Slave adjustment

[October-1881]

I'm having problems with shifting my SPF 351. I'm new to this so cut me a little slack. I noticed the other day that it seemed like the clutch was slipping a little. I called Eric at Dynamic Motorsports and he suggested that I start diagnosing the problem by adjusting the rod on the slave unit. I put a vise grip on it and moved the locknut from almost all the way at the end to almost all the way nearest the cylinder. We took it out and all seemed fine. So yesterday I decided to take it out for a (200 mile) long drive. After driving about 2 hours...I stopped to get gas and take a little stretch. When I started it back up, it seemed to go into 1st kind of hard. When I drove away, I couldn't get it into any gear. Finally while coasting down the on ramp, I managed to get it into 4th. and drove the last 2 hours at 50 MPH in 4th. Is it possible that when the car gets warmed up the reaction of the slave unit changes? Is the adjustment that critical that I should be moving the locknut to about half way? It just doesn't make sense that it can work fine one time and be totally not working another
time. This is very frustrating because I have good mechanical knowledge (ex-construction worker) but have never done much with cars. Someone told me there may be air in the line and bleeding the thing is nearly inpossible. I live in a area where there is no-one that has the equipment or knowledge to repair it and I'm not nuts about trailering it 600 miles to Cincinnati. HELP

[Mike Simard]

Did you flush the fluid yet? Your fluid is likely getting hot from the exhaust and is probably old, contains water and is boiling. That prevents the slave cylinder from releasing the clutch all the way and you car wont go into gear. You need the be able to do, or have done locally, maintanance as basic as bleed a clutch if you want to own a Cobra, there will be other little things like this down the road. Try asking a local auto parts store if they know anyone.

[October-1881]

What you say makes sense but it only has 3500 miles on it. If you still think I should flush it, how much fluid do I need to buy and what's the proceedure?
Thanks, Jeff

[Rick Parker]

Hey October!

A one pint bottle of DOT 3 fluid should be enough to replentish the entire amount in the slave and master. If you have an independent shop in your area that services imports sucha as Honda, Nissan, Toyota they should be able to help you get it adjusted properly since the hydraulic systems used for clutch actuation are fairly universal.

[TRIG]

I agree with Mike about bleeding the clutch. As far as the 3500 miles on the car goes that doesn't really matter. I had a similar problem with mine at 300 miles. If you can't easily get under the car you can actually bleed the slave from the top through the engine compartment (SBF required...lol) if you don't mind getting fluid everywhere. Mine wouldn't go into any gear, bled it at the slave and violla.

Mike,

Mike do you think wrapping the clutch hose in heat resistant tape would help keep the fluid from boiling?

Trig

[October-1881]

Thanks,
Are we still thinking it's the old fluid and the heat that's the culprit? I'm having a tough time thinking that 3500 miles and we're calling that old. Remember...I know very little about this stuff, just trying to make sense of it.
Jeff

[October-1881]

What does (SPF lol) mean? Does that mean what I think? Like lots of luck? The master on my car is verry accessible on the fire wall. The slave isn't too hard to get at. What's the proceedure?
Thanks,
Jeff

[TRIG]

I'm no expert either but maybe the fluid that's in there has a low boiling point so it's no neccessarily the fact that it's old but inferior fluid. I would start with changing the fluid because it's the easiest step in trying to sort it out.

Trig

[Mike Simard]

Even though the car has 3500 miles I would flush the fluid. Brake fluid collects water over time by just being there. As water increases the fluid boils easier which makes it spongy. The heat from the headers is close enough to the clutch line to cause boiling. Once the fluid boils it looses some of its future properties and will be more suseptible to heat. Since you need to bleed your clutch anyway you might as well bleed the heck out of it which will flush the lines. All you need to do is open the bleeder at the slave cylinder and replenish fluid at the resevoir, you don't need to deal with the master.If you don't have a helper, try a speed bleeder which is a check valve that goes on the slave bleeder, then you can just pump the clutch pedal many times occasionally getting out to replenish fluid. That should make a difference.

[TRIG]

(SBF) small block ford. With a small block you can get to it from the top...with a big block you wouldn't be able to get to the slave from the top. You'll see as time goes on that the big block guys like to make fun of us small block guys.

Have someone sit in the drivers seat push the clutch to the floor and hold it there, you turn the bleed screw letting the air and fluid out, tighten the screw back up, they release the clutch and start the process over again until it seems all the air is out. Refill your resevoir and your done. Make sure you don't totally deplete your resevoir and suck air into the system.

trig

[October-1881]

Thanks, you guys are making my day. This is great!

[October-1881]

Mike,
Do I need to put the cap back on the master when we're bleeding the line?

Originally Posted by Mike Simard

Even though the car has 3500 miles I would flush the fluid. Brake fluid collects water over time by just being there. As water increases the fluid boils easier which makes it spongy. The heat from the headers is close enough to the clutch line to cause boiling. Once the fluid boils it looses some of its future properties and will be more suseptible to heat. Since you need to bleed your clutch anyway you might as well bleed the heck out of it which will flush the lines. All you need to do is open the bleeder at the slave cylinder and replenish fluid at the resevoir, you don't need to deal with the master.If you don't have a helper, try a speed bleeder which is a check valve that goes on the slave bleeder, then you can just pump the clutch pedal many times occasionally getting out to replenish fluid. That should make a difference.

[Mike Simard]

Just leave the cap off until you're finished.

[zipzip]

October,

I'm not familiar with the Superformance setup, and flushing fluid is never bad advice, but you described changing the slave cylinder setup just before experiencing the problem - have you checked that what you changed is not causing the problem?

With my setup, the shift fork is pulled toward the front of the car by the slave cylinder. I just finished adjusting mine last night. The problem that I had is that the "zero" position of the cylinder was too far aft. When the cylinder stroked fully, it didn't pull the clutch fork enough to fully disengage the clutch. This meant that as I was sitting with the engine running and depressed the clutch and tried to shift to 1st, there was enough torque through the clutch to spin the transmission gears, and the car wanted to roll forward through friction as the syncro was engaging the gear. I couldn't get it into gear because the input shaft was spinning with the engine.

Perhaps your adjustment has caused the clutch to always be "partially" disengaged. After driving a while (and maybe spinning some), the clutch and flywheel are hot which reduced the amount of friction between them, and you had a similar scenario where the transmission didn't fully disengage? I know you were trying to adjust tighter, but if by moving the locknut shortened the cylinder "zero" point, then that would actually disengage the clutch more.

Hope this helps. Pics may come in handy if you can...

[October-1881]

I adjusted the slave linkage toward the slave so it would be fully engaged thinking this would stop the slipping. It certainly doesn't slip but the condition was almost the same before I adjusted it. The hot oil makes a lot of sense right now because it shifts perfect until it gets hot. I'm planning on bleeding the slave this weekend. I'll let you know the results. Thanks for your input.

Originally Posted by zipzip

October,

I'm not familiar with the Superformance setup, and flushing fluid is never bad advice, but you described changing the slave cylinder setup just before experiencing the problem - have you checked that what you changed is not causing the problem?

With my setup, the shift fork is pulled toward the front of the car by the slave cylinder. I just finished adjusting mine last night. The problem that I had is that the "zero" position of the cylinder was too far aft. When the cylinder stroked fully, it didn't pull the clutch fork enough to fully disengage the clutch. This meant that as I was sitting with the engine running and depressed the clutch and tried to shift to 1st, there was enough torque through the clutch to spin the transmission gears, and the car wanted to roll forward through friction as the syncro was engaging the gear. I couldn't get it into gear because the input shaft was spinning with the engine.

Perhaps your adjustment has caused the clutch to always be "partially" disengaged. After driving a while (and maybe spinning some), the clutch and flywheel are hot which reduced the amount of friction between them, and you had a similar scenario where the transmission didn't fully disengage? I know you were trying to adjust tighter, but if by moving the locknut shortened the cylinder "zero" point, then that would actually disengage the clutch more.

Hope this helps. Pics may come in handy if you can...

[bkozlow]

My only warning would be to remember that brake fluid is the most effective paint remover you have ever seen. When bleeding a system, I get from Home Depot a roll of 5/16 clear plastic tubing and attach it over the breeder and bleed into the plastic line. It lets you see the air in your system and place so it becomes the highest point in your system. When you are done squeeze it at the bleeder and remove carefully so as not to get any on anything on your car. The tubing costs about $2.50 a roll and when done I just throw the whole thing away.

bkozlow

[October-1881]

OK
So after procrastinating and worring about never ever being able to drive the car again, I finally went ahead with the bleeding process. Man, I read way to much and worried way more. I had this somewhere between hip surgery and a heart bypass operation.
Anyway, I got a Mighty-vac like Blas said I should get. my son told me to get some brake fluid cleaner (Thank God) and a bunch of towels. One good thing about having prostate surgery is they let you keep the hemostat when they send you home with a cathater. Still had the hemostat and I clamped it on the hose from the pump to the slave after I finished bleeding it. That saved me from wiping up more fluid on the garage floor.
Lots of dirty, dirty fluid got sucked out and a lot more air than I ever figured I'd see.
Bottom line...fixed.
Elapsed time (including all my screwing around preparing the operating room) 45 minutes.
Thanks for all your help.

[cdog]

Question: I have the same issue on a BBF Superformance. I'm not getting full disengagement. Clutch has probably not been bled in a while, if ever.

I read the procedure and understand BUT where is the slave cylinder and how do I get to it?

[MrMagoo]

I dont know if this is the normal location, but on my car its to the left of the brake master cylinder, which is drivers side behind the wheel well slightly below the top of the engine compartment. Its kind of hard to get to. If in doubt, follow the hydraulic line up from the clutch to it's source. Good luck.

[cdog]

Ok.. I think I see it. Where is the bleeder nipple?