mess, but I'm thinking the end block with the nipple on it may also have a spring/piston thingy in there too, which dampens vibrations. This Nissan link suggests that http://www.zeroyon.com/index/content/view/32/47/

[Guest boostcut]

just a thourght but is the car really hot when it does this soft pedal trick?

[keeweechris]

 boostcut said:

just a thourght but is the car really hot when it does this soft pedal trick?

Thanks. Just normal operating temp. And its not the typical "soft pedal" issue here, its the opposite... "hard pedal". Here's my initial post again:

"Most of the time it works fine, but occasionally (once a week) something suddenly goes weird, and the hydraulic system shifts the contact-point of the clutch. Ie, the pedal goes hard, the contact point is near the top of the pedal travel, and pushing the pedal to the floor probably over-extends the clutch spring. Then say an hour later it returns slowly to normal."

[DRFVDR]

wondering if it a symptom of the actuating fork seizing on the pivot shaft ????

[keeweechris]

 DRFVDR said:

wondering if it a symptom of the actuating fork seizing on the pivot shaft ????

Yeah, I didn't want to think of that sort of thing until I absolutely had to :-\

If replacing all the hydraulics doesn't change it, I'll have to split the gb and have a looksie.

[rockr]

seal kits for both master and slave cylinder are available at bnt , peace of cake to bleed system, use a bleeding reservior for doing brakes, and take the slave of the g/box hold it with the nipple up , and hold the plunger in while ya get someone to slowly pump the clutch a few times, then tighten the nipple, the person pumping will have to pull the clutch pedal back up by hand , and remember to keep the reservior topped up with new clutch fluid.

doing it the traditional way by opening and closing the nipple will also work but very fiddly and messy

[keeweechris]

Turns out it was a stuffed slave cyl! It was sticking/jamming halfway through it's stroke. Not exactly sure how this was making the clutch pedal hard... but could have been stopping slave piston returning fully, then when clutch pedal returned the self-adjusting mech in master pumped new extra fluid into line which moved the contact point and prevented the master from reaching its self-adjusting point again, keeping pressure in the line.

I also replaced the network of hard line with a short simple line from a legacy, and bled it the way rockr said above. Easy-as, when the slave is higher than the master... all bubbles come out easily.

Below is a pic of the "damper system", if it is a damper system.

I was thinking, maybe it is trying to cancel out vibrations travelling up from the clutch to the pedal the same way mufflers and intake systems work. The 3rd leg of the hard line up to the bleed nipple could be tuned to reflect waves back to the main line, 180 deg out of phase, and cancel them out.

Whatever it was meant to do, it didn't do it very well, cos driving with the new simple pipe doesn't feel any different. Save yourself the hassle of bleeding 2m of tube, and swap to a simple pipe.

Thanks for everyones input.