When i drive the car for more than 25 mins, the clutch engagement point gets higher and higher in the pedal travel. When its over-night-cold the engagement point is just off the floor but a reasonable distance. just kinda "quick".

I once had the engagement adjusted so it was a little more in the middle when cold and it caused the clutch to slip when hot.

any ideas here? im thinking maybe a bad master cylinder seal but the fluid level hasnt changed and it has good pressure in the pedal.

 

Sounds like air in the lines to me. Bleed your clutch.

 

its not air in the lines. the pedal feel would change with that and the fluid level would be changing.

 

That is usually true, but not 100% of the time. Right before replacing both my Master & Slave Cylinders last week, the Disengagement point was too low in the pedal travel, yet remained relatively consistent and unable to put the car into gear while idling. This meant the Slave Cylinder wasn't moving as far as it should to disengage the clutch.

Given the propensity for one device being replaced to cause the other to fail, it is good practice to replace both at the same time. My MC was old and the SC was old and from an unknown source, so I replaced both

My gut feeling says that either your clutch fluid has absorbed too much moisture and needs replaced or the hydraulics are drawing in air on the upstroke (when you release the pedal). Now's a good time to invest in a M7x1.0 speedbleeder too, it turns the long 2-person PITA called bleeding the clutch into a 5-minute one-person joy that works really well.

 

not a bad idea about the speed bleeder.

im positive its not moisture or air. if it was air like you said, it would engage very low but likely wouldn't change position with heat.

i think the MC might not be sealing properly when cold and when hot seals up causing the catch point to rise with heat.

 

Your issue sounds like something mine had before I changed the clutch. The old disc was 6.6mm thick and would engage higher and higher the hotter it got. The pressure plate spring fingers were very lifted as you can imagine. Also turns out my clutch master had a plastic piston that was getting kinda stuck in the bore. That is common with plastics as they are not self-cleaning unlike the aluminum type which scrape the bore every time and keep it clean.

Fast forward to just this Saturday. Did a quckie rebuild of the clutch master to stretch the spring out and hone the bore a little so the plastic piston returns back out to its normal resting place. Also swapped in a freshly resurfaced flywheel, new stock disc and a healthy low mile nearly new pressure plate. Now the friction point is adjusted right where it should be and engages perfectly, and seems to hold steady from a cold startup to fully warmed up.

How old is your clutch disc? Did your master have a plastic piston? Or metal? By the way, mine wasn't losing fluid either.

 

I don't understand, the piston- be it plastic or metal- runs on a seal, if it's "scraping the bore", something ain't right.

 

i think maybe you have the NA slave on the turbo gearbox?

a known clash where it will ride the clutch slightly
you can bandaid it by shortening the slaves rod

ultimately using the turbo slave fixes the issue
( different relative positions on each of the slaves mounting lugs )

 

ok then I'll state it a different way. I've come across two master cylinders that had plastic pistons and several others with metal pistons. The two with plastic pistons had problems getting stuck inside the bore while the metal ones didn't. This usually shows up after they sit for a while.

As for scraping the bore, I'll restate that as well. I had one where the clutch pedal was just a little bent. This put a side load on the piston as the rod wasn't going in perfectly straight, and it was literally scraping the bore every time and wore it down (the aluminum piston, not the harder iron material). It eventually leaked due to this. The new master has a metal piston and I can see how much the pedal needs to be bent to get it back in line.

 

was this in response to my issue? if so how can you tell which slave is for which? seems to me that most manufacturers dont make a distinction between turbo and na slave cylinders


the clutch i THINK is original. so its likely that its just worn out and needs to be replaced. however im not gonna do it until it starts slipping. i have 0 desire to do that job.

 

yes,, the response of someone who has been there seen that.. the NA and turbo slaves have different slave mounting points and different throw rods

and it will and does cause this issue where it is fine cold,, but rides hot

if you have the NA slave
.. pull the rod and take 10 mm off the rounded end ( and round it again on the grinder ) till you can physically wiggle the slave rod when it is fitted

 

yah i think you are right about the cold statement. i doubt this is it too. btw, shouldn't i be able to test which slave i have by checking for play in the rod when the clutch is not engaged?

also im leaning towards a MC issue or outright needing a clutch.

 

UPDATE!!!!

as it turns out lots of DSM buys have problems with this and it has to do with how the master cylinder is deigned. Its called "Clutch pump up" and its exactly like any other hydraulic pump-up issue. Its also not related to heat but related to clutch usage, thus why it wasnt doing it to me on long freeway commutes but WAS doing it after running errands (city traffic).

That statement about heat vs usage didnt actually occur to me until i read about the scenarios that cause it and when it happened to me.

apparently the DSM solution is to adjust the clutch stop at the top of its travel to allow even more travel. I have not yet done this but im going to give it a shot since its a free solution.

 

It's leaking internally. It usually happens with old cars. Especially when guys install a heavy duty clutch disc. A good test to run is with the engine off hold the clutch to the floor and at least 1 full minute. If the pedal fails to return to the up position on it's own then it's time to replace it.

 

Replace what, the pedal?

 

yah i confirmed whats going on today.


I adjusted the pedal freeplay so there would be more travel upwards. i did this by backing the clutch stop, which is effectively the neutral safety switch a little ways. I still got some pump up. so i pulled up on the pedal with my foot and it all "drained" and went away immediately.

im thinking i need more adjustment and i cna dial this out. It might also be partly that i need a new master cylinder but im going to see if adjustment will work first. since its free.

 

Most likely a lip seal on your master is starting to fail. As you mentioned, temperature, a butterfly fart, or anything might cause it to work one day and crap on another. The Master is pretty cheap. I would go ahead and do the whole system and be done with it.

 

if the seal was failing the master would make no pressure or little pressure.

this is the opposite case

 

Messing with the adjustments at the pedal or grinding down parts to make problems go away is a Band aid solution at best. I would get a rebuilt master and slave and maybe replace the old rubber hose and be done with it.

You want a certain pedal free play and a certain pedal height as per FSM for proper function and parts lifespan. I.e. no free play, less release bearing life, more pressure plate finger wear.

 

again, that would be adjusting it the opposite direction of what i did/am doing.

 

Yea, and everything attached to it. From the rubber to ya brain.