MF270 Brakes (I'm stuck)

Guys, I'm looking for a little help to complete some work I'm doing on my brakes.

I had a master cylinder sticking on the right side. I took it off and got it all cleaned up and working smooth again. I've got it back on the tractor and spent a couple hours tonight trying to get the lines bled, however, I can't seem to get it bled out.

I am having my son pump the pedal. I open the bleed screw and have him press, tightning the bleed screw before he lets up on the peddle. When I open the screw prior to pressing the peddle again, it sucks air back in so I'm not getting anywhere. I took the line off the pilot cylinder (the one going to the master cylinder) and put my finger over the port in the cylinder, when the peddle is released, it produces suction which is why I'm not getting anywhere, it's hauling back as much air as what is expelled each cycle.

What am I missing? Is the pilot cylinder working right?

Thanks guys, I'm stuck for now.

Jamie

I've never bled brakes that way. Have the pedal pumped up several times, then held down. THEN turn loose the bleed screw, pedal should go down, then tighten the bleed screw. Repeat until the pedal feels normal. Another way if you are by yourself is to use a vacuum bleed hand pump to pull the fluid out the bleed screw after making sure the master cylinder is full.

Maybe your master is not stroking back far enough to allow more fluid past the piston when the pedal is released.

Hey Dieseltech, I appreciate your reply. I switched to what your are telling me to do. I am getting the same results. It seems that the fluid isn't getting pulled past the pilot cylinder. The line between the pilot cylinder remains full of air. I am trying to rig up something so that I can vacuum the oil in as you suggested. Not sure how much suction I need.... I'll post what I come up with and results.

Thanks again.

Jamie

Hello,
I have attached the page from the MF 600 series manual on the bleeding procedure. This may not be exactly the same
but will be very similar. However there are a number of things that should be checked in addition to this. First of
all from experience when a master piston seizes through lack of use or starts to leak they are normally beyond
recovery even with a new seal kit. Corrosion and pitting in the bore can render them useless or give only a short
time when resealed. If you are sure that the bore is in good condition have you assembled the components correctly?
If you have not resealed the cylinder is there any damage/wear on the sealing edges? Is the line from the reservoir
to the m/cyl clear? Follow the pipe down to the slave cylinder and ensure that there are no kinks or crushes in the
pipe. Are you able to pump fluid through normally? Have you repaired the slave cylinders? If these have been
disturbed the slave cyls MUST be fitted with the bleed screw above the pipe from the m/c or you will have air trapped
inside. You should have attached a piece of pipe to the bleed screw. Ensure that the lower end of the pipe is ALWAYS
kept below the level of the fluid in your drain reservoir.
If you are sure that all of the above is correct then bleed the system as per the MF instructions. Ensure that the
bleed screw is fully open. Ensure that the m/c is full of fluid. Now the interesting bit-- Slam the pedal with your
foot to push it to the floor as quickly as you can. Before you release the pedal close the bleed screw. As you
release the pedal you should see the reservoir level drop. Do this several times until you are sure that there is no
fluid containing air passing into the drain container. Make sure that the reservoir is kept full at all times. If you
still have no pressure check whether the brake rod on the actuator is being applied. It may be necessary to tighten
the nut to create pressure in the circuit. If the nut is tightened to the point that the wheel locks and you still
have no pedal pressure then it looks like a seal problem in the m/c.
Let us know how you get on.

Hey guys, thanks for your help so far.... here's where I'm at.

I removed all the lines and blew compressed air through them to make sure everything clear. I then put everything back together, opened the bleed screw on the master cylinder of the side giving me trouble and blew air clear through from the reservoir out through the screw (just 5 lbs to verify continuity). I then removed the pilot cylinder and filled it with oil. There isn't a bleed screw on the pilot cylinders of my tractor but I filled the cylinder on my bench and the line from the reservoir is the high point when its mounted, so I'm reasonable certain I have the cylinder full. My reservoir is mounted high on a fender so I was then able to let the line from the reservoir to the pilot cylinder fill by gravity and connect the fitting with the oil dribbling. In my mind this should ensure that I have air free system up to the pilot cylinder.

I made a gadget for my shop vac and tried to vacuum oil through to the secondary side of the circuit. No luck, it just didn't work. Perhaps not enough suction...

We tried pumping the brake pedal 10 to 12 times and then opening the bleed screw. The first time it burps a little air.... after that nothing. I was expecting the oil to come though to the secondary side of the circuit, however, the reservoir level doesn't change at all. No oil is getting past the pilot cylinder to the master cylinder side of the circuit.

I am going back out to try a couple of the things in DavidP post.

Jamie

I am away from home for work, sorry for the late post. I struggled with this and got nowhere. The only thing I have left to try is to move the pilot cylinder from the left side to the right to prove out if the pilot cylinder is working properly. I am still not getting any fluid past the pilot cylinder.

I am back home on the weekend. I'll post my progress.

Thanks,

Jamie

OK, I got it! First of all, I am using the wrong language. There are twp cylinders on my tractor. One on the peddle, one on the back axle. I have been referring to the one on the peddle as the pilot cylinder. My local dealership straightened me out.... this is the master cylinder.

I took the master cylinder apart again and actually figured out the issue. There are two rubbers that essentially act as a check valve allowing oil to get past the master cylinder into the line going to the main cylinder on the back axle. The two rubbers separate under the power of a little spring between the two. The rubbers were sticking together with a little crud between the two and the spring was a little weak. I stretched the spring out a little and cleaned up the rubber pieces, put it all back together and was able to bleed it using some of the information posted earlier.

Thanks,

Jamie

(quoted from post at 23:22:50 01/02/16) Guys, I'm looking for a little help to complete some work I'm doing on my brakes.

I had a master cylinder sticking on the right side. I took it off and got it all cleaned up and working smooth again. I've got it back on the tractor and spent a couple hours tonight trying to get the lines bled, however, I can't seem to get it bled out.

I am having my son pump the pedal. I open the bleed screw and have him press, tightning the bleed screw before he lets up on the peddle. When I open the screw prior to pressing the peddle again, it sucks air back in so I'm not getting anywhere. I took the line off the pilot cylinder (the one going to the master cylinder) and put my finger over the port in the cylinder, when the peddle is released, it produces suction which is why I'm not getting anywhere, it's hauling back as much air as what is expelled each cycle.

What am I missing? Is the pilot cylinder working right?

Thanks guys, I'm stuck for now.

Jamie

Click to expand...

Just for the record, I have 1984 270 Ferguson. When replacing one of the brake master cylnders (one left - one right) and bleeding them, open the little brake line on the master cylinder, the one toward the back. The hardest one to get to. I just push the pedal for that master cylinder all the way down. hold it down and tighten the fitting back up. Repeat until you have brake fluid running out and you have a good pedal.Just make sure the reservoir is full.