Clutch Pedal Goes to Floor

[siguy8]

I've got a 1982 I4 with a 5 Speed Manual Transmission.

My clutch gives no resistance when I push it down. I was under the car before it completely quit, and I watched as the slave cylinder worked normally for the portion that had normal resistance on the pedal (the last inch or so). The part that had no resistance (now the whole range of the clutch) had no effect on the slave cylinder. I've been looking at the master cylinder as I push the clutch, and the shaft moves down into it normally, but nothing happens past that. There is a little leaking happening inside the firewall on the master cylinder. I bled the clutch according to the TSM (open valve, push pedal, close valve, release pedal, repeat until there is no air coming out), and that had no effect on this issue.

I read on another post that "Seepage indicates that the rubber cup in master is worn out and bypassing fluid thus a lose of pressure to operate the slave."

What is this rubber cap, and will this require taking out my entire master cylinder to fix it?
How hard is it to remove and replace a clutch master cylinder (and does the brake master cylinder have to be removed as well)?
Will I need some sort of rebuild kit to fix this?

Thanks for any clutch-related advice, or tips for taking care of this. The sooner the better since this is my daily driver and I work daily.

[siguy8]

Thanks Casper. I ordered the master rebuild kit, but he didn't know what size they had. I'll find out Wednesday...

[siguy8]

It turns out that there was some confusion as to the availability of this rebuild kit. No one seems to have it. Any help on where to get one would be appreciated. Is there some more common car that uses the same one? The spring inside my master was broken, so I definitely need some sort of rebuild kit...

By the way, I measured it at 11/16".

[craigp29690]

By all means rebuild both the master and slave.  It will prevent a second failure down the road.

[mick]

Once you get it all sorted out, put silicone brake fluid in it if both cylinders have been rebuilt.  I used to have problems with the cylinders seizing if the car sat for a while, now I can leave it sit indefinitely and the pedal feels great.  Just a thought.

[siguy8]

The pain continues... Just got the master and slave rebuild kits from RockAuto, and the master cylinder one is completely wrong, plus it doesn't have a spring like they promised.

Casper, any luck measuring yours, and does it come with a spring?

I think it'll work if i can just get a spring...

[RookieAMC]

Hey yall, long time no post... I am having the same the issue that siguy8 had, does anyone know where i can find the proper replacement master cylinder for the 81 sx/4 with the 4 speed and the 2.5L engine. It seems like in the short life span of the eagle, amc decided to change the clutch setup 435874203854 times so i am having one h#@l of a time finding the right one

[siguy8]

I don't have any ideas on where to get the master. Rock auto gave me the wrong one, so be careful ordering one on there. If you've bled it correctly, new parts may be your only option.

Here's what I ended up doing in case you can pick something helpful out of it. I pulled the whole master out and took it apart. I found a busted spring in it and a bunch of bad seals. Replaced what seals I could get from the rebuild kit I bought and started looking for a spring. I found a decent one in Home Depot by the screen door parts. Cut it down a little and threw it in. It's still working great today. My only problem now is that I have to add clutch fluid about once a month since it still leaks a little.

I'd be interested to hear what your findings are on the master cylinder. I should probably fix it correctly some day...

Good luck!

[lapoltba]

I didn't want to chance getting the wrong one from rockauto so I think I got it from Carquest (regional parts store/distributor in the northeast US) and got the right one. 

I replaced the master, slave, and line all at the same time since it had been sitting 15 years and was all crudded up.  The parts aren't that expensive so I recommend doing it all at the same time.

[carnuck]

It depends how yours mounts (vertical bolt pattern, horizontal or angled) and the bore diameter. I found many were actually early Toyota or XJ cylinders

[RookieAMC]

Iapoltba, just to verify, you have an 81 with the 2.5l and the 4 speed trans?

[lapoltba]

no, sorry for the confusion.  Mine is an 83 sx4 with the I6 and t4.  So there might be differences there.

[RookieAMC]

Yes see thats the problem, the 6 cyl and the 4cyl have different clutch assemblys

[captspillane]

No, they don't. The six cylinder assembly is identical and interchangeable with the four cylinder version except for the length of the slave cylinder pushrod.

The pushrod slides out of the rubber and the old one slides right into the rubber and against the piston inside. My 2.5L Kammback has the entire system swapped from a 1983 4.2L except that pushrod and the tube resevoir.

I have personally purchased a new six cylinder master cylinder from Rock Auto multiple times. I have gotten a wrong one. I've gotten a large number of right ones. For some time a few years back I could not get any at all from Rockauto or any other place because they stopped production. Since that time period they've become available again and I got several. It is unreliable, but not a showstopper. I've now got six extras for that reason.

[carnuck]

Just an FYI, but if you use any fluid other than synthetic brake fluid or Castrol GTLMA brake fluid in them, they won't last long. Most are made with natural rubber seals which self destruct with modern fluids which are caustic to them.