Clutch pedal free play

I have just replaced the clutch slave cylinder on my 1970 Series 2 FHC since it was weeping. I have only had the car for 3 months and have never took much notice of how far the clutch pedal travels before it start to move the master cylinder piston and hence the slave cylinder piston. But having replaced the slave and bled the clutch I notice that about 1/4 of the pedal travel is free play which surely is too much. The ROM says that the push rod that connects the pedal to the master cylinder is not adjustable so there is no way to remove , say, half of this free play. I had the same problem on my Triumph Spitfire when I restored it but in the Spit’s case there was so much free play the clutch would not release cleanly which is not the case with the E type which releases fine. On the Spit I extended the push rod and I’m thinking of doing the same on the E type. My thinking is that the master cylinder has been replaced at sometime and the push rod supplied is simple too short. Any comments?

Hi,

1/4 of the clutch pedal travel?

1/4” would be ok (6+mm) at the slave, IIRC 1/16-1/8” (?) if you can adjust the rod.

The most important part of course is that there IS SOME free play so the release bearing (TOB, made of graphite) is not touching the pressure plate as it would quickly wear out and is an engine out job to replace.

Also good that it fully releases, easy to notice when engaging gears.

Cheers!

Can you provide a picture or part number for the new slave cylinder you used?

The free play you describe seems excessive (mine move about ¼" at the bottom of the pedal before it moves the master) though for me the more important metric is where in pedal travel does the clutch release.

You certainly want to exhaust other issues before going with a special longer pushrod as I do not think that should be necessary if all else is right.

Does the free play (briefly) become less if you pump the pedal several times? If yes, that would suggest the line is not fully bled of air.

A photo of the installed slave may also be useful.

Further to Geo’s comment about exploring what you have a bit more: have you checked if the hole in the clevis at the end of the push rod has become oval and sloppy on the pin? This happens over time, and results in a lot of slop in the pedal. The length of the pedal amplifies a small amount of slop considerably. If this is the case, you may have to have the hole welded up, and then re-drilled.

1 Like

Yes Mr Langley I think that you are correct

I can assure you that there is nothing amiss with the slave cylinder or that there is air still in the system. It is quite apparent that the play is at the pedal. Pressing the clutch pedal by hand you can immediately feel the resistance when the push rod starts to move the master cylinder piston. David Langley’s suggestion that the clevis and/or clevis pin is worn is a possible reason. I will have to investigate but as you know lying on ones back under the driver’s side is pretty difficult. I will probably have to take the driver’s seat out to do this.
Stuart

I would reach under and take pictures before taking the seat out.

Just wondering if you installed a hydrostatic slave and have adjusted it tio that standard.

Well I was wrong! The clutch is not clearing enough to get the car into reverse gear and it barely clears enough to get into the forward gears. Although I thought that I had got all the air out since I bled a lot of fluid through the system I guess there must be still some air in and bleeding isn’t helped by the fact that the bleed nipple is on the bottom of the slave cylinder . I can feel that there is some free play between the clevis on the master cylinder operating rod and the clutch pedal but I would not call this excessive at all , it may be 1/4 ins at the most. So the question is since the pedal goes down about one quarter of its’ full travel before the slave cylinder starts to move is it just air in the system or something else.
I would like to thank all the guys who have given input on this issue. As I am a newbie to E types I am sure that I will be bothering you guys with other questions

Yes, if your slave is weeping you need to fix it. Also check your sills for brake fluid staining the paint. On mine it didn’t lift the paint but I noticed grey spots all down the sill. Apparently it takes the colour from the black hoses and it showed grey on my yellow car. They are hard to bleed so just keep at it.

The new slave cylinder I installed was part number C29801 and was identical to the one I removed which was leaking. This is the none hydrostatic version with the external spring that ensures the slave piston is fully retracted. I did notice that when trying to set the 1/16 ins free play in the cutch actuating arm that this required the slave push rod to be screwed so far out that in barely screwed into the clevis so I screwed it in a bit further and hence there is a little more than 1/16i ins free play
I will have a go at bleeding the clutch more but just at the moment I am so annoyed that replacing the leaking slave with a new one has given me this clutch clearance which wasn’t evident with the leaking one so have left the E type sulking in the garage and taken a break.
If I can’t get anymore air out I don’t know what I will do. Does any one have a better method of bleeding than the normal method of opening the bleed nipple on the down stroke of the pedal and then closing it while holding the pedal down before letting the pedal back up?

I routinely use a simple pressure bleeder on the brakes. I have never had the need to use it on the clutch but no reason why it wouldn’t work and might possibly help.

I make it from a bicycle inner tube - this one (though other sizes will surely work, especially as the top of the clutch reservoir is smaller than the brakes):

I cut it well away from the valve, fold one end closed and secured with clamps, the other end zip-tied to the top of the reservoir:

Only modest pressure should be used - say, 12 psi or so.

If you want to make easy to open and refill the reservoir during the process… @Michael_Frank discovered that the cap from a plastic Coke bottle is a perfect fit. I tried one (I am the sort who touches something labelled ‘wet paint’) and he is quite right. You could zip-tie the end of the inner tube to the cap (drill a hole in it) instead of the neck of the reservoir.

Stewart trying to diagnose this from long distance is difficult. So things I say may be repetitive so forgive me please.

Bleeding - the tip off for air in the system is whether pumping the pedal temporarily relieves the symptoms. you haven’t said anything about that. Bleeding the clutch slave is difficult as you have noticed due to the reversed placement of the inlet and outlet. Many of use have fabricated new lines so the fluid enters the bottom and the air out the top, but that’s excessive. There are quite a few threads on this site were people talk about methods they use, it might be a benefit for you to look at those if air is the problem.

Free play in the pedal. The m/c set up is that the m/c entirely controls the position of the pedal. It can only be adjusted by changing the thickness of the spacer to move the m/c closer or farther from the pedal. It does this by a spring in the m/c., and by having a washer circliped into the mouth of the cylinder that stops the pushrod from moving further back (coming out of the m/c bore). Hence I’m not sure what you mean by free play there. The clevis on the pushrod wears remarkably quickly and badly. As the system is designed to have the pedal bottom out either at the carpet at the footwall closing panel or very close to it, wear in the clevis becomes a problem if it is excessive enough to cause the pedal to bottom on the carpet etc before full stroke is realized. Usually this is not an issue as the system provides more than enough stroke to fully open the clutch with out bottoming in the m/c.
A side issue here is the spring in the clutch pedal assembly. Typically these were such low quality/poorly engineered devices they break or collapse quickly and the pedal sits in effect on the push rod only. In the unlikely event the spring is still functioning properly that would pull the pushrod back to the extent of the wear in the clevis and show true free play. Bear in mind that given the mechanical advantage built into the pedal the pad moves back significantly more than the amount of wear in the clevis. You can determine the amount of wear in the clevis simply by pulling the pedal backward and forward. It will always have a small amount (1/8 inch?) but it may not really matter.

By free play do you mean that if you were to watch the slave it would not start to move until the pedal is a 1/4 down, and the m/c pushrod is fully engaged at the start of the stroke? That is unlikely but it could be air in the system, or something wrong with either of the cylinders.

To fully operate the clutch the slave only has to move the slave pushrod clevis rearward by between 5/8 and 3/4 of an inch (.64" to be precise), not including the recommended free play (1/16") in the TOB. Are you getting that movement?

Just some thoughts.

1 Like

To inspect the movement of your slave cylinder, set your camera on video and slide it under the car, then press the pedal. You can retrieve the camera and review the movie, which may help you understand what’s happening.

My guess is that you have air in the system. I’ve never used pressure or vacuum to bleed brake or clutch lines, nor do I think it’s a good idea. Just use foot pressure. The fact that the bleeder is at the bottom isn’t especially relevant, either. Find a small diameter hose and place one end over the nipple, the other end gets dunked into a jar with some brake fluid in the bottom. Pump out about half a bottle of fluid, then tighten the bleeder. Simple one man job,

Since ofttimes I worked alone, I used that method a lot. Works well.

Just a thought, are you sure the piston in the master cylinder is not hung up partway through its normal travel?

Several years ago when I replaced my slave I initially could not get it to bleed using a vacuum bleeder or by pumping the pedal. I then let it sit for a few hours with the bleeder left slightly open so that it could gravity bleed. I checked the level in the clutch bottle and jar underneath occasionally during the gravity bleed. After a few hours I got some pedal pressure so I finished off the bleeding process with a few more pumps using my one-man bleeder like this. I still like it best of all the bleeders I have tried but I have not done the bicycle tube method yet. It might work better for the E-type configuration.

https://www.amazon.com/OEMTOOLS-25036-Bleed-One-Man-Bleeder/dp/B000CMDP44

David
68 E-type FHC

Slacken the feed pipe connection and pump, air may come out there.

I found my problem. It was my own stupidity. The slave cylinder acts like a hydrostatic one it that moves out until there is no slack between the pushrod and the clutch actuating lever. The external spring strength must not be set so strong that it pushes the slave cylinder piston too far back. This was my mistake. After I had set the clearance on the actuating lever I just stretched the spring really tight thinking that was what was needed. This resulted in the slave piston being pushed too far back. So when I pressed the clutch pedal all the extra clearance had to be taken up before the clutch actuating lever disengaged the clutch. Now If I try to select reverse with the clutch disengaged without waiting for the gearbox to stop turning I do get a little grating of the reverse gear so I first select first gear which stops the gearbox and then select reverse. You can see in the photo that the spring is only slightly extended so it doesn’t push the piston back. I don’t understand how the hydrostatic slave works. On my Triumphs the slave piston moves so that there is no clearance between slave cylinder rod and the clutch actuating lever hence taking up any clutch wear. The clutch release bearing is not pressing so hard against the clutch diaphragm spring that it rotates continuously
Thanks to all who offered advice

Stuart