86VetteBill

I've got the clutch master cylinder in my hand....I'm not sure direction to go now.

The beginning: clutch wouldn't disengage until the pedal was almost to the floor. This seemed to happen all of a sudden. The clutch fluid in the reservoir was very low and dark. The shop manual says to bleed from the slave which I did, and others say to "push" the fluid in from the slave into the master which I also did (watch out 'cause you'll overfill the master reservoir - empty with a turkey baster (and don't put back in the kitchen!!)). No change in the pedal.

Under the dash, the clutch pedal / rod connection is good. Watching the hose between the master and the slave, there's no expansion when the clutch pedal is depressed.

This points me to the master / slave cylinders. And, as I said before, I've got the master in hand and the guts right next to it. The master's walls look good - no scoring or scratches. I'm about to go out and buy the rebuild kit. But, how do I know if the master needs rebuilding or the slave?

Or should I just go after the slave now, too?

loiq

I'd do both. Trust me, you don't want to take this apart more than once as bleeding is such a pain.

I rebuilt my master and got a new slave. Chances are if the fluids as dark as you say one or both are worn out, as they are aluminum. Also, check the hose to make sure the soft part is good and not cracked or anything.

AGENT 86

My master started to loose fluid. I pulled the kick panel and felt around where the rod enters the firewall. Pulled my hand out and found oil on my fingers. Bingo, bad master. I bought the rebuild kit and it works fine now.
Start feeling around for wet spots

86VetteBill

I decided to pull both anyway. And bleeding by "pushing" the fluid up from the slave to the master wasn't a big deal with the Mighty Vac....

Where's a good place to buy the kits? I've called Napa: master = $32.45, slave = $12.99 and 3-5 days for both. Autozone doesn't carry the slave?, but the master was $21.99. I left a messge for the local Chevy dealer.

frank j. moran

look at that master cyl real close, if it has any corrosive etchings in it get a new one, get a mag glass. I tried to rebuild mine and it did not hold up at all, the slave was fine as I belive it is cast iron. Just my 02 get a new master...and I'm a guy who fixes everything that possible. Put the kit money towards a new one,

86VetteBill

Wow - Chevy says master = $251.55 and slave = $231.23

ses86vette

I put a new slave (Autozone $75) in my 86 and within 2 days lost my pedal again, so I put in a new master ((Again Autozone $125.) Everything works fine now. A Chevy mech. told me they always replace both at the same time because both have just as much wear on them. He also said that unless your Master is in PERFECT condition inside, a bebuild won't hold very long.

1986Z51

I rebuilt my '86 clutch master and slave cylinders last month after losing most pedal pressure over the course of a day. Didn't know whether the master or slave were bad; would have bought a new/rebuild if I was certain which ONE was bad but decided to repair both on a budget. Ordered repair kits for the master and slave from Parts America for something like $25 which included rubber pistons, seals (except for the big rubber slave cylinder boot at the bellhousing), and spring clips. I think GM discontinued the repair kits. Brake fluid was like mud and it was hard to tell whether master or slave was the problem. Cylinder bores looked good and the only place I saw wear was at the master actuator rod -- there's an eye that fits over the pedal shaft that wore to an egg-shape over time (wish it was included in kit...). I ended up greasing and rotating the rod 180-degrees before clipping it back to the pedal so the actuator rides on a less worn part of that eyelet (although there would still be some pedal slop if pulled up on it due to the egg-shape).

GM may have re-designed this clutch actuator-to-pedal attachment in late '86 (I have an 86E) since some parts catalogs list "84-88 clutch master cylinder -- 0.38 diameter clutch pedal bushing" and "86-89 clutch pedal - 86 2nd design". I didn't measure my diameter when it was removed but I remember it to be smaller than 0.38" and suspected that a new master cylinder would have also needed a pedal upgrade... Anyway, clutch hydraulics work as good as new after the seal replacement.

CAJUN ZZ4

Don't forget..Follow the Shop Manual's Bleeding procedure to a "T" ..The Slave cylinder "Must" again...Must be in the Vertical position in order for all the air to evacuate.

Trust me on this one.

frank j. moran

yes I had that problem also regarding the 3/8 dia. I removed the plastic bushing on the rod and it worked fine, not the perfect fix but I had no choice. The master is avialable from Corv Cent for a lot less then the numbur you quoted. I would rebuild the slave as it is a little more forgiving due to it's larger dia., if the bore is good rebuild it.

CentralCoaster

Low clutch disengage sounds like air in the system. It's a BITCH to bleed.

If your fluid is daark, flush all of it. I'd try a gravity bleed with the slave unbolted from the bellhousing. If either cylinder is bad, you'll lose fluid.

Also, if you replace one, i'd recommend replacing both. They don't outlive eachother by much. Kinda like a 90 yr old lady after her husband of 70 years kicks the bucket. Not much motivation to stay alive. A dying slave cylinder will kill a new master, because it allows clutch dust in the system. Carbon destorys the cylinders.

I've also been told a deteriorating clutch hose can blacken the fluid. There are no replacements to date (that fit anyways).

CentralCoaster

Stock slave and master are aluminum. Although cast iron isn't a bad idea for replacement. It'll last longer and be cheaper. This is one area where I could give a sh_t about weight savings.

86VetteBill

The clutch master and slave are aluminum. I found a website www.rockauto.com who has both rebuild kits for a total of $30 + shipping. Next day: $23... 2nd day: $11. I know what I'll be doing Friday.

How about that rubber boot dust cover that covers the end of the slave and the clutch housing?? Can I get that somewhere?

CentralCoaster

Discontinued. I think it's very important part though. Keeps debris and moisture and clutch dust out of the slave cylinder.

86VetteBill

I found a used one form $20. It looks to be a pretty important boot, since it looks like it helps guide the rod that gets pushed from the slave.

CentralCoaster

Most old school Chevys don't have any sort of boot here. the pushrod is located by divots in the slave piston and clutch fork... the internal spring in the clutch slave holds the piston against it to keep it from falling out when your foot's off the pedal.