Bleeding a master and slave cylinder

[Welder Dave]

I'm hoping to get the master cylinder for my 730A back this week. I need to bleed it at the slave cylinder and it doesn't have a traditional bleeder you can put a hose on. It just has a screw that fits in a seat. The problem is the slave cylinder is at about the same height as the master cylinder. The shop doing the master said I could gravity bleed it taking the bleeder screw out and holding the clutch pedal down. Then close the screw and let the clutch pedal up and then wait 20 seconds for any air to come up and then repeat. Will pumping the clutch pedal a couple times force the brake fluid to the slave cylinder? I'm thinking I might have to hold or somehow clamp the master at a higher level to bleed the system and then install the master. Anyone have experience with bleeding a horizontal brake line with little to no drop?

 

[Tinkerer]

'Anyone have experience with bleeding a horizontal brake line with little to no drop?

I haven't with a horizontal line.
But I have had a little experience with a brake bleeder pressure tank.
It would be perfect for your situation.

 

[Blue-Fox]

I'll agree about the pressure bleeder. Makes things much easier.
Dave, You'll need to bench bleed that master before you put it in the machine, which just basically involves getting a stub of tubing about 5-6" long and screwing it into the output port and looping it back into the top, putting fluid in there and pumping it until you get a solid stream of fluid. Then I just tape over the top so you don't get any crap in the top and install the M/C unit. Now swap out the hose for the tube still screwed in the body port, so you only lose a minimal amount of fluid. You can pump the pedal several strokes and then hold it down just like a car brake, and crack that bleed screw. If you just take the screw out with everything static it may bleed out, but not likely to evac the trapped air like using pressure does.

 

[Welder Dave]

The other issue is the hyd. booster is bolted to the master cylinder. It's a fairly heavy unit and not a lot of room to get it mounted under the cab. I'm curious if the threaded filler cap on the master is a standard size thread. If it is maybe I could improvise a pressure bleeder using a giant syringe.

 

[Welder Dave]

Finally found out the master cylinder is too pitted to be repaired. Shop is going to see if they might have something or can get something for less than what an OEM M/C would cost. He said it might have a different style of cap but as long it works I'm OK with that. He also said it looks like someone might have put regular oil in it. The internal cup seal was more swollen than the end one. Jade wants $800 for a new master cylinder less the booster. Hopefully the slave cylinder is still good.

 

[cuttin edge]

And that's the worst part. It's not like it's an unusual master. But they want an arm and a leg for it. Sky hook, and raise the front of the machine up higher than the rear. I remember a fella with an old GM gas job with a trailing axle and hydraulic brakes. Whoever built the rear axle, put the brake shoes top and bottom like air brakes, with the wheel cylinders mounted up and down. Only way to bleed them was to use the overhead crane at the GM dealer. Clel would sit in, and they would pull the front bumper to the ceiling, he would pump, and Reg would crack the bleeder. I'm sure the safety man would love it.

 

[1693TA]

I've had to do that to several vehicles in the past. Quick and easy if you have either a bridge, or gantry available. Wheel lift on a tow truck works well also.

 

[Welder Dave]

The brake shop finally got everything fixed. It kind of sucks it took so long considering that had a new master and a kit for the booster in stock. New master was only about $25 cheaper than going through Jade Equipment. I wonder if that could have something to do with me saying Jade wanted close to $800?? The guy did say Mico is pretty expensive.

I hope my MX track is busy on the weekend. The new M/C, rebuilt booster and fabricated 60" brake hose comes to about $1550.00 with tax. I wanted to fix it right so hopefully I never have to deal with it again. I'm praying the slave cylinder is good. Parts are so ridiculously expensive in Canada. A new M/C in the US is $364.00. The problem with ordering one online is it may not be set up for a clutch (no check valve used) and what if there's a problem with it.

 

[Welder Dave]

I got lucky and a guy at my MX track helped me put the new master cylinder and rebuilt booster back on the grader. Wasn't really that hard to bleed and the clutch slave cylinder seems to be working although I couldn't fully test drive the grader. It seems from sitting for a month or so it leaked enough hyd. oil I couldn't raise the moldboard. Seems a little odd it would leak that much with the reservoir under the rad. but stranger things have happened. I had plastic caps on all the lines. Maybe that wasn't enough. I picked up a pail of hyd. oil. I hope I don't need to buy multiple pails of oil. Oil was $93.00. I might find some cheaper but not by very much. It makes you appreciate the minor $100 repairs more but unfortunately the simpler repairs are rarer.