bleeding clutch line

[dmiller]

when the clutch slave cyl is not pressing against anything, it moves almost an inch when the foot pedal is depressed.

when the clutch slave cyl is connected to the clutch release arm, it move only about 5/8 of an inch.

this makes me believe that i must still have air in the line, but when i bleed, i see only fluid with no bubbles in the bleed line. does this mean that there are air bubbles in the line, and i must bleed more to sweep them down?

thank you.

doug

[GeorgiaSnake]

Doug I think you are just seeing the effects of the pressure needed to move the clutch arm. Is your clutch working ok? The arm only needs to move a very small distance to engage or disengage the clutch. A common problem is to have the slave adjusted too tight causing the arm to be in constant contact with the release bearing. This will shorten the life of the bearing and clutch. You want the slave rod to just touch the arm when the clutch is released.

Randy

Unique 289 FIA
Southern Automotive 396
Team III 16's
Brilliant Silver

[Jim Harding]

Doug,

All things being equal, the slave should move the same distance whether connected to the clutch fork or not.... only the resistance or the force applied to the clutch pedal should increase, as you cannot compress the fluid in the system.
From what you described, either you still have air in the system or the clutch arm is prevented from further travel, i.e. binding.

If you have a large "C" clamp, try using it to disengage the clutch. It will give you some feedback on where to look for the problem as will at tell you how far the fork has to move in relation to disengageing the clutch.

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004

[dmiller]

i calculate the volume of the master cyl, 3/4 inch bore, and the volume of the slave cyl at 1" bore, and determined that slave cyl should move approxmatly 9/16 inch, what i'm seeing. i don't know where i got the 1" free motion. but regardless, i'm not getting enough movement at the clutch arm., i think i'll have to use a 13/16 diameter slave cyl.

doug

[spd4me]

dmiller
I have the same problem your having from time to time. One day it goes into reverse without any problem , the next it will grind. I've bleed the line and put thermo-shielding over the line to keep heat off. Bill Parham says to add washers between the clutch arm and the bellhousing. He says this will change the fulcrum point. It seems to me all that will do is move the fulcrum point back and forth and not change the leverage. I have thought about getting a new clutch arm and re-weld the lever closer to the slave cylinder end to increase the amount of travel at the throw out bearing or get a whole new slave cylinder set up. The problem with adding washers is how do you get your hands in the hole and still be able to see what your doing with everything already installed in the car.

[dmiller]

i've ordered a 1" bore master cyl. if what i read on wilwood's web page is correct, it might interchange without any difficulty with the existing 3/4 master cyl. if so, then the stroke will be a little more than 1".

wilwood also ofers a 13/16 dia slave cyl that might be easy to hook up. that's plan two.

doug

[clayfoushee]

Lee Dahmer would builds Uniques in this area, told me the grinding into reverse is a pretty normal with a hydraulic clutch set up on these cars. Does it get worse as the car, hence the clutch master fluid, gets hotter? You could be boiling (or close) your fluids given proximity to those headers. Mine's fine cold, but after extensive idling in city traffic, it always seems to grind into reverse.

Clay

Unique 9299, 427FE side oiler, top-loader (close), 3.31 rear

Annapolis, MD

[dmiller]

i'm pretty sure that i don't have enough stroke, i'm using a mustang style clutch housing and an aftermarket clutch. the mustang cable actuator that i measured, travel almost 1 1/2 inches. i had hard shifts and slipping clutch with only 9/16 travel.

i've only driven 5 miles, total, and it would have been almost impossible to make my current condition livable.

the clutch tech help line tells me i need 0.360 inches of movement at the throw out bearing. i don't know the pivot arm ratio, but if i'm only moving 0.563 (9/16) at the outboard end of the arm, i'm probably not moving 0.360 at the TO bearing.

crossing fingers that this solves it.

doug

[clayfoushee]

Yep....sounds like a different problem than the one I was describing. Shifting should be smooth in all forward gears, with an occasional grind into reverse when the fluid's very hot.

Clay

Unique 9299, 427FE side oiler, top-loader (close), 3.31 rear

Annapolis, MD

[Poorboy]

The washers will only change the distance the fork is from the bellhousing.
Doug,
You will also have a harder clutch.
Poorboy

[eliminator]

The grinding going to reverse in a top-loader is NOT normal[V]. I had a 62 406cu.in. in a 55 Ford years ago with a top-loader, never did have clutch problems. The Hyd. Throw Out Bearing in my 427 with a top-loader works excellent[^]. In 1,800 miles there has never been one grinding or clashing of the gears. I hear of alot of problems with the FE engine and slave cylinders for some reason. Not so much with the small and mid blocks. Tell Lee,(OC) for short he needs a hyd, throw-out bearing. Brent, you have one, any gringing[?][?]

Eliminator

[spd4me]

Doug
I contacted Wilwood with my problem and they said their #260-1333 slave cylinder (.88 bore)works well with their #260-1304 Compact Master Cylinder. Said it will give 1.38" stroke. I was by a custom car builder's shop (nothing less than $85,000, and up)last week and they use a CNC brand slave that looks like the Wilwood. The end with the nut attaches to the clutch arm and the end with the swivel hole attaches to a fixed object (in some cases the transmission). It pulls the clutch arm instead of push. There's aplace here in town that carrys the CNC brand I plan to check one out.

[clayfoushee]

Elim,

I was sloppy in my choice of words. I didn't mean and shouldn't have said it was "normal" or attributed that to my friend Lee Dahmer. What I should of said and did mean, which you also said in your note, is that it is "common" especially in big blocks like ours.

Now that we've gotten that cleared up, I'd love hear about the fix. Ours both happen ONLY after the hydraulic clutch has been well exercised in stop and go traffic, and then it's ONLY in reverse.

[B)]

Clay

Unique 9299, 427FE side oiler, top-loader (close), 3.31 rear

Annapolis, MD

[Brent]

Eliminator,

500 miles and no grinding yet.

Brent

[brfutbrian]

shouldnt the master cyl bore be at least as big as the slave cyl. ? i know you can go with a bigger bore on the master cyl.vs slave cyl. you need less pedal movement to move the slave cyl. i would think that a 3/4" master cyl. would only push a 1' slave cyl. 3/4 of its max travel. brian

[dmiller]

spd4me, that is the slave cyl i ordered today. looks like it will be ok, slightly resistance to push in the clutch pedal due to the smaller dia slave, but my clutch is very light now. should be ok.

brfutbrain, you are correct that a smaller master will push a bigger slave less distance, but the distance is a function of the the square of the diameter, so the distance will be even less than you might think.

but, i'm going to try staying with the original 3/4 bore master, and go to the smaller slave, so stroke will be more at the clutch, at the expense of a slightly harder pedal pressure.

thanks

[eliminator]

Clay,

I know Lee, so I can poke fun at him. Next time you converse with him tell him Rick said hello and hope to see him in May.

Eliminator

[brfutbrian]

doug, actually im running a 7/8' master cyl with a 3/4' slave cyl on my clutch. i changed the master cyl. from the 3/4" trying to cure my occasional grind going into reverse. it didnt do anything for that, but the clutch pedal travel & feel is much more to my liking. later, brian.

[clayfoushee]

Elim...will do. I think he's planning to be there, as am I.

Clay

Unique 9299, 427FE side oiler, top-loader (close), 3.31 rear

Annapolis, MD

[Mike Geddes]

Well, after reading all those tales of woe about clutches, I'm kinda glad I put in an automatic box.
Mike

Mike Geddes