Clutch issues, hydraulics?

[Santoku240]

Hello all.

I posted previously asking about replacement clutches, thinking that my current clutch is currently dying on me... but after a little test-driving tonight I'm starting to think otherwise.

Heres the deal:

I took the car out tonight, after tightening up my E-Brake cable (I tightened it up a good bit, but it still feels weak/sloppy, but thats a different story). And I noticed that my clutch WASNT slipping for once.

Intrigued by this, I went out on some back roads, and did a few light starts, no slip, I did some testing with it, starting at 2000 rpm in 2nd gear, stomped the gas, NO slip.

Normally the RPM needle would surge up a bit, meanwhile my speed would stay the same... but this time it was different.

So, further intrigued, I shift to 3rd gear, the gear that has been notorious for slipping (cuz thats where i spend most of my daily driving time).

2000rpm, stomp the pedal, pure acceleration, no slip.

HAPPY DAY! i think.

so i keep testing, no slip, no slip, no slip, no slip..... SWEET!

then i try a hard-shift.... 2nd to 3rd.

upon dumping the clutch, the rpms stay up at 4500, instead of dropping to like 2500(i think) or so like they should.

the cars speed kind of plataeus, and the rpms slooooooowly drop down, till i give it a little more gas.... upon which the RPMS raise, but the speed barely responds.

"DAMN" i think.

I continued various testing like this... and found that after a while, the clutch would slip even at the 2000rpm starting point with a good stomp on the gas.

Now, i havent paid too much attention to the conditions for slippage in the past, but i have noticed a very inconsistent, largely fluctuating amount of slippage. some days it holds like a champ, some days its a miricle if i can keep it from slipping with the most granny like driving i can possibly muster (trust me, i can drive like the slowest of them if need be :P)

My question is this:

If the clutch itself needed replacing due to wear, wouldnt the slipping be more of a consistent problem? These inconsistencies... could they be caused by the hydraulics?

I know for a fact that the seals are going, because the fluid in the master cylinder reservoir is turning black, and ive had to top the reservoir off once or twice in the last few months. Could leaky cylinders be cause to fluctuating clutch slippage? (i.e. not fully disengagin? air trapped in changing compressibility with temperature? anything?)

Thanks in advance for any responses

p.s. pardon any typos n stuff, its 4am over here and ive had an erratic sleep schedual for the last few weeks :P

[PapaSmurf2k3]

if it was hydraulics youd be able to feel it in the pedal, being sloppy/spongy, having the pedal engage higher/lower, or having it be weaker/stronger. whatever the case may be, it sounds like your in for a world of fun with your clutch system in the next couple of weeks.

[Ubernoober]

Possibly a few different things.

Oil on the flywheel. I rather doubt this one, but it tends to show some of the aspects of the problem you have. Clutch will also tend to "chatter" with oil on it.

Clutch hydraulics. Highly unlikely since these problems usually result in incomplete clutch dis-engagement, mushy pedal, and a pedal that sinks, not slippage.One possiblility in this regard are the flex lines swelling inside. This would cause fluid pressure to remain and apply force to the clutch. My only thought here would be... when was the last time you heard of swollen flex lines on your brakes, much less your clutch. It does happen, but very rarely, and really only with truly OLD cars (70's-80's). A final possibility here is a rusty slave cylinder. If the piston gets hung up on rust it could cause slippage. Since you are having to replace fluid, the seals somewhere are bad. Is it due to age, or a rusty slave? For the piston to get bound up would require a huge pile of rust. Pretty unlikely I think.

Clutch. Sadly, it sounds like this may be it. You didn't mention the miles on your current clutch, so I will just assume... a lot. This could potentially be bad news, but you won't know till you find the problem. Your symptoms almost exactly match what happened to me years ago. The cause: worn out disc. In fact, so badly worn, it gouged the flywheel. Here's the beef: Most clutch material is riveted to the disc. When you wear it down enough, you expose these rivets to contact. Since there is still friction material around them, at low power levels and daily driving, you engage normally. But when you apply more power, the loss of friction by having the rivets in contact with the metal of the flywheel or pressure plate is enough to allow the entire assembly to spin. Here's where it gets ugly. Normally clutches are designed to fail thin to the pressure plate side. Easy to replace, since it goes in with a new clutch anyway. BUT by the time you get to the conditions you mention, it has usually worn through on both sides. Thats expensive since you have clawed the flywheel up with the rivets. I hope it isn't this.

As an aside to your problem:As you slip the clutch and heat it up, you also lower the ability of the organic friction material to grip, thats why it slips more hot than cold. You are also glazing and overheating your pressure plate and flywheel. STOP DRIVING THE CAR. Whether you have a serious problem or not, by continually slipping the clutch you are GUARANTEEING an expensive repair. Just pony up the bucks for a new clutch if yours is old, and save yourself the expense of having to surface the flywheel, or even worse, buy new since you warped and cracked it.

Have fun out there.

[PapaSmurf2k3]

your supposed to re-surface the flywheel whenever you do a clutch job anyways. its not that expensive, i think mine was like $30 or so.

[navysnail]

how many miles does the clutch have?

[Santoku240]

Sorry about that, as far as i know its the original clutch that came with the car, and my odometer as of today is 99100miles(purchased at 73000mi).

I dont beleive ive noticed any chattering whatsoever in the engagement, so i guess that rules out oil being on it? a bit of a releif to me, as i dont fancy taking the oilpan off to replace its seal.

The fluid in the master/slave cylinders got low once which i noticed hardcore due to the pedal freeplay dropping to all the way but 1/2 an inch a few months back... thats when i started topping off the master cylinder reservoir.

The bit about the rivets has me a bit worried... but im guessing its best to get a new flywheel anyways, if i can afford it. speaking of which;

Whats the average going rate for a standard OEM replacement flywheel? I'm going to have to forgo my plans for a strong clutch and lightweight flywheel for now, in interest of affordability (currently between jobs )

Thank you all for your informative replies, your help is greatly appreciated

[SloS13]

2 friends of mine are having problems with intermittent slipping also. One guy removed his dampener and says the problem has gone away.

The other guy, we will prolly remove his dampener (they are bad about getting air stuck in there. I have to adjust his pedal every other day to keep it from slipping

[eddiec]

you could get a used flywheel for about 30-50 bux. add on resurfacing though.

i recomend removing the damper as well. youll have to reroute the hard line a little though.

have you bled the line in a while? i didn't read you doing that. also a new slave and master cylinder will cost about 40-50. or you could rebuild to the tune of about 20-30.

[Tx-Sx-FS]

i have a clutch problem/issue too...the pedal will go down..but is slow on coming back up...or will only come part way up and ill manually lift with my foot..im checking the slave cylinder tomorrow..but what else good it be?

[eddiec]

could be air in the line. after you check the slave bleed it really well.

also, my clutch return spring is a little weak. maybe yours is getting old to.

[Tx-Sx-FS]

thanks...il check it..is it hard to get to?

[eddiec]

clutch return spring? no its down there with the pedals. the hard part i hear is replacing it if its worn out. someone on here recently changed theirs and mentioned that it was a pain. but worth it.

however i would check to make sure your plumbing is not leaking then check the cylinders.

if that turns up ok it may be worth it to pull the transmission to inspect the clutch, if you have the resources.

[Tx-Sx-FS]

we blead the lines..worked better..but still slow to come up..or wouldnt come all the way up..ill have to check the spring tomorow.thanks for the help