gdl2165

Car is a 96 LT4 convertible with the ZF6 transmission. I'd been having an issue with the reverse light switch working intermittently so today I pulled the switch to clean it. To accomplish that I removed the nuts from the slave cylinder and removed it from the bell in order to get room to get my hand up in there. I didn't disconnect the fluid line, nor did I do anything with the bleeder valve. When I put it all back together I now have no clutch pedal pressure. I pulled the slave back down (twice actually) to verify the rod was in place and located correctly on the clutch fork. No problems found there. I checked the fluid level, it's dirty and was down to the add mark so I topped that up but I don't feel it was low enough to have caused an issue. I last drove it about a month ago and it was working perfectly fine at that time. I did not try it before beginning work on it today so I can't guarantee that something hadn't gone bad in the meantime but I'd give that possibility very low odds. I think I've somehow introduced air into the system but I don't know how that could have happened. Anyone have any ideas on what may have happened and/or suggestions on fixing it? At the moment I'm thinking my next step is to get a pressure bleeder and push fluid up from the bottom to bleed it and get fresh fluid in there.

Lt4-396

It's extremely easy to have the slave cylinder rod slightly Cocked and miss the part inside the bellhousing, especially when the Trans is still in place.
I took me 6 tries to finally get it correct.

If the pedal has zero pressure than it is not installed correctly.

billschroeder5842

Get a buddy to sit in the car while you mess with the slave, from underneath. Since it is only two bolts that are relatively easy to get at your can pretty quickly loosen bolts and move the slave slightly, while your buddy pumps. When you make contact/pressure keep tightening and "check pumping"

You got it!

gdl2165

I'll check it again but I already pulled it back out twice to verify the rod was located correctly. When mounting the slave back to the bell it doesn't just slip on, I do have to exert a small amount of pressure on it to get it to compress the rod into the slave so I know that rod is pressing on something.

MatthewMiller

That makes me believe you do indeed have air in the system. Time to bleed it. I found that matter what method I used for bleeding, I still didn't a firm pedal until I did what I think is referred to as the "ranger method" of bleeding: push the clutch pedal all the way down and hold it there for five minutes. Then let your foot slip off the side so the pedal pops back up. Then rapidly press and release the pedal 50-100 times.

billschroeder5842

Curious, what would cause a otherwise well functioning clutch to get air in the system with just the slave removed for a brief time?

I'm still thinking that it is an alignment issue... but thats my .02

MatthewMiller

I'm not completely sure. I also wonder if there is a seal that's messed up or other issue caused by dirt in the fluid that got jostled? I know exactly what you mean by alignment issues. But I am thinking that if he is encountering some resistance as he threads the nuts down, then the rod has to be contacting something. Otherwise, the preload spring would cause any resistance to the slave being pushed all the way down on the studs.

Another test to verify this might be to clamp the end of the rod to the slave casting with a beefy C-clamp, and then repeat the pedal test. That way, he would know that the rod is not moving freely. If the pedal is still limp, then he know that misalignment of the rod is not the issue.

Hmm, for that matter, I wonder if the pedal linkage somehow came disconnected from the slave cylinder input rod? gdl2165, look under the dash and make sure that the clevis for that rod is still positively attached to the pedal assembly. Make sure that moving the clutch pedal moves that rod.

old_vette

I had this problem after replacing a leaky slave cylinder.

After bench bleeding and assembly, and adding fluid to the reservoir with slow pedal pumping and bleeding at the connection to get fluid to the slave after remounting to the bell housing by my wife, I had no pedal pressure.

After pumping the living daylights out of the soft clutch pedal for 5 minutes solid, the pressure returned - higher and more solid than ever.

gdl2165

I actually did try the first part of that, I didn't read to do the 50-100 times afterward though. I'll give it a shot.

gdl2165

That's exactly what has me confused as well, I just don't see what could have caused air to get in unless maybe the slave just happened to fail at this time. I'll still check for an alignment issue but it'll probably be this weekend before I'll get a chance.

gdl2165

Interesting though on the c-clamp, I may give that a try.
I'll check the pedal linkage but I was nowhere near the master cylinder or the pedals so if it has come loose then I'd feel extremely lucky that it happened in my garage and not on the road.

gdl2165

Could be worth a shot as well, I'm open to any and all suggestions.

As I said, I probably won't be able to get back to try any of this until Saturday.

gdl2165

Well I found my problem. I went out to the garage to see if I could get it to bleed and found the master cylinder was really low. Look under the car and sure enough there's a small oil spot. Climb underneath and there's a drop of fluid where the slave bolts up to the bell. The front end was still up on ramps from last weekend so the fluid was able to drain out rather than just pool in the bell. So, time to replace the slave. My first choice was to send it off to Power Torque Systems for a rebuild but their website isn't working. Does anyone know if they closed down? I hate to go buy a crap aftermarket unit but I may have to.

billschroeder5842

Glad you found your problem

llesg

Jim at power torque systems told me he wasn't renewing his website due to lack of parts or demand for clutch kits but that he was going to continue doing cylinders.
his number is (641)342-7446
good luck!!

gdl2165

Excellent! Thank you for tracking that down. I installed the one from O'Reilly's and it's working fine but I'll give Jim a call and see about getting the original rebuilt if it's not too terribly expensive.

mtwoolford

Is this the future for C4s? If so, it's news I didn't need to hear.

DGXR

Maybe, possibly... when the slave was removed and being moved around, the hydraulic line between the master and slave developed a crack? Was the line flexed at all when moving it around? It would explain the low fluid and the lack of pressure. Check for leaks... just thinking out loud here! Good luck

gdl2165

It was definitely leaking from the internal seals. The replacement slave I installed is working perfectly and the fluid level is holding.