Faulty clutch master cylinder?

[Bainbridge]

Hi all

The Mrs reported a "funny clutch pedal" on her 57 plate Astra 1.6 sxi when she got home this evening.

A quick inspection before dark and the clutch pedal has no pressure until 75% depressed, then there's some pressure.

I couldn't engage a gear without a huge grinding noise.

There's no loss of fluid in the brake/clutch reservoir, but I didn't have a chance to inspect for leaks further before darkness fell.

The car has done 117k miles. The clutch started slipping at 100k just over 2 years ago and I replaced the clutch with an LUK kit (friction plate, thrust plate and release cylinder). However, I'm by no means an expert and I had to follow the Haynes manual to do this. The clutch has worked perfectly since it was changed 2 years ago.

I will get out there tomorrow and investigate further, but taking into account the above info, does this point towards a faulty clutch master cylinder?

I can bleed the clutch, I have a pressure bleed kit which I needed to get it bled properly after the new clutch went in 2 years ago.

Of course it could be a faulty slave cylinder, but the new one only went in 2 years and 17k miles ago.

Or am I barking up completely the wrong tree?

Any comments will be most welcome, thanks.

[E-bmw]

Low fluid level or in need of bleeding.

[Gourockian]

This sounds like a master cylinder issue to me.

If there's no loss of fluid in the system but you're still not getting full clutch actuation then it's likely to be failing seals in one of the cylinders. By process of elimination, if you've already swapped the slave, then it's probably the master

[Bainbridge]

Thanks for your responses.

I do hope it's the master cylinder and not the slave, changing the clutch was a real achievement for me but I don't really want to have to get the gearbox off again, and all that this entails

[TwinKam]

Check that the pedal is returning fully (lift it with your toe), Vauxhalls of that era are prone to breaking their return spring meaning that the master cylinder doesn't get to refill. Unlike the Corsa, it is (just) possible to replace the spring without taking the pedal box out, but it's not a pleasant job, from memory you need to take the column out to get the access. In the short term you can still drive it as long as you remember to lift the pedal every so often.

[Bainbridge]

It did indeed turn out to be the clutch master cylinder.

@TwinKam I did check the spring and it was in position.

It was £125 for the replacement part, a simple but very awkward job to fit, and the gears engage fine again.

Thanks again for your input, everyone.

[Bainbridge]

Update: she now has a spongy pedal. I must have not fully bled the system.

Rather than pulling out the battery and tray to get at the bleed valve, I managed to slip my hand in a tight gap with a ratchet spanner and loosen it until I had a spurt of fluid.

Looks like I'll have to take some bits off to get a pipe over the bleed valve above a receptacle and bleed a good amount through.

That'll teach me not to be lazy.

[Bainbridge]

Update

It seems to have fixed itself.

I was planning on pulling out the battery and tray this weekend to flush a reservoir of fluid through the clutch line, however the Mrs reports than the pedal has gone back to normal and is fine.

I'm thinking that gravity might have done its job over the past week and any air bubbles thankfully worked their way up.