Slave Cylinder Replacement

[Dest]

I replaced my slave cylinder on my 96 XJ, opened the mc and manually pumped it. My friend who was watching the mc said he didn't see any bubbles come out, but it definitely sounded like air was exiting somewhere and eventually it went away so I pumped some more and then figured it was good.

Now it's the same as before, if the Jeeps turned off I can go in and out of gears, as soon as it's turned on it can't go into any gear but can grind against reverse.

Something different or did I miss something?

 

[Ecomike]

At one point I had to get under the jeep and manually return the slave to the open position after each pump to actually get the air all out of the SC, even with a one man or 2 man bleed operation on the SC. Then days later my tubing failed (rubbed a hole in the side where it got too close to sheet metal), and that time I had to bleed the entire new tubing, an I tried something new, I just pumped it about 500 times very rapidly (and topped off the MC about 4 times), with out using the SC bleed valve. The fluid turned into a foam, but it got most of the air out. I repeated that an hour later and it has been fine ever sense. But had the cap on the MC, sealed while pumping!!!

 

[Dest]

I think we did get some air out if we left the cap on and pumped it a bit, but after so much pumping I think it might be something in the tcase itself.

 

[Matthew Currie]

Usually it should sort itself out eventually but as Ecomike found, it can take quite a few strokes.

However, you can help it along if you dismount the slave cylinder from the housing, and push the rod in as far as it goes and then carefully let it back out. You can push it in manually further than it goes when mounted, and when you do this, it should displace a tiny bit more volume than there is in the lines, making for a full or nearly full bleed. Make very sure that you don't allow the rod to come out too far, though.

 

[Ecomike]

Usually it should sort itself out eventually but as Ecomike found, it can take quite a few strokes.

However, you can help it along if you dismount the slave cylinder from the housing, and push the rod in as far as it goes and then carefully let it back out. You can push it in manually further than it goes when mounted, and when you do this, it should displace a tiny bit more volume than there is in the lines, making for a full or nearly full bleed. Make very sure that you don't allow the rod to come out too far, though.

That makes a lot of sense, even standing it on end with the bleed valve on top while doing that might help the air rise to the bleed valve in the process. I was convinced at some point that the SC was trapping air back in the rear, and not moving in and out during the bleed, especially with the bleed valve open, your post confirms it!!!

 

[Matthew Currie]

That makes a lot of sense, even standing it on end with the bleed valve on top while doing that might help the air rise to the bleed valve in the process. I was convinced at some point that the SC was trapping air back in the rear, and not moving in and out during the bleed, especially with the bleed valve open, your post confirms it!!!

ON the 95 and 99 I have (including the Centric aftermarket replacements), there is no bleed valve. Thus displacement is the only way to get it bled unless you dare to drill through the blind bleeder hole.

 

[Ecomike]

Mine is actually the Nissan SD22 diesel/transmission combo transplant, 85 Frankenjeep, LOL, it has a bleed valve.

 

[Dest]

Yeah I did notice that my "bleed valve" on the bottom doesn't really seem to be functional unless I feel like drilling through it, which I don't lol.

 

[gradon]

I drilled through the blind hole and put in the bleeder valve from the old one(been running it for some years like this). I think my seals on the current master are on their way out cause I feel a hitch near the top of the initial push sometimes like the pressure is escaping a bit(prob shouldn't use synthetic).

 

[Matthew Currie]

I drilled through the blind hole and put in the bleeder valve from the old one(been running it for some years like this). I think my seals on the current master are on their way out cause I feel a hitch near the top of the initial push sometimes like the pressure is escaping a bit(prob shouldn't use synthetic).

If you're feeling a hitch, and yours is a pre-97, check the arm on the pedal that engages the MC. The weld can fail, and then the arm bends. When that happens it eats the master cylinder. Later ones dropped that arm in favor of a more modern and direct mode of failure (the bushing falls apart, eats the retaining clip and then the push rod just falls off the pedal at some randomly inconvenient moment).

 

[Ecomike]

I found synthetic eats the aluminum MCs faster. I have gone to steel MCs and SCs when and where I could find them on brakes and clutches.