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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Mon Jun 05, 2017 4:20 pm    Post subject: Clutch Hydraulics issue Reply with quote

Hello, wondering if anyone has any experience with the following?

The clutch slave cylinder hose gave up recently and along with replacing it I decided to do the slave and master cylinder at the same time.

Bled the fluid through using a Gunsons power bleeder, using about 20 psi from a tyre. No bubbles, so thought it was OK. Felt a bit weird though. Light and inconsistent.

Since then it's got worse, with gears hard to select, indicating clutch drag, but full engagement appears fairly high up.....

I've tried bleeding it through again but to no avail. I got a bit better function, but within a few miles, it went rubbish again.

Any ideas?

Air in system? Seemed OK with no bubbles etc...
Dodgy master or slave? - thinking of trying to put one of the old ones back on.....

Many thanks, Jim
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Demort
Paul Ricard


Joined: 21 Mar 2015
Posts: 3113
Location: Sussex


PostPosted: Mon Jun 05, 2017 8:01 pm    Post subject: Reply with quote

Ive got to admit ive struggled at times bleeding these systems .. i had a pressure bleeder and someone pumping the pedal on the last one i did .

But .. i found with air in it the pedal sits lower and the biteing point is on the floor .. yours doesnt sound that way .. booster spring perhaps or just a fault in one of the components you have fitted sounds a bit more likely .

Try to get someone in the car and rapidly pump the pedal , hold it down then do a bleed then repeat with your pressure kit fitted just in case it is air in the system .
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Mon Jun 05, 2017 9:14 pm    Post subject: Reply with quote

Thanks Demort,

I'm thinking it is air in the system, as I got it better with pumping the pedal rapidly whilst the pressure bleed kit was fitted, but it got worse again quickly.

The booster spring doesn't help as it sticks the pedal down. I might try taking it off, and doing as you say, hook up the pressure bleed kit and bleed the system while someone works the pedal.

I'm loathe to swap components back again, but may have to if that doesn't work. Any other things to try? It doesn't seem likely that the booster spring would make engaging gear difficult would it? There is full range of movement of the pedal.

Cheers
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Demort
Paul Ricard


Joined: 21 Mar 2015
Posts: 3113
Location: Sussex


PostPosted: Tue Jun 06, 2017 8:07 pm    Post subject: Reply with quote

You could also try a vacum system on the slave and a pressure one on the master cyl .. basically anything to force the fluid through .. my opinion is that air doesnt like going downwards on these systems so needs an awfull lot of help Smile

i guess jacking up the back end might help .. not something ive tryed though

You have to use your hand on the clutch pedal as it will stick down otherwise with the booster spring pressure .. as you already know Smile

It does sound more like air though rather than something thats faulty .. pumping up the pedal is the clue ...
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Tue Jun 06, 2017 8:13 pm    Post subject: Reply with quote

Good idea Demort.

I'm having another crack at it on Thursday. My driveway is sloped. I'll try getting the back end as high as possible and keep going with pumping the pedal, holding it down then bleed. And repeat......

Cheers
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Thu Jun 08, 2017 1:41 pm    Post subject: Reply with quote

Grrrrr!

Bled it again, and again and again. No real improvement. Found I've thrown the old master cylinder away - typical!

Changed the old slave cylinder back in..... no improvement and exactly the same. Another new master cylinder on order. Eurocarparts will accept the old (New) one as a return.....

Try again Monday. If that doesn't work, it may be new clutch time.

Cheers
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BHZ661
Österreich


Joined: 03 Feb 2015
Posts: 980
Location: Milton Keynes


PostPosted: Thu Jun 08, 2017 1:53 pm    Post subject: Reply with quote

Im sure when i bled mine it was with peddle down , while being pressurised
 
  
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Thu Jun 08, 2017 2:58 pm    Post subject: Reply with quote

Hi, yes your right.

I found a rennlist post, and the Bentley manual says the same thing. I'm confident now that the air is out, but the clutch is still weird and inefficient.

Definitely drag stopping static gear engagement. Pedal takes a loooonnng movement back to allow the clutch to fully lock up again..

Now got to try a new master cylinder....... If it works, maybe refit the new Slave too....
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Mon Jun 12, 2017 5:53 pm    Post subject: Reply with quote

New Master cylinder fitted.

Definitely better, but still not quite as good as before all this started.

Out testing today, 4,000 rpm long uphill in 4th gear, as I accelerated hard the revs flared, tried again, clutch slipped again.....

Ahhh! maybe not completely down to hydraulics then.

Is anyone able to help out with symptoms of worn clutch?

Biting point is near the floor, but fully engaged point is middle to end of travel upwards. Clutch appears to drag, making gear selection difficult from standstill too.

Best price I can see for LUK flywheel, and Sachs clutch kit is £532 on ebay. Anyone know any cheaper anywhere? Tried Design911 and Eurocarparts already....

Cheers James
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Demort
Paul Ricard


Joined: 21 Mar 2015
Posts: 3113
Location: Sussex


PostPosted: Mon Jun 12, 2017 7:38 pm    Post subject: Reply with quote

Out testing today, 4,000 rpm long uphill in 4th gear, as I accelerated hard the revs flared, tried again, clutch slipped again.....


Thats the symptoms of a worn clutch or oil contaminated .

I cant see how anything you have changed would hold pressure on the hydraulic system .. and indeed ive never seen it .. well .. on a modified system where the master cyl rod was too long but that was a brakeing circuit .

Biteing point is normally at the top for a worn clutch though .. maybe more than one fault here Question
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Mon Jun 12, 2017 7:55 pm    Post subject: Reply with quote

Hmmmmm,

Difficult to explain, I can feel the release bearing spinning through the pedal as soon as I start to depress the pedal. The clutch doesn't release till over halfway down then never appears to fully disengage from the flywheel (drags very slightly).

On the way up, the drive picks up very near the floor, but then takes a fair bit of travel upwards till it's engaging fully again. There is then a stage where the pedal almost stops on the way up (coinciding with full clutch engagement) then overcomes the booster spring to come fully up.

Beats me! Quotes for the lot being replaced are £1500 in RMS ims cover, and flywheel.
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tims1959
Trainee


Joined: 15 Feb 2009
Posts: 97



PostPosted: Mon Jun 12, 2017 7:56 pm    Post subject: Reply with quote

James,
Mine's a 997 but basically the same. I had exactly the same clutch slip problem, which was cured by bleeding the clutch system through.

I happened to be on a road trip in Norway at the time, clutch started slipping under load in 5th, bite point very high.
The Porsche centre in Oslo were very helpful, they fitted me in on the same day but their service manager told me I'd burned out my clutch.

However it was only a year old and had been fine until the day before, so I asked them just to bleed the clutch.

They hooked up their machine and thoroughly bled the clutch and the brakes, and that did fix it 100%.

I did subsequently change my master cylinder but when I did I made sure I bled it through twice (I've just got a sealey pressure bleeder).

10,000 miles and two years later it's on the same clutch and still working fine.

So in my diy experience, air in the system plus high temperatures and hard use can definitely push the release bearing out enough for the clutch to slip, even with a new clutch and flywheel.

I've never experienced any clutch drag but I'm sure if there is *any* air in the clutch hydraulics it can cause both drag when cold and slipping when hot.

HTH

Last edited by tims1959 on Mon Jun 12, 2017 8:44 pm; edited 1 time in total
 
  
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Mon Jun 12, 2017 8:28 pm    Post subject: Reply with quote

That is very reassuring news, many thanks for that.

I am at my wit's end bleeding the thing myself! Ive got the Gunsons eezybleed kit pressured at 20psi and recycled the fluid about 10 times now.

Based on your experience, I will get the garage to have a go. It's in for MOT on Monday I'll see if they can have a go then.

Thanks again for your post
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tims1959
Trainee


Joined: 15 Feb 2009
Posts: 97



PostPosted: Mon Jun 12, 2017 8:52 pm    Post subject: Reply with quote

No worries, I hope you get it sorted out. As it was all ok before you swapped the hose it sounds like what happened to me (I had renewed the slave cylinder just before the road trip I mentioned).

While you bled the clutch with your pressure bleeder, did you also depress and release the clutch pedal by hand?

Demort would know better than I do but according to the service manual for the 997 you need to do that as well as letting fluid run through.

You need to move the pedal gently by hand, because unless you hang onto the pedal the clutch helper spring will flip the pedal right down to the floor.

Good luck with it
 
  
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Jamesx19
Monza


Joined: 10 Jul 2015
Posts: 183
Location: Brighton


PostPosted: Mon Jun 12, 2017 9:59 pm    Post subject: Reply with quote

Hi, yes, bled it with the pedal on the floor, then worked it up and down gently around 10-15 times. No difference in feel between start and finish of that though. Then locked pedal down again, bled it again, worked pedal again, no difference though.

Local mechanic suggested the bleed hose needs to loop up higher than slave body, before going down into catch jar on account of the side take off bleed nipple as opposed to a top mounted bleed nipple.

Think I'm done with 'one man' bleeding myself. I've tried gentle pedal pumps, rapid pumping of the pedal, bleeding with pedal down, bleeding with pedal up!!!!!

I'll see if garage can have a go. I will show them your post though.

Cheers
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