96+ Internal slave on 95 external slave truck?

[Chillin Dylan]

Hey y’all. I’m trying to bleed the clutch in my 95 2500 with a 97 2500 engine and transmission. Both trucks had 454s and the NV4500. The 95 had an external slave cylinder, and the 97 had the internal hydraulic release bearing slave cylinder. The stock master cylinder is what I have in the truck, I just changed the line over to the 97 style. I can’t get it to pump up. The pedal has barely any pressure on it and it’s only right at the end. I can push it with one finger. I’ve done the hose into a bottle of fluid, and the two man method. I got a lot of air out of it and no longer get any bubbles in the bottle.

My question is, are the master cylinders different in terms of fluid volume? The 96+ style has a different mounting flange than the 95, so it would require some custom crap. I’d rather not do it if I don’t have to, but I’m worried that’s the issue.

Also, both trucks ran and drove great and had nearly all new, perfectly functional clutch systems before the swap. Thanks for your help

 

[MIHELA]

I would imagine they would have to be, with the different slave requiring a different volume of fluid to operate. As far as installing the newer master in an older truck I have no idea.

 

[Chillin Dylan]

An internal slave does require a different volume of fluid compared to an external? That’s what I’m unsure of. I can figure out the mounting

 

[Schurkey]

Buddy of mine has a Ford 3/4 ton truck with hydraulic clutch.

He put a new clutch master cylinder in it a year or two ago. Took FOREVER to bleed the clutch. In the end, I pumped the pedal like a madman; the clutch slave cylinder would eventually pump-up. It'd be good for half-an-hour, and then be crappy again.

Pump the pedal like a crazy monkey, clutch starts working. Good for an hour.

Eventually--about ten rounds of slapping the pedal to the carpet time after time after time...the air must have burped back into the master cylinder; and it's been good ever since.

We never did get a satisfactory bubble out of the slave cylinder when we tried to bleed it the "normal" way. And...I'm not the only one who's had problems bleeding the clutch cylinders, and had to resort to just pumping the pedal a zillion times without cracking the bleeder screw. There's a reason that they're selling pre-bled master/slave/hose assemblies where you never open-up the hydraulic system, you replace EVERYTHING.

 

[Chillin Dylan]

Buddy of mine has a Ford 3/4 ton truck with hydraulic clutch.

He put a new clutch master cylinder in it a year or two ago. Took FOREVER to bleed the clutch. In the end, I pumped the pedal like a madman; the clutch slave cylinder would eventually pump-up. It'd be good for half-an-hour, and then be crappy again.

Pump the pedal like a crazy monkey, clutch starts working. Good for an hour.

Eventually--about ten rounds of slapping the pedal to the carpet time after time after time...the air must have burped back into the master cylinder; and it's been good ever since.

We never did get a satisfactory bubble out of the slave cylinder when we tried to bleed it the "normal" way. And...I'm not the only one who's had problems bleeding the clutch cylinders, and had to resort to just pumping the pedal a zillion times without cracking the bleeder screw. There's a reason that they're selling pre-bled master/slave/hose assemblies where you never open-up the hydraulic system, you replace EVERYTHING.

I was doing that a bit too. Closing the bleeder, pump it for a minute or two, open it and keep pumping, and so on. I’ve ran about half a bottle of brake fluid through it now so it’s nice and clean lol

 

[Chillin Dylan]

I never had this much trouble bleeding when I replaced the external slave in the 95 before the swap. It was dumb because I had to pull the slave out and hang it down so the bleeder was at the top, but after a few, it bled fine

 

[smdk2500]

When I did my 95 I had to do the same as Schurkey. I would pump till my left leg gave up switched till the right one gave up switched with another person and they did the same and we switched back a few times. Had a guy that had a brake bleeder that used an air compressor to pull the fluid through. That gave a little bit of pedal. Still had to pump the crap out of it. Trans shop told me the same thing pump the crap out of.

 

[Chillin Dylan]

Update:
So I found out using the specs for both style master cylinders on rock auto that the bore sizes are exactly the same. 18mm or .709”. However, I did find a Wagner unit on rock auto for the 95 bolt on style that has a .904” bore. I’m gonna go ahead and order that and see if it makes a difference. I’m pretty well convinced that there’s no air in my system, but it still won’t disengage the clutch. At this point I have to assume there’s something wrong with either the slave or the master cylinder, even though they were both driving around fine 6 months ago, and the master is way easier to change than the internal slave lol

 

[Schurkey]

Did you kick the clutch pedal a hundred times before deciding there was something other than air causing the clutch to not disengage?

 

[Chillin Dylan]

Did you kick the clutch pedal a hundred times before deciding there was something other than air causing the clutch to not disengage?

Yeah probably more. I’ve bled a brand new external slave and brand new internal slave on GMT400 trucks before and neither of those gave me much trouble at all. I’ve been trying to bleed this thing for a week now, a couple hours a day