16 replies to this topic

[rally1380]

Hi.

 

As always on the week leading up to a rally the car has decided to get nervous and have a problem!!!

 

Clutch won't allow me to engage a gear - or it will, but only with force and then with the clutch pedal still down it is dragging.

 

Clutch pedal is a bit spongey at the top of travel so assume air is getting in somehow.

 

How can i tell if it is the master or slave cylinder at fault????

 

No fluid is being lost which is the normal indicator that the master has corroded and fluid is leaking past - and no fluid on clutch pedal either. 

 

When i ask my assistant (wife) to put her foot down on the clutch, then place a screwdriver between the throw back bolt and the lever, then when she pumps again the lever moves a bit more - probably the 'bit more' i need.

 

The slave cylinder bleed nipple was loose ish in its hole and i suspected this was leaking fluid in so wrapped it in PTFE and put it snuggly back in and it did seem to solve the issue at first, but now the clutch isn't working again.

 

Obviously i can go out and buy a slave cylinder tomorrow and fit tomorrow night BUT if it is the master i need to get one ordered ASAP as i've got scrutineering Friday night!!!!

 

Any advice or hints....???

 

 

[cambiker71]

Sounds like it might have a bit of air in the system, have you tried rebleeding it? 

[cambiker71]

Ptfe tape round the nipple won't help, it seals on the tapered bit at the end!

[rally1380]

Ptfe tape round the nipple won't help, it seals on the tapered bit at the end!

 

What i was finding was that when seated the taper was sealing and holding ok, but when the bleed nipple was released to bleed the thread was so loose that air got down the thread and past the seat - so just let more air in (if that makes sense?)

 

The PTFE was purely to stop this happening.

 

Definately air in the system though - just need to work out from where.

[cambiker71]

Do you have a spare washer bottle and pump laying around?

If so fill it with brake fluid and bleed it backwards from the slaves bleed nipple, just watch out for the reservoir filling up and overflowing, a 15 second working of the washer pump will usually be plenty to bleed it out properly!

[rally1380]

Do you have a spare washer bottle and pump laying around?

If so fill it with brake fluid and bleed it backwards from the slaves bleed nipple, just watch out for the reservoir filling up and overflowing, a 15 second working of the washer pump will usually be plenty to bleed it out properly!

 

I bled it with an eezibleed (or however you spell it) last week and that worked ok. Then went for an MOT on friday and the tester said it was a bit spongey so bled it again this weekend and now the problem has occured.  I would have thought the eezibleed would have forced all the air out nicely......and no i didn't use a tyre over the recomended PSI and yes it has worked fine before

 

Old cars eh! you just can't beat em!!!!

[cambiker71]

They're ok to use usually but the washer pump through the bleed nipple is easier if you have one!

[rally1380]

I do actually as i got a double delivery of one when postman pat lost it then found it.  Will give that a bash, but going to get a new slave cylinder tomorrow anyway as i'm sure that bleed nipple wobble is causing the issue.

[cambiker71]

Try back bleeding it first though, I doubt the nipple is the problem, once it's tight it makes no difference to the system if it's not leaking fluid.

[cambiker71]

Just make sure the washer pump is connected to a 12v feed or a spare battery the right way too, you want it to fill the system from your spare washer bottle through the bleed nipple from bottom to top, not suck fluid from the bleed nipple.

If you can, drain some fluid from the reservoir first to stop it overflowing, good luck!

[minimadles]

Try removing the pipe from the master cylinder put a bleed nipple directly into the master cylinder bleeding it through the pedal should then be solid leave it for an hour or so then retry Any movement in the pedal then points to the master cylinder been at fault as you have removed the slave cylinder from the equation. Usually though if the master cyl is at fault the pedal remains spongy even though it's isolated totally from the slave

[rally1380]

Try removing the pipe from the master cylinder put a bleed nipple directly into the master cylinder bleeding it through the pedal should then be solid leave it for an hour or so then retry Any movement in the pedal then points to the master cylinder been at fault as you have removed the slave cylinder from the equation. Usually though if the master cyl is at fault the pedal remains spongy even though it's isolated totally from the slave

 

Cheers...nice idea and that will certainly eliminate the master if all is well.

[Gr4h4m]

In my experience it's normally the slave that goes more than the master. They seem to get a bit of rust in the bore. I was doing 1 a year after it had been stood over winter. I have seemed to fix it but only by swapping the slave for a force racing billet slave. Never had the issue since.

[rally1380]

I think (emphasis on 'think) i've solved it, but was unable to fire the car up and check that i could engage a gear as it was late and although i'd love to wake my neighbours up, my wife would have my gonads for ear rings!!!

 

Did a mixture of 3 things -

 

I had a spare syringe (as you do) so connected a pipe to that and forced fluid back up through the system into the master - was going to use my spare washer motor as suggested above but then it would be full of brake fluid so figure a free syringe is a better method.

 

Next I slackened off the throw back adjusting bolt and screwed it in a bit and then gave the slave cylinder a good pump with my hand and at the same time released the bleed nipple.

 

Next I put a tube on the bleed nipple and sucked at the tube whilst cracking the bleed nipple off.

 

Fingers crossed all air is now expelled but i do suspect the bleed nipple is where the issue is starting as it is letting air in down the threads when bleeding.....so i'm getting a new slave cylinder anyway as a spare is always handy and that way if i get home from work tonight and the clutch is still not playing ball then i can at least change the slave pretty quickly and check that off the list.

 

Cheers for all the advice peeps....will update later with if i've got gears!!!!

[Gr4h4m]

How did it go? I have a spare brake master but I don't thing you can use them for the clutch?