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Henny

Golf IV 6 speed box clutch question....

3 posts in this topic

Right, I need some help.... (yeah, yeah, I know that many, many people have said that about me in the past! :P )

My 2003 Golf GTI 180bhp 20VT has an issue with the clutch hydraulics which I'm failing to get my head around and solve.

Back story:

So, the standard MKIV clutch pedal break happened to my car about 8 months ago where the welds on the bent metal "box" on the pedal which actually presses the plunger on the master cylinder snaps off.  I replaced the pedal and all the plastic bits and all was well and good again until about 2 months ago when the clutch pedal was pressed to the floor to change gear and didn't come back up again...  Having read up and investigated it, the clutch master cylinder had failed and so was replaced... Apparently this is common after the pedal fails as when it goes it bends the plunger on the cylinder (mine was bent in all directions!!!) and this caused the seals to fail.

I replaced the master cylinder with a brand new SACHS one and all was good for about 2 weeks when I noticed that the biting point was changing and getting lower and lower and the pedal felt spongy and just *wrong*... until at the end of a journey home, the pedal went to the floor without actually actuating the clutch.  I checked the whole system through and couldn't find any signs of leaks, so I bled it (Gunsons easy bleed, pressurised at 20psi) and it bled a lot  of air through... I'd read online that these can be a bit of a pig to bleed, so I rammed a litre of fluid through it and the fluid appeared well clear of air.  Tested it and it worked well and felt better than it ever had, so I was happy and thought that I'd sorted it......

Problem:

.....however, I now need to bleed the clutch hydraulics every 2 or 3 days of use as it keeps getting air in, meaning the pedal gets spongy, the biting point drops right down until the point where I the pedal doesn't actual activate the clutch....  Pumping the clutch 4 or 5 times  (raising it with my foot!) will let you get it into gear when stationary, so the car can be moved, but obviously this isn't great.   Sticking the easy bleed back on at 20psi shows no leaks and then bleeding out about 50ml of fluid will get rid of the air out of the system and get the clutch working fine again... once it's sorted, the car can be left unused and the pedal won't change, it's only when it's being used that it deteriorates.... :(

Questions:

So, the actual CLUTCH is fine, it's deffo the hydraulics that's wrong, so WTF is going on?!  Where is the air getting in?  The fluid level doesn't appear to be dropping AT ALL (marked it last bleed, and no visible change when it went wrong again), and there's no leaks of fluid visible?

This is the 6 speed gearbox with the clutch slave cylinder INSIDE the bell housing (so it's a gearbox off job to change/inspect it!), however the bleed nipple is BEFORE the slave cylinder, so if it was the slave, surely it wouldn't pressure bleed so quickly?

Anyone else ever come across this before?

Please help!?

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sounds like the clutch slave cylinder is leaking inside the box fella

 

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nope, it's the O ring on the pipe from the master output.... it's not leaking fluid from anywhere when you press the pedal, but it's pulling in a tiny bit of air when you release it... over time it's enough that you lose the pedal completely... Bleed it, and it comes good again....

With where the bleed nipple is in relation to the slave cylinder and where the air is in the system (between the bleed nipple and the master cylinder, not past the bleed into the slave) that's the only place it can be unless I have a duff new master cylinder....

I've got the parts to fix it, (sub £10!) but I haven't had chance to do it due to building work at our house at the moment taking priority....  It'll get done shortly and then it'll be up for sale.... :)

 

Ta for the thoughts though... :)

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