BACKDRAFT SLAVE/MASTER CYLINDER cont.. Still having issues

[Jimbocobra]

I'm stumped. My Backdraft still get hard to shift when it gets warmed up, even in very cool 45 degree days. I runs perfect for a while.

So far I have replaced the slave cylinder, replaced the fluid with high tempurature racing fluid in the lines. I re-rounted the lines from the master to the slave cylinder up and over the footbox and wrapped the line in some heat resistant foam from Summit Racing. I have a heat shield below the master and in-fact, I added some pieces to existing heat shield to fill in any gaps. I have ceramic coating on the headers. It runs perfect until it gets hot. If I keep the car moving and air circulates, it tends to run fine - until I stop at a light - so it must be related to heat somehow. The engine temp on the car does not even have to get high, even at moderately low temps some type of failure starts occuring as heat builds. I have a Ford crate 392 that runs perfectly and only has 3000 miles on it.

I have no idea what else to do. I have been on every forum and tried every solution they have offer.

I touched the master cylinder and it did not feel very hot compared to the heat shield and headers so I suspect it may not be the master (but who knows?).

Is it possible that the I should put a heat shield between the engine and the slave cylinder to stop the heat from radiating to the slave? The slave is located next to the bellhousing at least a foot behind and underneath the engine. I am also considering wrapping the master in header tape or painting it with "lizard skin" to deflect heat. Any Ideas

[Cashburn]

What type of slave setup do you have?

[Mac VABCH]

Switch to a hydraulic t/o bearing and all your problems will go away. I have had good luck with Quarter Master bearings. Hydraulic T/O are harder to install and set up and my require the trans to come in a out a couple of times to get the setup right. I think most of the slave cylinder issues are related to the force and distance require to move the clutch fork to disengage the clutch. With a Hyd t/o the pedal stroke is shorter and there are no linkage issues to deal with. I don't think heat is the big issue. I still have my line in the original place next to the headers. I am using Castrol SRF fluid and the headers are ceramic coated. My car is track only and generates a tremendous amount of heat. Since I switched to a hydraulic t/o I haven't had any issues. Good Luck send me a PM if you want to talk about it some more...Mac

[Jimbocobra]

Thanks for your prompt reply. I am not sure what type of slave, I know it is not a Lakewood. I was hoping that I would not have to go to the T/O bearing because it sounds pretty expensive to pull the trans. But if that solve the problem and all of your lines are still in place next to the headers, sounds like it may not be a heat issue, but why is it only when the car gets hot that I have the issue?

[mln385]

Might be off base here but could it possibly be an interference problem in the tranny with improper clearance and lash?

What I am getting at is maybe once the transmission warms up the metal expands and has less clearance.

[madmaxx]

Do not go with hydraulic throw out. All the cobras I ever worked on 15 plus had the external slave and worked perfect. Is your slave pushing perpindicular to the clutch are? Have someone push in the clutch pedal and see if it is pushing straight, not at angle. If it is GCPC has a bracket that will get i perfect. Your enemy is not heat, DO NOT USE SILICONE brake fluid. if you have that is your problem.

[Jimbocobra]

I am using Royal Purple. Not sure if it has Silcone or not. I will call my shop and find out. The slave runs parellel to the ground. When we replace the slave we use part of a rocker arm to allow the slave to go straight in and out but still have some play. If it is not heat, do you think it is the placement of the slave? The shop told me that they felt that slave was meant to push and it is pulling or vice/versa - either way, they did not like the set up.

[madmaxx]

Go to the backdraft forum on this foruml, search slave cylinder. About the 4 th post you will see a bracket from GCPC, including slave it is $110. It will work perfect with your transmission and your problems will be gone. No rocker arm needed. I tried to cut and past but was unsucessful. Owners name is bill littleton.

[madmaxx]

Winter time is a great time to change out your slave cylinder fluid or change over to a more effective slave cylinder and bracket. The bracket and slave cylinder will set you back $110.00 but will offer a more effective slave cylinder action over most other applications. Please feel free to give me a call at 859-630-9099 or email at Bill@GCPERF.COM

[Jimbocobra]

Bill,
I will order it and call you tomorrow. I sent you an e-mail as well. Just one question, if heat is not an issue, why does it only happen when it gets hot and when I am not moving, like at a stop light. At this point, I could care less about the $110. I just keep ordering parts and taking it to the shop and everything I try doesn't work. I believe you, just want to understand it the heat connection if it is an alignment issue? You have worked on more cobras than anyone in the country I suspect - especially BDR's so if this and the fluid change will do it, okay with me - I just want to drive it without worrying that I won't be able to get it into gear - takes the fun out of it.

I may also order the powersteering kit and a soft top in time as well.

[Cashburn]

What type of bellhousing do you have?

[Cobra 29]

This bracket and slave cylinder orientation assumes that the long clutch arm is fitted. Meaning that it pivots on the passanger side of the transmission so the clutch arm must be moved toward the front of the car to disengage the clutch. The point is that this longer clutch arm requires more travel at the clutch arm tip to disengage the typical clutch. This arm was intended for a cable actuation. The clutch arm that pivots on the driver side requires less clutch arm travel and the push direction is toward the rear of the car.

I now understand the above because I have fitted larger clutch master cylinders to gain more travel from my slave cylinder that pushes toward the front of the car. I started with a 7/8 master but the slave travel was not great enough. Then to a 15/16 still not enough slave cylinder travel. And finally a 1" master that seems to be enough. One possible solution is to increase the diameter of your master cylinder IF your slave cylinder can physically support more travel.

Bill Littleton, I like your bracket and slave cylinder set-up. Will your bracket fit a Lakewood / TKO600 bolt pattern? What is the diameter of your slave cylinder? What is its travel length? Is the slave cylinder for a particular mass production car? Sorry, for the questions but you really need to know the diameter relationship between the master and slave cylinders to estimate the travel available at the slave / clutch tip arm.

[Jimbocobra]

I am not sure of the bell housing. I have a tko500 and the bell housing is aluminum - that's about the extent of my knowledge.

Why does it work fine until it gets warm?

[Cobra 29]

Jim, I believe that your slave / clutch arm tip travel is very close to the movement you need to completely disengage your clutch and when the parts are warm / hot they expand enough to remove this clearance that you have when the parts are cold. I believe this has happened on my car because I was continually on the "edge" of having enough travel to completely disengage my clutch until I fitted a larger master cylinder that increased my slave cylinder travel beyond just enough movement.

With your engine running and the clutch pedal fully depressed can you shift into reverse without any grinding of the transmission gears? How does this work when everything is cold and when everything is at operating temps?

Shifting into reverse from a stop and shifting into 5th while running when I did not have enough slave / clutch arm travel to completely disengage clutch always resulted in some gear grinding.

I also believe that as the clutch disks wears, we need to re-adjust the clutch arm to slave nut to maintain enough travel to completely disengage the clutch when the pedal is depressed and to have the least / no pressure on the throw-out bearing at rest (clutch pedal fully out / back).

[Jimbocobra]

When temps are cool outside, it works longer, but if I really get on the throttle for a while and go to reverse it does grind. Since putting the heat shield on and adjusting the clutch for a longer throw etc..., it does seem to take longer to fail. By the end of last year, it would get so bad that at a stop light I would have to keep a foot on the brake to keep the car from rolling forward. If I took it out of 1st, I couldn't get back into it so as the clutch would begin to fail the car would creep forward even with the pedal completely depressed. There is definetly some relationship to heat, the hotter the weather the sooner the failure and the hotter the engine, the sooner the failure.

[madmaxx]

He has bdr 357, bill littleton is a BDR dealear along with Cashburn. Run of the mill TKO500 and Ford racing engine. I have no idea what would cause someone to install a pull type slave cylinder set up on his car when 99% of the bdr's use the bracket style Bill has.

I have worked on alot of cobras not by will, LOL!!! I am sure a 5 minute conversation will Littleton or cashburn dwarfs my experience which is fine, i just use what works. It is so frustrating to hear about these issues which remove pleasure from the Cobra experience when the solution is very very easy.

The only item which needs to be confirmed is you have the right clutch arm, i know you have the right bellhousing, transmission, clutch master cylinder.

[Cashburn]

Not so fast. We use the pull type on 90% of the cars we build.

I am not convinced it is simply a slave issue. I believe there is a problem with the clutch, the fork, the alignment, and/or a combination of all.

But when you ask a question and get a couple "I don't knows..." then it becomes tough to help. Jimbo needs to contact his dealer and ask for some help or atleast determine what he has on his car for certain.

[Rick Parker]

Jimbo:

Cobra29 is right on the money in all aspects of your issue. The pedal ratio and comparative sizes of the master and slave are what will get this resolved. One item that has not been brought up is that when increasing the size of the master, a point can be reached (Fluid displacement) where the slave can be overpowered and the rod pushed out of the end of the slave and dumping all the fluid out. With careful planing this can be avoided. If this becomes a problem, a dimensionally longer (same diameter) slave will
cure this once the correct sizing has been arrived at. This is a OEM 289 push type setup, with the clutch arm pivot on drivers side, it works flawlessly. This is not a BDR car, but that really makes no difference. The components are working in harmony.

[madmaxx]

BDR's come turnkey minus. the clutch pedal, clutch master cylinder, brakcet and lines all come with the car. Proper sizing is done before it ever reaches this country.


I agree with Cashburn, give him or bill a call and they will get you on the right course. I imgaine your local mechanic does not see many cobras, where the dealers see 50 plus per year. I still feel the slave and bracket, push type are the way to go mainley because the only problem I ever had was alignment and once that was corrected all problems stopped.

Originally Posted by Rick Parker

Jimbo:

Cobra29 is right on the money in all aspects of your issue. The pedal ratio and comparative sizes of the master and slave are what will get this resolved. One item that has not been brought up is that when increasing the size of the master, a point can be reached (Fluid displacement) where the slave can be overpowered and the rod pushed out of the end of the slave and dumping all the fluid out. With careful planing this can be avoided. If this becomes a problem, a dimensionally longer (same diameter) slave will
cure this once the correct sizing has been arrived at. This is a OEM 289 push type setup, with the clutch arm pivot on drivers side, it works flawlessly.

[Rick Parker]

BDR's come turnkey minus. the clutch pedal, clutch master cylinder, brakcet and lines all come with the car. Proper sizing is done before it ever reaches this country

There are MANY variables on the clutch that could affect necessary changes in Master and Slave sizing ratios too.