Do I need a new master/slave cylinder?

[joel]

Truck: 03 2500, 118K original miles, no mods, NV5600, original clutch, some towing with it, but nothing brutal, no visible leaks on hydraulic lines and reservoir seems to be holding fluid

Last night my truck suddenly wouldn't stop with the clutch pedal pressed to the floor. Fortunately, I was just starting to move, but I had to hold the brakes to get the engine to stall. I couldn't even pull the shifter out of gear.

I managed to get it home OK, but when I slowed to enter the driveway, same symptoms. Clutch would not disengage and had to stop by stalling the engine.

Plenty of fluid in the reservoir and all the lines looked good. Except this, when I crawled underneath. Is this fitting pulled apart? Is the hydraulic system toast? Or is this OK and maybe I just have an air bubble in the system?

 

[Darkbloodmon]

If you're foot is on the floor with the clutch pedal and you can't take the shifter out of gear you don't have a bubble, the clutch pedal when functioning is applying a massive amount of multiplied hydraulic force to the clutch diaphragm. Any leak after the master cylinder is going to cause an issue when applying the clutch pedal since fluid will be pushed out. The system is intended to be sealed, a bubble or air developing in the lines is indicative of a system failure.

You can put a paper towel over the line where you think it's leaking and push the clutch a few times to confirm but the options on the table are essentially replace the master and slave assembly, Or pull the transmission. I wouldn't suspect a clutch(mechanical failure) at that mileage. A seal failure on the hydraulic system is much more likely and reasonable considering the age of the truck and low mileage.

The aftermarket slave and master assemblies are all pre-bleed and non serviceable systems. Not sure if the OEM unit was like that but everything after it is.

 

[GCroyle]

Joel,

That is a quick connection that has mysteriously disconnected. I'll call that a bit rare. If the history on the hydro's is fuzzy might just be easiest to hang a new prefilled system and call it good. Once that connection has disconnected then I'd be very suspicious about its future stay connected status if you got it to reconnect.

Good luck

Gary

 

[joel]

Thanks. That connection is not moving. I suppose I could get big tools out and try to force it, but I agree that it'd always be suspect afterwards. Time to order a new hydro system. Any reason to order the $350 southbend vs the $140 Luk system?

 

[BigPapa]

I recommend the SBC, that's what I ran, but the Luk is the OE system I THINK.

 

[CrewCabDiesel]

Agree SBC is the people to talk to. Have you pulled out the slave cylinder out of the bellhousing yet? Its not hard to get out,(do not disconnect the hydraulic line) once out, see if its leaking, if not compress the rod in the slave cylinder having someone watch the reservoir for air bubbles, if you have air there is a leak somewhere. if not while holding the slave cylinder rod compressed into the slave cylinder, have someone very slowly press the clutch petal little at a time and see if the slave cylinder rod moves, (dont push it too far, an solid movement of an inch slave cylinder rod is good enough) you have clutch issues.

 

[joel]

Well, I replaced the system today. Went with Luk since I just didn't have $325 for the SBC right now.

Two questions:

1: Should I be concerned that none of the replacement kits had this metal thing under the master cylinder? What does it do (other than complicate removal!) and why is it there if the replacement kits omit this part?

2: Is the pushrod in the slave cylinder supposed to flop around like a wet noodle? Think I found my problem....

While I'm at things, I'm going to have lunch then change out the fluid in the transmission. Just going with the Penzoil Syncromesh. All the debate over the best fluid has my head spinning, so I'm just going with basic OE replacement. But I will put 6 qts in vs the 4.75 regular fill amount.

 

[GCroyle]

That is an early damper system they tried for a short time.

Powertrain engineers have a monkey on their back to always keep in check. The mayhem of NVH.

I'll bet you'd find a steel drum head damper inside to take the "vibration spikes" from the Cummins/manual trans/clutch and attenuate them keeping them from reaching the clutch pedal and your foot. From dusty memory the next time variants on these dampers were seen was on the G56 hydros and they added a flow control restriction piston thingy. Think a device that keeps you from dumping the clutch and seeing what brakes first. The whole 9 yds was on the chassis cab version with braided jacketed loom hose! I have a new one of those hanging up for a test someday, maybe.

The pushrod does flop around when removed, all's well there.

You did just fine with what you bought.