Clutch problem

[how_lotus]

Hi everyone,

Just bled the clutch on my 72 S130, feels good at the pedal with almost no free travel. That is until i re-attach the return spring. Then the pedal is horrible and sloppy. Have bled several times and checked no air in the system. The master, slave and braided hose are all new.

What is going on? As soon as I take the spring off again the pedal feels normal?

Any ideas,
Howard

[JonB]

Return spring? That'd be the one on the slave cylinder, right?

Does the clutch actually work without the spring?

[how_lotus]

Yes thats the one, it works fine without the spring, however if I put the spring back on its horrible. I've never come across this before.

[oldelanman]

The master, slave and braided hose are all new.

A couple of thoughts...
Did you check/adjust the slave cylinder pushrod clearance and does your replacement master cylinder have the correct length pushrod, I believe you may need to reuse the original.

[how_lotus]

Yes I have checked clearance and have used the original pushrod. I'm worried now I may have made a mistake assembling the clutch, despite having done this many times before without any issues.

thanks

[1969Elan]

Hi , I had a similar problem with clutch engagement and travel at slave cylinder after an overhaul of my
Clutch and hydraulics.
Some master cylinders have a long rod with a spacer fitted at the pedal box, and others have a short rod with no spacer.
A previous owner had fitted my car with the short rod and the spacer at the pedal box which restricted travel at the slave cylinder and the clutch would not engage.
I removed the spacer at the pedal box which increased the travel and all was fine.
It’s worth checking as it puzzled me for quite some time and I also thought
I had fitted the clutch incorrectly .

[69S4]

It's not the slave cylinder moving in the mount is it - the spring pulling it back so there's some 'slop' to take up before it hits the circlip?

[how_lotus]

Thanks for all your comments and suggestions, I decided to take apart the new master and new slave to compare parts with the old units and found that the piston in the new slave cylinder is around 5mm shorter than in the old unit which probably makes a big difference. Not sure whether I was sold the wrong slave or the old piston is not available? Anyhow I have swapped the pistons over and will refit soon. Hopefully all will be well.

Thanks again
Howard

[alan.barker]

If the Slave moves backwards and forwards in it's location in the Bellhousing you need to stop that.
Some people fit 2 Circlips or a Jubilee Clip round the outside to stop sliding movement
Alan
ps if the Piston is shorter in the Slave surely you will adjust that out when you set the clearance

[how_lotus]

Thanks Alan, yes I will fit another circlip.

Howard

[JJ66]

If your slave piston was too short then pumping the pedal (without the retune spring) will get a nice position but the slave piston may be sat away from the back wall of the slave housing. Then when you fit the return spring, the spring will apply pressure to the slave piston and the fluid will push back up through the master cylinder (as you will know the centre valve in the master cylinder is open with pedal in rest condition) and the slave piston will now have a chunk of clearance between it and the push rod, leading to a weird pedal until you pump fluid through the system again. Hopefully the longer piston (or a long slave pushrod) will do the trick. Let us know how you get on. Regards, Jonathan

[how_lotus]

Yes thanks Jonathan, I finally got round to bleeding the clutch again today and with the shorter piston I now have an excellent clutch. Albeit with a little more freeplay than I would like (about 1 inch), once I had adjusted to the 2mm clearance. I guess you can alter this with an adjustable pushrod in the master?

Howard

[JJ66]

Hi Howard, yes, an adjustable push rod in the master cylinder is useful but be sure to always leave a little free play so that the centre valve remains open at rest. There may be wear in the pedal box pivots that is contributing to this as well. Hope all goes well. Jonathan