Clutch quiz...starter for 10

Evening all. Just took my 14 year old daughter out for a spin in the GTA...going well until I lost clutch pressure. On limping her home, I can see no obvious Leaks. Once the car had sat for a few minutes I had a little bit of pressure.

Repeated pumping of the pedal shows no obvious leaks.


The slave looks clean and dry. But it’s hard to see clearly even on the Atmo. The visible face of the master cylinder in the car is tired and rusty.

I’m thinking that I should start with the master cylinder, but I just wanted to canvas opinion before leaping in! Any views?

Many thanks,

Phil.

Ok, in the daylight:

-the slave looks dry under the dust cover and
-There is no leak at the master into the
- no obvious leaks in the pipe work

I’ve bled the clutch half a dozen times today and the fluid was dirty but bubble free.

Can select gears with the engine off, but not when it’s

Any suggestions what next please?

Thanks,

Phil

Is the pedal totally floppy or is there any resistance there?

Any fluid in the V of the engine?

Pedal has resistance and no fluid in the v - slave seems to be clean and dry.
I’d probably say the pedal feels almost normal.
No obvious leak at the master either.
Thanks,
Phil

Just to add that pressing the clutch pedal fully is giving about 1cm lateral movement at the slave connection to the fork- I would have expected double that travel.

It may not be directly comparable but the MDR for my A310V6 states that the slave cylinder pushrod movement should be a minimum of 11.5 mm. The GTA MDR may state something similar.

When you say there are no leaks in the pipework, is the pipework on the GTA rigid rather than plastic tube as fitted to the A310V6? The reason I ask is because I've read of a potential problem with the plastic tube in that it can bulge over time and so loose some of the slave cylinder pushrod movement.

I don't have direct experience of this but when I was restoring the A310 I replaced the plastic tube with steel reinforced hydraulic hose as recommended in an article in the Mille Miles magazine.

Earlier in the thread you say you can select gears with the engine off, but not when it's...... Presumably you meant when running. Have you measured the slave cylinder pushrod movement both when the engine is running and not running to see if there is any difference? I think I read somewhere that the plastic tube can be affected by heat. In the A310 the tube is in the same vicinity as the heater hoses so could be affected. If the GTA has a rigid tube or the tube is not near the heater hoses then this wouldn't be applicable.

I seem to recall some comments on here about clutch fork failures. Can't remember the details of the failure but could the clutch release bearing end of the fork not move as far on a failed item such that slave cylinder pushrod movement not really indicating what the other end of the lever is doing? If this was the case I suppose you'd expect the same movement at the release bearing end whether the engine was running or not.

[mettersl]

And to add to this, the Atmo clutch replacement tube supplied by Simon Auto is not stiff enough and will result in too little clutch movement. I have one in my left overs from rebuild box is anyone want to try.
Stephen has a box of the Renault as NOS or you can put in a braided pipe.
Lee

I don't know if its any help, as my car is a turbo. However, I have had several problems relating to the clutch . Mainly the pedal feeling soft. After several attempts at bleeding it by the traditional method, I bought a vacuum bleeder. Instant result. The pedal was much better. After a while though it started to go soft again ( ). It was suggested that high boiling point fluid should be used, due to the proximity of the turbo. I changed the fluid & bled it through. It has been much better since. I bought a set of slave cylinder rubbers from Mecaparts a while ago. Its a pig of a job to do on the turbo, so I'm keeping my fingers crossed.

Update - back from holiday and have fitted a new master and bled the system sufficiently to have a firm pedal. Old master was pretty tired and the fluid in it was dark and dirty. However, unless my bleeding is insufficient (it may be as my pressure bleeder stopped working) the master has not solved the problem.

The lines seem to be in good condition.

A slave in in the post as we speak so I might as well give the system a refresh - its obviously in need of a good flush and fresh cylinders.

The pushrod is mysterious. With the master supplied by Clee, it seems a few mm short, made worse by play in the clutch pedal clevis pin joint. I have parts to make an adjustable pushrod - it might be that the master is not moving full stroke. Has anyone else experienced issues with pushrod length/wear?

Finally, whilst I had the car in the air I replaced the fuel pump with a new one and sprayed anti-corrosion wax all around the steering rack fittings, and inner aspects of the shock towers - generally in good condition fortunately.

Phil

[stephendell]

Genuine masters are hard to find and some of the replacements aren’t quite right. If the bore of yours is unworn and it’s physically the correct length get it blasted plated and rebuilt and that should solve the problem or make an adjustable threaded rod as you suggest.

Clutch line on the turbo is still plastic for about two thirds of the length but not full length like the Atmo. The last third is metal due to risk of melting from the increased heat.

There is a slight difference due to the shaped washer and retaining circlip but I've fitted plenty and it doesn't affect the function if bled fully.

Ask JohnC as he was the one that also noticed a bit of play. This was my finding when asked to check


Piston recess is same at 5.6 mm.
There is a greater land to retaining circlip.The OE circlip is thicker so can't be used. Washer thickness is where the slop is but is max about 1mm. Its all just in the land to the thinner circlip so in theory you could shim it out with a thin washer in piston body or perhaps a thin O-ring slipped on rod.

Clee, thanks. I'm satisfied the piston is moving through its full range now, having crawled in the foot well last night and fiddled around.

I watched the slave moving whilst my daughter pushed the pedal and it is still at or below the minimum travel so:
- I have a slave on the way that I will fit
- vacuum bleeding has given me a firm pedal, but the fluid in the pot was dark and cloudy. I expect the worst of that came from within the slave, but nonetheless I intend to keep drawing through clean fluid.

Failing the new slave and/or bleeding working, I guess the clutch fork could be cracked. Would I still get 1 cm of smooth travel at the slave if it was cracked? I do have some paranoia in this regard as I had a Lotus Excel which had a crack in a weld in the pedal box - a right pain to change - which gave some travel at the slave but otherwise felt ok.

What slave have you ordered? The turbo ones are now almost impossible to find. The inlet port and piston design on the Atmo types are not the same at all.

The car is an Atmo, so I got a TWR one, stamped FTE on it. It all fitted nicely.

However, I am now having fun bleeding it - my Eezibleed doesn’t seem to seal on the reservoir so I have used a vacuum system. Although I had a firm pedal at one point, the travel at the slave was only about 8mm rather that 11mm+ required. If I start the car in gear with the clutch depressed, the car tries to move so it’s clear that the clutch still isn’t releasing enough.

Last go at vacuum bleeding tonight left me with a softer pedal, so I’m not sure if a bubble has moved or somehow I have allowed air in, but I have no leaks anywhere as far as I can see or feel.

I might try again with the Eezibleed tomorrow- perhaps some plumbers ptfe around the reservoir thread will be enough.

My children want to go to a teachers funeral which includes a classic car rally as part of the procession, so I am trying hard to sort it so I can take them in the Alpine rather than an everyday car. I’ve got 10 days!!!! Fine, unless it’s the clutch fork

Have you tried reverse bleeding ?
It's a strategy which has never let me down so far with difficult clutches