Was hoping someone might be able to tell me if it's more likely to be master cylinder or clutch and slave cylinder that's the issue. Or a way I can find out. 

 

Pedal was sticking down but car still drove. Was sticking down at biting point. Bringing it back up manually by foot and pumping a few times helped a little. A week later and now won't go into gear and pumping the clutch doesn't help. Car is MK3 2.0 TDI with 105,000 on the clock. 

 

What's it most likely to be? 

 

Really appreciate the help. 

Hows the fluid level?  Id check that first up.  shared with the brake fluid as far as I know.

 

I'd look for evidence of fluid leakage on the firewall or inside above the pedals.

 

If there its the master cylinder and maybe easier to repair than the slave which may be inside the transmission bellhousing. 

 

If there is fluid leak under the trans it's the slave.

 

Maybe a leaking pipe union.

Mine failed on a MK2. Master cylinder leaked and pedal would randomly stick down as yours does. Lift it up and it would be fine for a while. Clutch eventually failed due to low fluid. The fluid was collecting on the undertray so didn't notice until it got winched onto recovery truck. If replacing master theres a small rubber grommet on the MK2 that is difficult to notice and usually sticks in the old one. You need it for the master to seal properly.

Alasdair

The problem will be the concentric slave cylinder drawing in air through the O ring joint on the feedpipe within the bellhousing.

 

Remedy is gearbox out, replace slave cylinder and usually clutch and DMF while its apart.

6 hours ago, BlueWagon said:

If there is fluid leak under the trans it's the slave.

 

That will be the failed component but there will be no fluid leak, just air drawn in, bleeding the clutch brings temporary respite.

So have looked for leaks etc but can't see any but my brake fluid reservoir is below min it seems. Brakes have been working fine.  Shouldn't there be a warning on dash when it goes this low? 

So with this info would you say master cylinder or slave?

 

Thanks again and for the replies so far. 

AFAIK, brake fluid level that low should be flagging a warning on the instrument cluster. Can you see a sensor on the reservoir?

Might be worth checking brake lines/calipers/flexi etc and the brake master. if its that low I am surprised light didn't come on as well. I would assume the level for the clutch is slightly higher than the brakes( it is on my MK2)  but reckon it wouldn't go that low if its just the clutch leaking. You may have pulled air into clutch line?  You could also be losing fluid through braking. Had leak in rear flexi but brakes worked fine till light came on

Alasdair

Edited 18 February, 20251 yr by Alasdair1

Scary to see such negligent basic vehicle checks, OK I know that the low level warning light should come on but that is a serious leak from the braking system which would normally be sensed by the pedal feel.

 

If it were not for the clutch sharing the same bathwater there would soon have been total brake failure, I suppose that in itself is a safety measure.

 

Reservoir looks nothing like those on earlier vehicles and it looks very close to what appears to be a heat source, GPF perhaps?

 

Can someone confirm that it is indeed the brake & clutch fluid reservoir?

2 hours ago, Tcuk31 said:

Shouldn't there be a warning on dash when it goes this low? 

 

I think you'll find there is a low fluid warning on the brake system but the fluid level is probably not quite low enough to trigger warning on the brakes yet.  Low on the reservoir is not empty, just the minimum level where everything can work fine.

 

You said it was a week ago the clutch was playing up so it's a slow leak.

 

I'd top it up and bleed the clutch system then start looking for leaks.

 

Get someone to pump the pedals slowly and look for leaks underneath and in engine bay on firewall.

 

As suggested by someone it could also be in the brake system.  You just noticed the clutch failing first as it draws fluid from higher up.

 

 

Thank you. I think I'm just going to have to get it to a garage for investigation instead of trying to diagnose myself. Just assumed it would be the clutch as the symptoms of pedal sticking down etc are what others had, but if  it's a leak on the braking system then I'd rather that got diagnosed. 

 

Thanks everyone. 

38 minutes ago, BlueWagon said:

I think you'll find there is a low fluid warning on the brake system but the fluid level is probably not quite low enough to trigger warning on the brakes yet. 

 

Assuming that is the brake/clutch fluid reservoir, the level sensor is usually built into the cap and if working will create a low fluid warning when the fluid level is significantly higher than the outlet for the clutch master cylinder.

 

"Low on the reservoir is not empty, just the minimum level where everything can work fine."

 

The "minimum" mark on that reservoir is right at the bottom, that is lower than low!

 

Are we sure that really is the brake/clutch fluid reservoir?

 

 

Edited 18 February, 20251 yr by J.R.

10 minutes ago, J.R. said:

 

Assuming that is the brake/clutch fluid reservoir, the level sensor is usually built into the cap and if working will create a low fluid warning when the fluid level is significantly higher than the outlet for the clutch master cylinder.

 

"Low on the reservoir is not empty, just the minimum level where everything can work fine."

 

The "minimum" mark on that reservoir is right at the bottom, that is lower than low!

 

Are we sure that really is the brake/clutch fluid reservoir?

 

 

It's definitely the reservoir. Has dot 4 written in the cap. 

I reckon the sensor in the reservoir has stuck or failed or bad wiring/shorted out. Try removing it completely and see if the light comes on when hanging lose out of the reservoir. Mine on my MK2 puts light on plus alarm when about 1/4 full. A garage should be able to track down a leak easier as they can lift car for proper inspection. Remember to top up with fluid before driving anywhere. If the clutch isn't working you could try bleeding it to see if it will come back to get you to garage. At least you can read your reservoir. Mine are so opaque you can't see the level easily.

Alasdair

It could be a LED failure, not uncommon.

Had a quick look and it looks like the reservoir on a MK3 has a sensor not a float switch. The ones I have seen online don't seem to have wires from the cap. If the sensor has failed it would explain why no warning lights.

Alasdair

So I have put some fluid in. Pumped the clutch about 10 times and it held so managed to get it in gear. After a few times of putting it in gear I have to pump it again. I think maybe it needs bleeding. May be a possible leak straight down from where I filled it up but this could also be spillage so will look again tomorrow. Fluid level seems to be holding so far. 

Give it a blast of brake cleaner and let dry then leave for a while. It may be leaking as it leaves the reservoir to clutch. I've had a few leak there.

 

You will 100% have to bleed it.

 

Its a very easy process, gravity is your friend, push a short lenght of clear tube on the vertical bleed nipple on the bleed block AKA peak torque limiter, open the thumbscrew and watch the bubbles rise, close as soon as it runs clear, takes less than 10 seconds.

 

Others will tell you that it has to be pressure bled, I speak from experience.

Bled it earlier and it's made no difference unfortunately.