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Technical  Repeatedly bleeding clutch

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Technical  Repeatedly bleeding clutch

schumraid

schumraid

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Hi guys,

Over the course of the past few months I have had to bleed my clutch several times and every time I do it the interval before third gear becomes sticky (this is the where it is most noticable) gets a little lower.

I have done a full system bleed at the brake calipers then just been bleeding at the slave cylinder every month or so but this time the silky smooth gearchanges have only lasted for a few days.

My brakes are not spongy, I can't find any leaks and the brake fluid resevoir hasn't moved anyway. My clutch bite point keeps moving slightly but unless I really abuse it (dump the clutch from high rpm at a standstill, something I'm not a fan of doing by the way) the clutch doesn't slip and in this case I would forgive it for doing so anyway.

I'm stumped, any ideas what could be causing this? Short of a new clutch and/or gearbox oil I'm confused!

Cheers!
 
When was the fluid last changed? Brake fluid absorbs water, after 2 - 3 years it should be changed otherwise the water is turned into vapour by the heat generated by braking.
 
Ffoxy said:
When was the fluid last changed? Brake fluid absorbs water, after 2 - 3 years it should be changed otherwise the water is turned into vapour by the heat generated by braking.
Click to expand...

Good call, I was thinking on a much larger scale (new gearbox etc) and didn't even consider the fluid. I've had the car for nearly 2 years and the fluid hasn't been changed in that time so that's a job for today :D.

What's the best way to get all the old clutch fluid out? Should I be pumping the clutch with the pipe off at the slave cylinder in the same way that you do the brakes?

Cheers!
 
As your bite point keeps moving but your brakes feel solid, you're not losing fluid and bleeding clutch cures it for a while then the more likely cause is a problem with your clutch hydraulics

NO 1
If your pedal is not returning to the fully up position and getting a fresh shot of fluid from the reservoir then this means as the clutch fluid heats up with use then the bite point moves down and down. Next time it happens, put your foot under the clutch pedal and drag it up, if the bite point now moves back up again then there's your problem

No 2
If you have an internal clutch slave cylinder then it's easy to not notice that the slave is leaking as it's in the clutch housing, the small amount of fluid loss is hardly noticeable in the hydraulic reservoir level but it's more than enough to ruin the clutch hydraulics operation. Only cure is a new slave cyclinder but as you haven't told us what engine you have then you may have an internal or external cylinder and the external one leaking is easy to spot

To bleed the system then by far the easiest is to use a one man bleed kit, it's similiar to how they do it in garages, by puttiing a small pressure directly on the master cylnder reservoir with a constant supply of fluid then you simply open the bleed valves until good fluid pours out with no risk of pumping air into the system. You'll find it's handy for pressuring your coolant system for leak checks too
 
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Decks,

Sorry, I have the 1.6. It's very hard to describe exactly what happens, it just kind of feels like it needs bled (bite point going low) and a slightly sticky gear change.

When the bite point moves I wouldn't have time to get my foot under the pedal, it's a split second thing and almost feels as if the clutch plates are sticking in place before clunking slightly back together, if that makes sense.
 
Do you feel there is growing gap between the pedal being fully up up to finally starting to move the master cylinder, that disappears after bleeding or leaving the car still for a few hours, like in the video below? Does your bite point move up and down when driving the car, always getting worse until you leave it parked for a few hours?

I've also put some nice music so you can relax until we try to help you fix your problem. :p

 
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Ha! I remember that one Vladof:)

Minus8, with a 1.6 then things are much easier as you have an external slave cylinder. If it's leaking then there will be fluid in the protective boot where the slave cylinder push rod goes through so give it a squeeze and if it's full of fluid then the slave cylinder seals are gone

When the bite point moves I wouldn't have time to get my foot under the pedal, it's a split second thing and almost feels as if the clutch plates are sticking in place before clunking slightly back together, if that makes sense.
Sure, but when the clutch is playing up and you've finished your gearchange, put your foot underneath the pedal and drag it up and then try it, if it's ok then it'll more likely be a problem up at the master cylinder end as Vladof had
 
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Deckchair5 said:
Ha! I remember that one Vladof:)

Minus8, with a 1.6 then things are much easier as you have an external slave cylinder. If it's leaking then there will be fluid in the protective boot where the slave cylinder push rod goes through so give it a squeeze and if it's full of fluid then the slave cylinder seals are gone

When the bite point moves I wouldn't have time to get my foot under the pedal, it's a split second thing and almost feels as if the clutch plates are sticking in place before clunking slightly back together, if that makes sense.
Sure, but when the clutch is playing up and you've finished your gearchange, put your foot underneath the pedal and drag it up and then try it, if it's ok then it'll more likely be a problem up at the master cylinder end as Vladof had
Click to expand...

With you now, I'll get investigating, thanks for the advice :)
 
Yes I thought it would bring back memories. :p Boy I tried everything on that car and then just changed the master cylinder and those were the best spent 70 pounds. :) Mine never did give away like that, it was always doing the same thing and was never bad enough to grind just awful to drive because I pushed the pedal one way when first starting the car then slowly degrading while driving ending up in stalling the engine because the bite point was up and low, up and low.

If you have a lot of debry in there it may act as a cork preventing any fluid from reaching the cylinder thus blocking the whole pedal.

And trust me, mine was really really bad, I could hardly blow any air in there. It's not worth cleaning it because you can never really do a good job, just buy a new one and fit it and you'll find the car drives like a dream after that.

Try Decks's advice, pulling the pedal up should force liquid in the cylinder unblocking the clutch.

attachment.php
 
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vladof said:
Yes I thought it would bring back memories. :p Boy I tried everything on that car and then just changed the master cylinder and those were the best spent 70 pounds. :) Mine never did give away like that, it was always doing the same thing and was never bad enough to grind just awful to drive because I pushed the pedal one way when first starting the car then slowly degrading while driving ending up in stalling the engine because the bite point was up and low, up and low.

If you have a lot of debry in there it may act as a cork preventing any fluid from reaching the cylinder thus blocking the whole pedal.

And trust me, mine was really really bad, I could hardly blow any air in there. It's not worth cleaning it because you can never really do a good job, just buy a new one and fit it and you'll find the car drives like a dream after that.

Try Decks's advice, pulling the pedal up should force liquid in the cylinder unblocking the clutch.
Click to expand...

I remember driving my dads car when the master cylinder packed in and I know exactly what you mean, it just doesn't feel the same but as you say it could just not be as bad as yours yet.

I'm off to work now so I'll have a little play and post back with my findings tomorrow.

Thanks again guys (y):)
 
There isn't really anything to wait for, the bite point moves but it's over a longer period of time that it moves, when I bleed the clutch the biting point returns to a semi high position then slowly moves down over a few weeks.

Even when the bite point is close to the floor everything still feels solid ie like a cable operated clutch that needs adjusted

Hope this makes sense!
Cheers
 
Sorry, I didn't realise you were waiting for approval, feel free to carry on without me ha!:)
It could be a slave cylinder leak but the fluid has to leak somewhere so have you checked the bellows type gaiter at the end of the slave cylinder for fluid? It should be full or traces of a hyd fluid leak on top the gearbox there. If there's no leak then it could just as easily be the master cylinder. When the slave cylinder leaks the clutch pedal doesn't return to the fully up position as it relies on fluid pressure to push it back up but the same can happen at the other end so check for leaks either at the slave cylinder or on the mat under the pedal

I can make those same symptoms happen by preventing the clutch pedal from getting fully up but as long as you're sure that the pedal IS returning to the fully up position and nothing is preventing it doing so then we can eliminate that
 
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