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Quattroz
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PostPosted: Wed Sep 18, 2013 9:59 pm Reply with quote Back to top

Greetings AudiFans

Went to take my '87 CQ for a spin and the clutch pedal went strait to the floor and stayed there.
Checked reservoir - Cracked and empty.
Replaced reservoir and pumped (bled) a whole bottle of new fluid through the system (having to pull the pedal up each time) but still no clutch activation, it is like the pedal is permanently depressed, no drive getting to the gearbox at all.
I am getting good pressure in the system when the bleed screw is tightened.

Does anyone know which part of the system is at fault?
Is it the master cylinder?
Is it the slave cylinder?
Is it the clutch its self?
Or is there (ever hopeful) just something that needs reset somewhere?

I've been reading other posts and don't want to go replacing the master cylinder if it isn't at fault etc.

Thanks
John
New here but on my 6th Audi of one shape or another.
 
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Mikes2
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PostPosted: Thu Sep 19, 2013 4:56 pm Reply with quote Back to top

Is the fluid still disappearing or is the reservoir now full and staying that way

Strong possibility of a master or slave fault.

Think there's also a return spring on the pedal that can fail.

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Quattroz
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Joined: Sep 18, 2013
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Location: Edinburgh-ish

PostPosted: Thu Sep 19, 2013 9:58 pm Reply with quote Back to top

Thanks for the reply.

New reservoir still full after over 24 hours and there is still pressure in the system.

With the bleed screw loose, the pedal can be pressed to the floor and stays there. However there is an over-centre return spring on the pedal that brings the pedal back up if it is lifted a bit.

When the bleed screw is tight the pedal can be pressed a bit and feels not unlike a brake pedal if you know what I mean.

After some more thought, I am starting to suspect the slave cylinder or even the clutch its self.

The master cylinder seems to be generating the pressure OK, I can feel the hose from the bulkhead to the slave cylinder flex with the pressure when the pedal is pressed.

Is it not unusual for a clutch to fail suddenly in a disengaged state and while not in use. I find it odd that it is stuck disengaged considering how strong the springs are that usually hold it in an engaged state until the pedal is pressed.

Can the slave cylinder jam?
 
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Mikes2
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PostPosted: Fri Sep 20, 2013 2:37 pm Reply with quote Back to top

The slave usually falls apart.

Not sure if yours is the early type with a roll pin or the later bolt version.

It's probably the roll pin type. you'll need a punch to remove the roll pin. The slave can then be removed with the hydraulic line still attached.

The hydraulic line can also cause problems. You should undo it and confirm fluid is getting all the way through.

My recommendation would be to remove the slave and check it's all there. If it has fallen apart, you'll probably need to remove the gearbox to sort.

What's the miles on the car ?

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Quattroz
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Location: Edinburgh-ish

PostPosted: Fri Sep 20, 2013 2:54 pm Reply with quote Back to top

The car has done 168,000 miles.

It is the older roll pin type with the clip.

I think the line is OK as it is holding pressure and was bleeding OK too.

So if the slave cylinder has failed, it is theoretically possible that it is not returning and therefor the clutch is being held disengaged.

Strange that the slave cylinder should fail in such an odd way and at the same time as the reservoir.

Looks like the slave cylinder will have to come out. Don't know when I'll find the time.

Thanks for the help.
 
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Quattroz
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PostPosted: Fri Sep 20, 2013 3:07 pm Reply with quote Back to top

Oh! forgot to ask. Can the roll pin be pushed out in either direction?
 
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Mikes2
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PostPosted: Fri Sep 20, 2013 9:49 pm Reply with quote Back to top

Fail safe if it fails like that. When you push the pedal, the master cylinder pushes fluid down the line to the slave.

The pressure then pushes the pushrod of the slave to operate the clutch.

It's quite common for the pushrod of the slave to break.

Access to the roll pin is tricky. think it's normal to push it through from the passenger side wheelarch

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Quattroz
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PostPosted: Sat Sep 21, 2013 12:29 pm Reply with quote Back to top

I found some time this morning and pushed the roll pin out with a 5mm punch by leaning into the engine bay. There is enough room to swing a heavy hammer behind the radiator. The difficult bit is seeing what you are doing. With the steering at full lock to the left I could just see.

Getting the slave cylinder out is the tricky bit. With a large punch held in a 14mm socket and some extension bars I could just get to the shoulder of the slave cylinder where the hydraulic line attaches. I was a bit worried about belting this to hard as the angle was a bit steep but after a while it started to shift.
When I removed the cylinder there was no push-rod to be seen and the rubber seal was perished and the fluid was more like thick grainy mud.
Next thing I heard was a clunk and a rattle. I am assuming this was the clutch main spring pushing the push-rod back somewhere and the push-rod then falling down inside the bell housing.

I presume that my only course of action now is to separate the gearbox/bell housing from the engine.

Can anyone confirm?
Are there any tricks?
 
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Mikes2
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PostPosted: Sat Sep 21, 2013 11:48 pm Reply with quote Back to top

Not so good. Sounds like the pushrod has fallen down inside the bellhousing. If you're lucky, you may be able remove the lower inspection bracket and find it there.

other possibility is to remove the starter motor and see if it can bee seen from that side.

Otherwise it's gearbox off time

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