VW trike hydraulic clutch problems

[Zar]

hello Trike Talk people... first of all, thank you for letting me join this forum, I hope I will be able to be of help from time to time.

~ I am currently building a VW powered monster of a trike, and I'm in the semifinals, but the conversion to a hydraulic clutch system is where i hit the wall. I will try to describe what is going on to the best of my ability. I have a C&C slave cylinder properly installed, a 3/4"master cylinder as it is recommended, my flywheel, pressure plate and clutch pad are the correct type for my type 1 VW transmission and are new and in perfect and working condition, all the torque values are correct... I bled the system 3 times, and made sure there was no air in the system and at first everything looked to be working fine... but ones I got the engine fired up, the clutch would not disengage...

after a very complete Inspection, I found that the slave cylinder would only actuate up to the place where the throw bearing engages the pressure plate fingers, and stop. no mater the adjustments on the slave cylinder, it would only go that far... I took all the slack out of the slave cyl. push rods and the pedal was unmovable. I can disengage the clutch i by using a pry bar on the tranny throw arm... I also had the company that sold me the slave cylinder, send me a new one... but it made no difference.

Thanks,Cesar.

,

 

[Gorilla]

Cesar welcome aboard our VW people should pickup on this shortly.

 

[LarryA]

welcome to trike talk..1st thing I thought, does your mc have less fluid capacity than the slave needs? failure to disengage because of insufficient slave travel. Next thought....is there a problem with your throw out bearing length or fork geometry.

When you say you can disengage the clutch with a bar, can you actually shift into gear with out grinding gears? when you removed all lost motion with slave adjustments....it led me to believe there are problems within the bell housing......

no vw expert ,but have converted cable chrysler to hydraulic If recall 3/4 mc 7/8 pull type slave.

There are highly experienced vw folks on this site that will chime in with better advice than I

 

[DeathBySnuSnu]

Ok. At full extension it should be at the same point as an adjusted cable.

As in at full extension the throw out bearing should just be retracted away from pressure plate. I dont have actual numbers but somewhere around a quarter inch of slack before the throw out makes contact.

It sound like air to me though. Either not all out or something is re-introducing air back in.

Or possibly the cup in the master is bad.

 

[Zar]

welcome to trike talk..1st thing I thought, does your mc have less fluid capacity than the slave needs? failure to disengage because of insufficient slave travel. Next thought....is there a problem with your throw out bearing length or fork geometry.

When you say you can disengage the clutch with a bar, can you actually shift into gear with out grinding gears? when you removed all lost motion with slave adjustments....it led me to believe there are problems within the bell housing......

no vw expert ,but have converted cable chrysler to hydraulic If recall 3/4 mc 7/8 pull type slave.

There are highly experienced vw folks on this site that will chime in with better advice than I

I can desingage the clutch with a pry bar, and don’t have to even push it all the way, and I can get in to gear with out grinding -

 

[Zar]

I bled the system 3 times, and found no air at all the last time, after pressing the pedal and adjusting the slave several times... I also checked for leaks and found none... how can I check for a bad master cup?

 

[DeathBySnuSnu]

At first it seemed to work?

As in it did draw in the lever.

But then later it did not release the clutch and when you inspected it, it was not drawing in the lever.

You operated the lever with a bar and know it moves as it should.

So now you push the pedal down it takes out the slack but does not pull the lever even though the pedal continues to travel down.

The pedal moves and the slave does not?

As you changed the slave and the fact that it would be leaking fluid out, I doubt that is the problem.

The number 1 cause is air. If that is eliminated that leaves the master.

Did the piston stick, did the cup seal fail?

Way back when I first built mine......I had gotten the brake master and worked on linkages.....worked it in and out a lot......left that part the sit and moved to other things......by the time the final assembly and bleed came around the master was bad and would not displace the fluid.

 

[LarryA]

Something I added was, a residual pressure valve between master and slave....the slave is mounted about 12/16 in. above the master.....I was worried about drainback into the master. I think about a 10#....maybe the one for drum brakes from "speedway".

now...... the chrysler transverse setups did run with the throw out turning continuousley against the pressure plate like some semi trucks do.

In your situation, with a throw out that sets back with clearance from the p-plate this may not be a good idea???

If your problems are indeed caused by drain back...I would watch for increasing fluid levels in the mc.

One last thought...your mc, ( If pedal linkages are set correctly) should give a little burp in the mc fluid when you just begin to press the brake pedal....this signifies that the cup has returned enough to reload the cylinder for the next stroke.

this is something that can be easily overlooked when working with linkages.

 

[DeathBySnuSnu]

Larry has a very valid point.

I did just assumed you have your linkage and lever all sorted.

So do you?

Lever lengths?

Travel?

Full retract/ push rod slack?

 

[Zar]

The pedal stops where the Slave stops. and I changed the slave cyl, because I thought it was bad.. but it wasn't leaking.

-I don't see any fluid leaks by the M.C. or anywhere in the system. I also don't see a significant l change on the level of fluid on the M.C.

so maybe I need more fluid capacity on my M.C. but the thing that throws me off, is that when the Slave is not engage to the tranny, it has more than enough travel to operate the clutch, but when it's attached to the throw arm, it does not have the power to push past the fingers.

- so, based on all the things you guys are suggesting, it is most likely the wrong M.C. or a bad M.C .

-if my M.C. is d=bad, how can I test it. ?

and if I need to change it, what M.C. do you guys recommend to go wit this CNC slave.

this is my first build, and when I got the M.C. for the clutch and brake, I made sure it was 3/4", and had a big cup. this is what I have in it.

 

[Zar]

Larry has a very valid point.

I did just assumed you have your linkage and lever all sorted.

So do you?

Travel?

Full retract/ push rod slack?

Lever lengths?

Full retract/ push rod slack?[/QUOTE]

My pedals ( I built ) presses the M.C. all the way in, and lets it go back all the way... and I think are straight .

 

[DeathBySnuSnu]

Nothing wrong with that brand or style of master.

Still by everything you say it still sounds like air. Things can be hard to bleed sometimes, especially if you are by yourself.

So what I said about the master..... when first time building mine I worked the pedal so much and the master was too dry. I wore out the seal cup. It would not seal up and make pressure.

Took the master apart and went to the local auto parts store and bought a 15 cent seal cup. Put it in and away I went.

 

[Zar]

Thanks- so if the M.C. was bad... I would see leaking.. Right ?

-I bled the system with the help of my fried Troy, who is an experienced mechanic ( not to familiar with VWs ) and we used a vacuum type bleeder, and also did it the old school way, I also removed the slave cyl, from the tranny, and moved it around as we bled it.

Question: so if there is air in there still, the pedal would be soft. ?

But the pedal is firm all the way until it stops-

- I'm going to try to bleed it again, and check for any leaking in the system.

 

[DeathBySnuSnu]

Describe that some more.

You push the pedal.

The slack tightens up on the throw out.

The slave stops moving.

The pedal continues to move.

Continues to move with some tension but no more movement from throw out.

 

[Zar]

Describe that some more.

You push the pedal.

The slack tightens up on the throw out.

The slave stops moving.

The pedal continues to move.

Continues to move with some tension but no more movement from throw out.

I push the pedal.

the slave cyl puls the throw arm until it touches the P.P fingers.

the pedal also stops moving.

if i adjust the slave, and take it all the way, till it hits the finger , the pedal and slave won't move.

no mater how i adjust the slave... it will always go to the same point( the fingers)

the first pic is before pressing the pedal... if you can see the markings by the base of the throw arm .. the last dot is where it need to go, the dot before that, is where it touches the fingers ( all the slack out )

 

[LarryA]

your mc looks to be exactly the one I am using....with 3/4 mc and 7/8 pull slave I have enough travel, but very little extra, not good to overtravel a pressure plate anyhow.

when you reach that point of contact , does the brake stop pedal rock hard, or does it slowly go to the floor?

I'm wondering if the mc is bypassing on the cup, or if the mc is jammed up inside ,or missassaembled?

I would take that mc apart and look....could even be wrong pushrod or piston length....then I would call willwood and ask them what parts and dimentions the parts should be. I'm sure they will be glad to help.....they have a reputation to protect.

 

[DeathBySnuSnu]

Ok.

We may be getting somewhere now.

This is a whole different set of symptoms than first understood.

Press the pedal.

Pedal and slave move until contact/slack taken up.

Slave stops.

Pedal stops also.

Pedal is solid and unmoving.

Does NOT continue to move.

Also from before. Clutch works with pry bar. Slave and master travels full stroke when not connected to throw out.

Is this now the correct symtoms?

If so then the mechanical ratio of your foot pedal is to low. Should be around 7 to 1.

If it is ......say 2 to 1....it will take a whole lotta pressure on the pedal to work.

If this is the correct list of symptoms then try pressing harder.

 

[Zar]

those are the correct symptoms... but pressing harder does nothing (did try )- I'm about to go to the garage and try to bleed

it again... I just saw a video that might help me get air out, if there is any:

if not, I'll have to take the MC out and do a good inspection. and also make sure that my pedal is doing the job it is suppose

to do,,, as I said, I built it myself out of old timing gears,,,looks awesome, but looks aren't everything.



Thank you guys for all the help. I will update after I do the bleeding.

Just can't wait to ride this monster!

 

[DeathBySnuSnu]

Let's work the numbers and see what we get.

1) which pressure plate do you have?

2) length of lever, hinge point to clevis?

3) length of lever, hinges point to foot pad?

4) we already have mc bore.

5) we already have slave bore.

6) and we have the stock throw out fork.



Stock beetle.

600lb plate

Stock throw out

Cable

7 to 1 pedal.

Equals 42 lbs of push on the pedal. Which is nothing for a leg to push.

So now let's guess yours out.

Super heavy duty "bus" pressure plate.

Stock throw out.

.857 ratio on hydraulic (.750/.875)

Foot side of pedal 6 inches.

Master cyl side of pedal 3 inches.

Equals 257 pounds of push on the pedal.

 

[LarryA]

pedal ratio could very well be the problem, considering the seemingly normal hydraulic function.

use a temporary lever on the clutch pedal to get 7/1 and give it a try.

also, I would watch the strut for the slave that is standing out from the case, see if it deflects under load, if so it could contribute to lost motion.