Clutch Woes

[Rene Gimenez]

Happy New Year to All!

This is my set up:
Van Diemen RF83 FF1600
Tilton F3 clutch
External slave
AN-3 braided line

This is my problem- after bleeding the line and making sure the it is bubble-free, the clutch goes back to the floor within a minute. When I re-bleed, there is no air in the system. After it goes to the floor it takes me several pumps to get a firm pedal. No leaking or weeping anywhere.

I have done the following:

-Rebuilt the Girling master cylinder
-Change out the Girling for the Wildwood clone
-Replace the slave cylinder

All of the connections are tight. Did I miss something?? Yes, I am at about my wit's end.
Thanks for looking and providing any advice!

Rene Gimenez

[Purple Frog]

#1. Is there a point in the system where the line loops up higher than the slave? If so, you may have an air bubble in that loop that is hard to bleed out.

#2. suspect the master cylinder.

[scorp997]

Check that the pushrod is fully extended. I once had an issue where I ‘thought’ it had the correct clearance, but pushing up on the pushrod moved the piston….

[Rene Gimenez]

The clutch line is routed up from the master into the upper left frame rail and the out of the frame rail slightly down to the slave. Should I remove the slave cylinder from its bracket and hold it at a point where it would be above the clutch line and bleed it that way?

John - Double checked that the pushrod is snug to the piston

[Garey Guzman]

.... Should I remove the slave cylinder from its bracket and hold it at a point where it would be above the clutch line and bleed it that way?...

That's what I had to do when I rebuilt all the hydraulics in my March. I put a 1/4 drive socket in place of the rod, then held it in place when a big C-Clamp and bled.

[bob darcey]

It may help to raise the rear of the car as well.

[DaveW]

It may help to raise the rear of the car as well.

That's what I think will help - you're trying to evacuate air, and it's obviously lighter than brake fluid, so raising the rear helps the air go out the bleeder in the rear.

Also, any type of pressure or vacuum bleeder will help - a continuous flow of fluid is MUCH more likely to flush air out of high air-trapping spots than non-continuous pedal pumping.

If that sort of bleeder is not available, increasing your fluid flow velocity by more rapid & frequent pumping may help. You're trying to keep the flow going so the air doesn't have time to return to the high spot(s) between strokes.

[S Lathrop]

When you rebuilt the cylinders, what type of lubricant did you use on the seals?

Whit the improper lubricant, I have had problems with the air getting into the system as the cylinders retract in use.

[mark elder]

Sounds like a MC issue. Take the line off the MC and block the outlet with a bleed nipple or a bolt with a copper washer (do this with the pedal depressed a little bit; It will save you losing lots of fluid). Bleed if necessary.

See what happens. The pedal should be a rock and stay that way even with a minute of pushing hard on it (and stay that way if you wait 5 minutes and push again)

Report back to the family.

[stonebridge20]

Get one of these. Drill, tap and install it in the very top of the slave pointing straight up and bleed the system from there from now on.

Every FF in my shop including mine has this.

[stonebridge20]

The clutch line is routed up from the master into the upper left frame rail and the out of the frame rail slightly down to the slave. Should I remove the slave cylinder from its bracket and hold it at a point where it would be above the clutch line and bleed it that way?

John - Double checked that the pushrod is snug to the piston

No, you don't need to do this. Your line is routed the same place as mine and every other RF81-83 that came from VanDiemen.
The new "Girling" slaves suck. I've had the same issue as you are having numerous times with new slaves. I automatically do what I described above as soon as I pull one out of the box.

[Rene Gimenez]

Thank you for all of the responses! Now I've got a direction on how to deal with this.

Since it's the easiest thing to do I'll raise the rear of the car first. If that doesn't work I'll isolate the master cylinder by plugging it off and checking for pressure. Either way I'll also order the NPT brake bleeder/speed bleeder assembly from Pegasus.

Will post an update as I make (or not make) progress..

[Rene Gimenez]

Hi Again-

Over the past several days I did the following-
First I capped the AN3 braided line going into the slave cylinder to test the master cylinder. Pedal was very firm, so neither the Master or the AN line seemed to be a problem.
Next I removed the slave cylinder and took apart the plunger shaft assembly. Made sure that the plunger inside the slave cylinder was as far up the slave cylinder as it would go. Reassembled everything and made sure that the plunger shaft was snug with both the slave cylinder and the clutch arm and not fouling the return spring.
Raised the rear of the car and bled (have not received the speed bleeder yet).

The result- I have a very light pedal, and the the clutch arm moves about 1/4 inch consistently. I did check to make sure that there was no play in the clutch arm. This is with a .70 master and a brand new F3 Tilton clutch.

My concerns are these- the clutch pedal is extremely light and is 1/4 enough movement? Many thanks for your input.

[tlracer]

What bore size is your slave cylinder?

[pooch776]

The result- I have a very light pedal, and the the clutch arm moves about 1/4 inch consistently. I did check to make sure that there was no play in the clutch arm. This is with a .70 master and a brand new F3 Tilton clutch.

I always use a 3/4 master for the clutch.

Joe

[stonebridge20]

Hi Again-

Over the past several days I did the following-
First I capped the AN3 braided line going into the slave cylinder to test the master cylinder. Pedal was very firm, so neither the Master or the AN line seemed to be a problem.
Next I removed the slave cylinder and took apart the plunger shaft assembly. Made sure that the plunger inside the slave cylinder was as far up the slave cylinder as it would go. Reassembled everything and made sure that the plunger shaft was snug with both the slave cylinder and the clutch arm and not fouling the return spring.
Raised the rear of the car and bled (have not received the speed bleeder yet).

The result- I have a very light pedal, and the the clutch arm moves about 1/4 inch consistently. I did check to make sure that there was no play in the clutch arm. This is with a .70 master and a brand new F3 Tilton clutch.

My concerns are these- the clutch pedal is extremely light and is 1/4 enough movement? Many thanks for your input.

The new bleeder location will fix your problem.

[Robert J. Alder]

if "No play in the clutch arm" means what it says, the system will be riding the clutch, i.e. riding the throw out bearing and more importantly the crankshaft's thrust washers. All very bad. The clutch arm should have a tiny bit of free play before engaging the bobbin to the pressure plate fingers. Not a lot, but NOT constantly touching. Maybe 1/16+" free-play at the bobbin, which might translate to 1/4" free movement of clutch arm. Burning up a crank's thrust washer because of a too-tight system will not be a happy outcome. Ask me how I know. My issue was a faulty hydraulic slave not retreating and thus "riding" the clutch and burning up a crank thrust washer. But hydraulic or mechanical lack of free play would be the same outcome.

[jrh3]

I had a similar problem with a troublesome car. New Wilwood MCs. Bleed many times and many ways. Would not consistently keep a good pedal. Replaced the defective MC and problems solved.
The valve for fluid fill and return was defective. Thanks Chris Harrison!

Returned the offending new MC to Wilwood who said it was fine but they sent a new MC as a goodwill gesture .
You might consider buying/ borrowing a new or known functional quality MC.

[APEowner]

Make sure that you have a little free play in the master cylinder push rod when the pedal is released. The piston in the master cylinder has to be able to return all the way and if there's no play in the push rod that can't happen.

[stonebridge20]

So.......what was the conclusion to this?

[Roland V. Johnson]

I am pretty sure he is installing an annular unit. I have run across a lot of worn out clutch release cross shafts and bushings and bent levers in the last few years. With the F-3 style clutches they and your clutch leg take a pounding.

[bob darcey]

My first Tilton F3 clutch came with an "orange" diaphragm spring, and it was a bear to disengage. Had it chnged to a "buff" spring and it made a huge difference--the "buff" spring is more than adequate for a 1600 FF.

[Robert J. Alder]

Hi Again-

. . . and made sure that the plunger shaft was snug with both the slave cylinder and the clutch arm . . . ..

Make sure there is a LITTTLE play at the clutch arm. See my previous comment. You do NOT want the bobbin constantly in touch with the fingers.

[Sean Gallagher]

Just buy new Slave & Master Cylinders every year.
This expenditure is a Drop in the Bucket compaired to the time you will waste chasing a problem.

[DaveW]

IMO, unless you have money to burn, that's an unnecessary expense. My master cylinders last for many (>10) years. If they were a "replace every year" item, I'd do it, but I've never had an issue related to master cylinders. I do rebuild the clutch slave every year, and the calipers if the seals get too loose or there's some other issue, but I don't replace them.

Just buy new Slave & Master Cylinders every year.
This expenditure is a Drop in the Bucket compared to the time you will waste chasing a problem.

[LFFR]

...what the inside of a Girling slave cylinder looks like?



The two holes, one is the feed from the master and the other is for the bleed. 3cc of dead airspace up there.

John Mihalich, Jr.
Lotus 61/FF/28

[stonebridge20]

...what the inside of a Girling slave cylinder looks like?



The two holes, one is the feed from the master and the other is for the bleed. 3cc of dead airspace up there.

John Mihalich, Jr.
Lotus 61/FF/28

And that is why a bleeder tapped into the top of a slave cylinder that was originally designed to sit sideways fixes your soft clutch pedal problems.

Ever wonder why there's left and right hand slave cylinders?

To put the bleeder on top depending on which side of a gearbox it's mounted on.

This slave was never designed to be mounted straight up and down. It was originally designed to be mounted sideways.

[Offcamber1]

for enlightening me with the cutaway. I had no idea there was that much dead space in there!

I will be pulling mine off, drilling, tapping, etc.

So really, if you drill and tap the top you can just plug the side opposite the input, right?

Thanks!

[stonebridge20]

So really, if you drill and tap the top you can just plug the side opposite the input, right?

Thanks!

Yes

[Domiteaux]

Yes

Wow, now it makes sense why its always a soft pedal, after 50 years of FF racing with these sleve cylinders suprised no one sell a properly designed version, Hint ( Willwood ) . So machine a basic fitting and adapter with a remote bleeder?

[DanW]

The reason the supply and bleed holes are in that position was due to its original horizontal vs vertical installation position. Remove the slave from it's position, zip tie or hose clamp the piston so it doesn't leave the cylinder under a little pressure, turn it so the bleed screw is at the highest point and bleed again.