HELP ! Stuck Clutch Disc or HTOB Air Trapped??

[kitcarbp]

OK Guys, NEW SET -UP. I have set-up my McLeod HTOB with about 0.160 gap from PP fingers to bearing face when piston is fully seated (not extended) (McLeod quotes it needs to be .100-0.250) to allow for clutch disc face wear over time. Clutch and pressure plate was installed over 4 years ago on this new build without ever being tested and I wonder if disc is stuck to flywheel????. What I know: I can select a gear on the TKO 600 and start the engine and confirms clutch disc is engaged because wheels turn. I CANNOT depress the clutch pedal while engine is running and select a gear or grinding will result. I have noticed if I place a small amount of pressure on shifter handle into any gear (with or without depressing the clutch) it begins to rotate the drive shaft and rear wheels when up on stands. How do I tell the difference between a stuck clutch disc or a HTOB that needs to be bled some more ? (I can see the HTOB travel about 1/2") but Im not sure if thats enough. What say the experienced ones out there ?
1) Do I run the rear wheel speed up to 70 mph in 4th on jack stands and while clutch is depressed, stab the brakes hard to try to free the disc ?

2) I plan to try to bleed one more time but my pedal is firm and feels good and bearing is moving into pressure plate fingers Im just not sure if its enough.

[tcrist]

DO NOT run the car to any speed on jack stands. You take an awful chance of it falling off of the jacks and running through something or actually hitting someone.

My guess is that you need more travel of your through out bearing. How you are going to do that I am not sure. You might need to change the clutch master cylinder to a different bore.

[kitcarbp]

I ran the car in gear in the air to warm up trans and rear axle fluid to check for leaks and all is OK so far. I have heard others claim light oil like wd40 is OK to use to soak a stuck clutch disc a little to help break it free if its stuck because once you put heat into disc with use, the wd-40 will mostly evaporate and not harm the dual friction material. I am using 500 series Mcleod disc on SS Mcleod flywheel (Ford Racing). Who has tried this or other light weight lube to unstick the disc ? Never been here before, any others been here ? Thoughts appreciated

Thanks

update: i Confirmed my disc is not stuck, it just appears I need more concentric slave movement.

[lal Naja]

Does your clutch pedal have any of the following options:
1: A travel stop? If it does you can adjust it for more travel.
2: Additional holes in the pedal for push-rod mounting. If so, move the rod away from pedal pivot to get more travel into the master-cylinder.

Also try to reduce/eliminate any gap betwen the pedal pushrod and master-cylinder to maxamize the fluid displacement. With a little luck you may be able to have the slave-cylinder move that little extra to create the gap between clutch disk and pressure plate.

If you do not have the above choices you will have to increase the bore if the master-cylinder.

Good luck with it.

Arthur

[kitcarbp]

OK , After some experiments , I confirmed the clutch disc is free to turn and not stuck to flywheel. I also confirmed my Wilwood 3/4" Master cylinder is stroking 1.00 inch as it should according to McLeod. At 1 inch of master cyl. stroke my pedal bottoms out on the pedal stop as designed. and Mcleod claims HTOB piston travel is max 0.890 when using a 3/4" master with 1.00 inch stroke.

I also confirmed from the Mcleod clutch instructions the PP fingers should be depressed about 0.375" to disengage clutch disc. EDIT: WRONG INFO: .375 is when it begins to lift off pressure plate, it needs close to a full 0.500" for complete release !!!!! I am now thinking there is still air in the HTOB system that is not allowing the full .375" movement, I can't easily reach into bell to measure HTOB movement but it looks (via a mirror) HTOB piston moving closer to 0.250" but not sure till I try to measure it with a stiff piece of wire or some other gauge.

It appears that the air gap @ disc is just not enough to completely stop the trans input shaft from turning when trying to shift gears, so ive determined the HTOB its definitely not pushing the pressure plate fingers far enough yet. Mcleod quotes an air gap should be 0.050" between disc and flywheel. but I cant get into measure it easily. Will need to make a feeler gauge 2 feet long to get in there. I'll post an update when its solved.

UPDATE
I just read that the Wilwood 3/4" master cly can stroke up to 1.10", I have mine set to 1.00" with my pedal stop since I am so paranoid to over-stroke the HTOB piston past its seal after all the horror stories I have read. Seems I need to ensure all air is out first and if needed get the extra 1/8" of master cyl travel.

[tkb289]

Sounds like you are on the right track … for a gauge, try a strip of sheet metal and different thickness 'tips' that are firmly attached, made of wood or plastic scraps, as kind of a feeler gauge.

[kitcarbp]

tkb I was thinking the same thing. I am trying to measure bearing travel through the bellhousing with what use to be the OEM clutch fork hole, I can only see this by using my mechanics mirror Mcleod also recomended (in the fine print of course) to drill a hole in the bottom of the OEM bell housing to allow easy disc air gap measurements during clutch set-up to ensure 0.050". I should have done this to make measuring easier in hind-site. Now its a little trial and error. Lesson learned.

Arthur, Since I am using a concentric slave, if I increase the master cyl bore beyond 3/4", yes I'll get more fluid displaced per stroke, but the concentric slave will over extend (beyond the design limit of 0.500" and leak. EDIT May 2011 : I was wrong, even a 13/16 bore will not over extend the htob piston with 0.160 initial gap to PP fingers. I did the math then measured it on the car. The pedal stop of course can control this. Mcleod claims the 3/4" master cyl is all thats needed to get the 0.500" travel from concentric slave. I need to prove to myself that I am already @ 0.500 concentric slave travel, ( be bleeding again and measuring the travel) which I haven't done yet, before I go to the next step. I figured I can make a gauge using rigid copper house wiring to check for 0.375" travel at bearing. What I need is a telescope gauge on a flexible handle. Hmmm necessity is the mother of all invention as they say.

Thanks all

[lal Naja]

Good luck with getting it resolved.

I've recently installed a HTOB (Hydraulic Throw-Out Slave/bearing) on my TKO 600. And I made sure I "measured twice and cut once" to get everything setup correctly. I was not pleased with the conical shimming washers that came with the HTOB. So after taking all the measurements I machined a solid metal spacer and tossed the washers.

I also made sure that the bleed line pointed up so that all air would collect at the top and evacuate when bled. I drilled a hole in the top of the bellhousing for the bleed line and welded a steel shroud to hold the bleed line firm and vertical. Bleed valve in the top of the hose made bleeding a one man operation with 100% success.

Have fun,

Arthur

[kitcarbp]

So I made a crude GO NO-GO gauge from copper wire and I measured the total movement of my Mcleod HTOB and my crude wire "gauge" measured about 0.390" of HTOB movement for my total clutch pedal travel to the floor board. The Mcleod info i have, states 0.375" PP finger movement is required to release the disc. This make sense so far because, I also placed the car up on ramps while in gear with engine off and confirmed the clutch disc does in fact release upon pressing the clutch pedal down about 3/4 way, and the car rolls off the ramps. I still have just 1.0" of master cylinder travel compared to 1.10" possible. I also confirmed I would have to remove my pedal stop completely to get more than 1.0" stroke at the MC. May try this tonight to get 1.1 " at MC to see if I can get 0.420" or more total travel @ HTOB. It seems the PP is not fully releasing the disc and keeps spinning the input shaft.

I also attached my Mity-Vac brake bleeder hand pump to the HTOB bleed line and tried to pull any trapped air out of the assembly. After pulling more than 20 oz. of fluid through it with the Mity-Vac hand pump , I am still seeing air bubbles coming out of the bleed line! (reservoir was always kept 3/4 full, it never dropped too low during the bleed process)

I am still stumped, where is the air coming from ? I have yet to try the old fashion pump the pedal and bleed with a helper. Do I need to go back and open the Master Cly bleed screw on my Wilwood MC and re-bleed the MC ? My belief is that @ 0.390" its still not enough PP movement to completely stop the input shaft from turning. I can still move the HTOB bearing another 0.120" before I over extend it, 0.500" is max travel of the HTOB according to Mcleod.

What I have not confirmed yet is if the HTOB piston is moving proportionally
to the MC stroke of 1.0", if it does not, its got air in the lines (which the bubbles are confirming) Dah !.

I'll be back at it this week, any other tidbits appreciated.

Thanks

[cdnus]

Did you grease up the bleeder screw threads?
When using a vacuum bleeder you will usually suck air @ the threads making it appear you have air in the system.

Craig

[lal Naja]

Try using a speed Bleeder (link below) it makes bleeding a one-man-operation. The threads have a compatable thread sealer on them and it has a one way pressure relief valve built-in to allow air and fluid to exit only.

I bled my HTOB in about five minutes with no help. I love it

http://www.speedwaymotors.com/Speed-Bleeders,942.html

Arthur

[tkb289]

Originally Posted by cdnus

Did you grease up the bleeder screw threads?
When using a vacuum bleeder you will usually suck air @ the threads making it appear you have air in the system.

Craig

This is a good tip and an important place to look ... air at the threads ... but be sure to use the correct pipe dope or other substance that is compatible with the clutch system components and fluid.

[patrickt]

Originally Posted by tkb289

This is a good tip and an important place to look ... air at the threads ... but be sure to use the correct pipe dope or other substance that is compatible with the clutch system components and fluid.

We used to call it "Rubber Grease." It would come in teeny weeny little containers, and I vaguely remember them being red. You never see it in the auto parts store anymore -- ever. You'll probably have to pick it up off the internet and you would generally use it when rebuilding a master cylinder (clutch or brake).


EDIT -- Here you go, this is what I'm remembering. LUCAS Red Rubber Grease.

[xlr8or]

Are you sure the snout of the input shaft isn't bottomed out in the crankshaft?

[kitcarbp]

Thanks you guys, after I posted , I thought, THE BLEEDER SCREW! MAKES SENSE.

No, I did not put sealant on it (did not even occur to me !!) and I bet thats exactly where its bringing the air in when I'm pulling vac through it.

xlr8or, I thought the same. When I set up the trans on the Bell Housing and engine , I did confirm I had enough clearance to the BOTTOM of the crank pilot hole, (even with my OEM motor plate ( I think its 0.070 thick)) but its a tapered hole (behind the pilot bearing) and I am beginning to wonder if I measured in the wrong spot and the input shaft nose is riding on the crank pilot hole radius area since I know its not bottomed out. The other possiblity is my concentric measurements were wrong , but the roller type pilot bearing I am using should be toasted by now if the input to crank concentricity is off, and I would have expected trouble assembling the trans to engine if concentricity is off, I measured total 0.010" off center concentricity which is at the upper limit but should be OK right ????. One way to check/diagnose input shaft to crank pilot clearance I guess is to loosen the bell housing bolts a tad and place "U" shaped shims between the bell and engine block at each bolt location to see if this solves the issue before I pull the drive train out to measure again. Of course than starter must be shimmed same amount and HTOB must travel a little further also. Input shaft dragging on the crank is the only logical thing left after I confirm I can get a little more than 0.400" HTOB piston movement.

Thanks for your input

[roadrod2000]

If you are useing the 1300 series HTOB the max movement from full compresion to full extention is .89 inch. With the 3/4" MC and 1.1" available stroke I don't think you can over extend the HTOB even after you add the .1-.3 inch clearance. Check my math and then losen that pedal stop

[kitcarbp]

ROADROD, Your math is right. On my long D.C. area commute home last night (and after reading other Mcleod clutch users posts, it occured to me, that I dont have enough Mcleod 1300 series HTOB movement yet. Although Mcleod states "0.375" Pressure Plate finger travel required" I believe that is for "initial" disc release, not "full" disc release, thus that is why my disc is still dragging on PP and not fully released @ my measured 0.390" HTOB piston movement. I think I get it now.

I also found an email from Mcleod on their web-forum where they expect FULL disc release at 0.500" HTOB piston travel, thus, now I see is the source of my confusion. If I would have been a little smarter, and drilled a hole on the bottom of my OEM bell housing, I would have seen that I dont yet have the desired 0.050" air gap between PP and disc at 0.390" piston travel.

You are spot on about 3/4" master and the bolt on HTOB, I wont over extend it with 1.0 or even 1.1" of travel with my current clutch pedal geometry after looking at it upside down via my mirror under the car last night.

I also realized the kit builder (West Coast) installed the clutch pedal stop after years of selling some cars with 7/8" Masters (For Tilton HTOB) that would in some cases over extend the HTOB (slip-on style) bearing if used on a Mcleod HTOB without a pedal stop. When they started supplying pedal stops on the kits, they also realized 3/4" masters are a better choice for pedal effort and preventing over-travel, they left the pedal stop in place (which I now realize was likely intended for using a 7/8" Master to protect from over-stroking the HTOB and leaking. I will now remove the pedal stop (that will give me another 1/4" of pedal travel and move that HTOB piston travel closer to 0.500" I think.

Thanks to all for your posts, its becoming more clear to me now. I love this Forum and could not do this project without all the help I have received.
I will report back in the next days.
Bill

[kitcarbp]

Ok the update is after removing my clutch pedal stop completely, this gives me the 1.1" of travel now on the clutch Master cylinder (3/4" bore). The HTOB now moves about 0.450" after contacting the PP fingers. It was too late to fire up the car and scare the neighbors last night so I will test if the 0.450 is enough to completely release the clutch disc now.

Bill

[roadrod2000]

Bill,
If it come down to splitting hairs (and it might) your next choice for MC is not 7/8, I know that Tilton has sizes in between 3/4 and 7/8, not sure about Willwood. The jump to 7/8 is pretty substancial, in terms of volumn of fluid, and may have more pedal effort required than you would want. If the 3/4 MC won't do the job take time to calculate the the exact size you need with the info that you have.
Rod

[patrickt]

Originally Posted by roadrod2000

The jump to 7/8 is pretty substancial, in terms of volumn of fluid, and may have more pedal effort required than you would want.

Not really. My Tilton 7/8 really doesn't have any more noticable pedal effort than any other big clutch car I've driven. Pics of it are in this recent thread (where I had to remove it) So, Should I Replace This Part or Not?