bleeding brakes

keith

Sr. Member
Joined
Dec 21, 2007
Messages
176
Likes
0
Points
16
#1
I am working on heavy duty equiptment with a brake system I am not framilar with. This system is a hydrolic brake system with an upper and lower wheel cylinder. The only bleeder screw is on the lower wheel cylinder in the upper port. If I bleed the brakes here will at the air come out of the upper wheel cylinder. Or is there a specail way to bleed brakes like this. The two wheel cylinder have a small brake line that connects them, I think it goes from the upper w/c lower port to the lower w/c lower port.
 

Tony

wrench
Joined
Nov 13, 2006
Messages
1,619
Likes
2
Points
38
Location
Oregon Coast
#2
Sounds like a Lucas system.
Should be bleeders or bleeder ports on both wheel cylinders, as they generally are the same part number. Just that one may have a plug and the other a bleeder.

Did someone work on this before, cause the bleeders should be on the highest wheel cylinder.
 

keith

Sr. Member
Joined
Dec 21, 2007
Messages
176
Likes
0
Points
16
#3
Ok let me clear up this. The wheel cylinders are the same. The upper has two port one line in and one line out to the bottom wheel cylinder. So both ports are used by lines no bleeder here. The lower has a line in the bottom port from the upper w/c and a bleeder in the upper port. But I agree the bleeder should be in the upper which is why I was asking?
 

Tony

wrench
Joined
Nov 13, 2006
Messages
1,619
Likes
2
Points
38
Location
Oregon Coast
#4
What kind of equipment is this on?
Kind of sounds like an old loader or maybe an old Chevy C30 truck?
If we know what it is on, we may be able to find more info on it.

The upper cylinder, does it have the line to the lower cylinder on the upper port of it? If it does, the old C30s had that type of set up and the only way to bleed it was a pressure bleeder that could push the air out of the upper cylinder, thru the line on the upper port, into the lower cylinder, where it would come out the bleeder screw on the upper port of the lower cylinder. If I said that right, it may make sense. :ROFL

They are a bear to bleed.
 

keith

Sr. Member
Joined
Dec 21, 2007
Messages
176
Likes
0
Points
16
#5
This is on an old Galion 15 ton crane model 150A. I think you are starting to see the problem here with how the brake lines are ran. Exept you have two lines a little crosses but mostly right. I am sure it will in fact be a bear to bleed even more do to the fact the master cylinder is under the drivers seat able only to get to through a small whole my hand cannot even go through.

Ok the brake lines again come down the axle, hard steel line- to a rubber hose at the wheel then to a short hard steel line- into the upper port (where a normal bleeder would be) of the upper wheel cylinder. Then still upper wheel cylinder out the bottom port and into the bottom port of the lower wheel cylinder. At the lower wheel cylinder there is a bleeder screw in the upper port.

I have never used a pressure bleeder because I have never had to, my question is also how to get the air out of the upper wheel cylinder unless I can remove the backing plate (which I did already) and twist it on the rubber hose 1/2 a turn and to bleed a and reinstall. (if I did this I would switch the bottom wheel cylinder ports and put the bleeder at the very bottom so upside down would be at the top???? Does this sound like a possible option? Or can I some how bleed this at the lines- I just dont have faith that that would remove all the air maybe most but probably not all.

Thanks for the help.
 

keith

Sr. Member
Joined
Dec 21, 2007
Messages
176
Likes
0
Points
16
#6
Just looked again I have the lines crossed not you Tony. It does go in the bottom and out the top of the upper wheel cylinder.
 
Joined
Nov 14, 2006
Messages
1,226
Likes
0
Points
36
Age
118
Location
enderby british columbia canada
#7
if there is room to move under there i would try to reroute the lines.main line to bottom cyl.then out the other port on bottom cyl to upper cyl.then put the bleeder into the other port on upper cyl.problably have to bend up a couple of lines which is why i asked about space.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
6,009
Likes
60
Points
48
#8
Re-plumbing was going to be my suggestion, too. Even if you have to use hoses where hard-lines could be used, you will still probably end up with better brakes than that crazy arrangement that is there.
 

Tony

wrench
Joined
Nov 13, 2006
Messages
1,619
Likes
2
Points
38
Location
Oregon Coast
#9
Without images, it is hard to explain.
But, the design is set up to push air out the top cylinder top port, into the bottom cylinder and out the bottom cylinder top port, under a FLOW.

Pumping the brakes will not provide enough flow to push all of the air out the top cylinder into the bottom. Only pressure bleeding will provide that.

It is a messed up system and GM, Champion, Galleon, FMC and a few other manufacturers used them a lot in the 70s. There are even some old motorhomes that may still be on the road with those systems. They were a nightmare then and pose even bigger problems today, as very few people are familiar with them anymore.

The problem with re-routing the hose/lines, is that you would have to route the hose to the bottom port on the bottom cylinder, then move the steel line to go from the top port on the bottom cylinder to the bottom port on the top cylinder and put the bleeder on the top cylinder top port. AND once that is done, you have to worry about something catching the hose and ripping it off.

Remember, if you alter the engineered design of a commercial vehicle and something happens, they will be looking for the person who altered it.
It's best to try and work with the current design and get it bled the best you can.

I've only had success with using a pressure bleeder on these systems. I have NEVER been able to get the bleed by pumping the brake pedal.
I hope the best for you.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
6,009
Likes
60
Points
48
#10
Tony, I hadn't considered the liability issues of modifying the brakes, even if you did a perfect job with all hard-lines, and all tucked in "better than new". I am withdrawing my suggestion to re-plumb.
 

keith

Sr. Member
Joined
Dec 21, 2007
Messages
176
Likes
0
Points
16
#11
Thanks for all the input. I did infact choose to re- plumb the lines for a few reasons. First I do not have a pressure bleeder. Second, the master cylinder is under the cab and you have to remove the seat and reach through a small hole to fill it. For obvious reasons the designer of this decided this was a bad I idea. So when I ordered the new one it came with a remote brake fluid reservior. As I remember power bleeders attach to the caps of the master cylinder or reservoir (in this case). However in all my years (which is not to many) I have never seen a cap like this, which leads me to believe a pressure bleeder would not work to well (this cap is big like a 1990's Toyota Camry but screws down with threads not a radiator cap style). However, I am sure I could have came up with a way to do it with an air blower in the hose to the remote reservoir anyway. But I wanted to think long term, (if I ever have to work on this again). The way it was if you blew a 12 inch rubber brake hose it would be a two and a half day job to fix it with trucking and bleeding. Now it is a six hour job. That is because you have to remove the tires and they each weight 1000 lbs. Anyway I most finished it today, should be bleeding it tomorrow. I am waiting for a backing plate to come UPS in the morning at the price of over $1000 for just one. The master cylinder and reservior was $475.

I also thank you for the concern over changing the brakes. I did consider this. I am very by the book normally when it come to repairs, but since they have been using this for the last year with no brakes at all anything would be better than that. Also the machine goes maybe for 5 or 10 mph so... well ... also then need to use in 2 day... and I ran the lines very nice almost looks original minus the rust. Well I will let you know how it works.
 
Joined
Feb 5, 2008
Messages
184
Likes
0
Points
16
Age
118
Location
north western N.J. sussex co.
#12
I have worked on that type syst. you can bleed them without a powerbleeder , a pressure bleeder makes it easier. now air goes to the high point , so brake fluid goes in to bottom of upper cyl. > brake fluid comes out of top of upper cyl. it goes through the jumper line to the bottom of the bottom cyl and you bleed air out through bleeder in top of bottom cyl. .. brake fluid will drip through because M/C is at the high point. DO NOT PUMP THE BRAKE PEDAL LIKE AMATURES DO !!!! all you do is move air back and forth. Pump pedal ONCE and hold , open bleeder, close bleeder , let up pedal and pump once again, ect. ect. ect. that way you keep pushing the air out. I hope this helps. I tell my helper " Down " they push the pedal down and they say down so I know it is down and when I say " UP " they let the pedal up and they say up ,, saves a lot of confusion on where the pedal is so you do hot have to start from the begining. als check the M/C sometimes there is a bleeder on the outlet portthat you have to bleed first. Good Luck
 

keith

Sr. Member
Joined
Dec 21, 2007
Messages
176
Likes
0
Points
16
#14
I wanted to thank everyone for the input on this. I did replumb the lines then bleed the brakes. Brake bleed easy in about 15 minutes with to people. Now I have a nice high firm brake pedel. Thanks