Clutch Problems 1.8t AUQ

[SlashProm]

Hey guys. I've been having some problems with my Clutch pedal dipping down to the floor. Clutch has been feeling heavier and so on. I have since removed the gearbox, changed the clutch, pressure plate and concentric slave cylinder. Bled the slave with a gunson easy bleed and everything is great. Clutch pedal is really light, and smooth, feels 100x better. The problem.

I went for a drive to the shops to test it out. When I braked for the junction to the main road the clutch pedal dipped and I had to pump it a couple of times to get the pedal back. I was thinking maybe I need to bleed the brakes but I don't understand why the brakes would effect the clutch system when they only share a reservoir and the reservoir is topped up.

Am I right in thinking this is just a coincidence and that my Master cylinder is dying and allowing fluid to leak internally past the seals causing pressure loss. Or could bleeding the brake system actually make a difference on these cars?

PS: Car was just up to temp and was braking gently to get out of my estate, over speed bumps, around parked cars etc, so it is definitely not overheating fluid in the braking system. Thanks for reading, I look forward to your expertise and replies.

PPS: I've found this Master Cylinder. https://www.onlinecarparts.co.uk/valeo-13777090.html seems to be right, would anyone have a part number so I can look around and be sure it's the right one. Would be helpful if I don't have to strip the old one to get the right part number. Thanks.

 

[bruceR]

The clutch hydraulics are part of the same system. Would be a good idea to at least bleed the master cylinder


Sent from my iPhone using Tapatalk

 

[SlashProm]

Thank you, makes me feel a little bit more hopeful. So is there a bleed valve on the clutch master cylinder around the pedal assembly? Or are you saying there may be air in the brake master cylinder causing problems?

My wife is picking me up some dot4 while she's out getting a few supplies. I'll get the easy bleed out and flush a couple of litres of fresh fluid through the brakes and let you know if I get a chance to test it local tonight. I'm hoping it's not the master cylinder but at least it's not as bad as doing a slave on your own in the car park

 

[bruceR]

IIRC there is 1 bleed nipple on top of gearbox just under battery tray, 2 bleed nipples on master cylinder (RHS as you look at it) then the usual ones on each brake caliper.


Sent from my iPhone using Tapatalk

 

[SlashProm]

Thanks. I've done the slave again. For some reason the back brakes are taking a while to bleed. I have the eazy bleed hooked up to the spare at around 20 psi, but barely any fluid coming out of the backs. Pumping the brake pedal gently while the bleeder is on is forcing it through slowly though. I'll do the fronts and then the master and get back to you, thanks.

 

[SlashProm]

Update. I've bled the brakes and the clutch at the slave again. No air in there. I've noticed a hissing sound when I pump the clutch, I'm not losing fluid and no visible leaks anywhere. Am I right in thinking the Clutch Master has failed internally? I assume if it was leaking from the fittings to the master that I'd see fluid coming out, or at the bare minimum be drawing air into the system.

 

[mty12345]

Very much sounds like the clutch master cylinder has failed to me, although obviously it's hard to be sure. I agree with what you said, if you had a leak then the fluid would drop and you'd see it. I guess the only other real possibility is that the new slave cylinder was faulty when you bought it.

 

[SlashProm]

Ok. I'm totally lost. I've replaced the Master and Slave and I'm still having problems. The clutch bleeds just fine with the ez bleed. I can also sit there and pump the clutch 1000 times and it holds pressure. As soon as I go for a drive down the road it just keeps dipping down and losing pressure, give the clutch pedal a kick and it bounces back up again and it's all fine. I don't understand why it's doing it. All I can think is that the bleed valve needs replacing. I've noticed that if you wiggle the nut you can see a little fluid underneath the nut that the bleed valve screws in to, but it doesn't come out, it's just wet in the grove around the nut.

I tried to bleed the clutch manually after the ez bleed just for piece of mind earlier, I got my wife to hold the pedal to the floor while I loosened and re-tightened the bleed valve. All I was getting was fresh fluid and no signs of any air. Then all of a sudden my wife said that the pedal wasn't coming up, like she'd pulled it up with the valve open, which she hadn't, then I went to bleed it again and all I got was squirts of air followed by no fluid and couldn't get pressure back. Like the slave was now full of air, and I had to get the ez bleed out again. It's confusing the hell out of me.

 

[Rich76]

Ok. I'm totally lost. I've replaced the Master and Slave and I'm still having problems. The clutch bleeds just fine with the ez bleed. I can also sit there and pump the clutch 1000 times and it holds pressure. As soon as I go for a drive down the road it just keeps dipping down and losing pressure, give the clutch pedal a kick and it bounces back up again and it's all fine. I don't understand why it's doing it. All I can think is that the bleed valve needs replacing. I've noticed that if you wiggle the nut you can see a little fluid underneath the nut that the bleed valve screws in to, but it doesn't come out, it's just wet in the grove around the nut.

I tried to bleed the clutch manually after the ez bleed just for piece of mind earlier, I got my wife to hold the pedal to the floor while I loosened and re-tightened the bleed valve. All I was getting was fresh fluid and no signs of any air. Then all of a sudden my wife said that the pedal wasn't coming up, like she'd pulled it up with the valve open, which she hadn't, then I went to bleed it again and all I got was squirts of air followed by no fluid and couldn't get pressure back. Like the slave was now full of air, and I had to get the ez bleed out again. It's confusing the hell out of me.

Yes, it does sound strange, but surely the bleed valve is part of the new slave cylinder? it shouldn't be giving problems.Unless the new cylinder is faulty logically the fault must be in the pipe from the master cylinder.I have come across this a few times in other cars, like recently on a mate's Astra.

 

[SlashProm]

It has a Concentric slave, the end of it comes through a hole in the gearbox near the starter, from there you clip on a plastic t piece with the bleed valve and then it's a section of rubber hose, to metal lines, then some weird looking regulator on the bulkhead and along into the master on the pedal. I can't see any leaks anyway and don't seem to be losing any fluid, but air must be making it's way in to the system somewhere.

 

[Rich76]

OK, well I would say air is getting in either through the plastic t-piece or more likely from my experience, the seals on the rubber pipe.I think I would replace the plastic anyway because the plastic used on parts like that breaks quite easlly and gets more brittle with age.I really don't like tightening bleed nipples on something like that!

 

[SlashProm]

I've had my ez bleed hooked up to the reservoir with a little over 20 psi on it for about 10 minutes now. Not a drop of fluid leaking out anywhere. I don't get this car, it's got a new master and slave and no signs of any issues. How can it let air in so easily but wont let a drop out at over 20 psi?

I think I'm just going to have to replace the t-piece. I can't see anything leaking out, but what I have noticed, is that when you bleed the slave at the t-piece and tighten it back up. Fluid is obviously right up to the top of the nipple. I've just come back to it about 30 minutes later and the fluid is almost gone from inside the nipple. Although very slow and not leaking outwards under pressure. It must be drawing air in here as it's the only explanation for the fluid disappearing from the bleed nipple

 

[Rich76]

I've had my ez bleed hooked up to the reservoir with a little over 20 psi on it for about 10 minutes now. Not a drop of fluid leaking out anywhere. I don't get this car, it's got a new master and slave and no signs of any issues. How can it let air in so easily but wont let a drop out at over 20 psi?

I think I'm just going to have to replace the t-piece. I can't see anything leaking out, but what I have noticed, is that when you bleed the slave at the t-piece and tighten it back up. Fluid is obviously right up to the top of the nipple. I've just come back to it about 30 minutes later and the fluid is almost gone from inside the nipple. Although very slow and not leaking outwards under pressure. It must be drawing air in here as it's the only explanation for the fluid disappearing from the bleed nipple

Yes try replacing that first then the rubber pipe if necessary. There could be a tiny crack in the plastic or something. It will be interesting to find out the cause of your problem. Although it doesn't seem possible that a part can not leak fluid under pressure, but let in air, it does happen.

 

[SlashProm]

May have found the problem. Will update later. I pulled the Bleed valve assembly out of the T-Piece and found a small nick on the inner edge of the o-ring that seals the Bleed valve. This may also explain why it lets air in but not fluid out, as it's such a small nick in a rubber o-ring.

 

[mty12345]

May have found the problem. Will update later. I pulled the Bleed valve assembly out of the T-Piece and found a small nick on the inner edge of the o-ring that seals the Bleed valve. This may also explain why it lets air in but not fluid out, as it's such a small nick in a rubber o-ring.

Keeping fingers crossed for you mate. Sounds like a right nightmare.

 

[JGrant]

Did you manage to resolve this in the end? Got exactly the same problem myself and I think it could be related to the bleed nipple seals