4400 brakes

[young tractor]

Hi guys. I was just moving my 1978 jd 4400 combine and the
brakes just went to the floor and totally quit working. I haven?t
had this combine very long. Do they have a master cylinder
that could be low on brake fluid. Or is it more than likely the
master cylinder went bad. The brakes worked ok before this.
Just looking for some insight before I tear into it. I appreciate
all of your advice

 

[JD Seller]

Right behind the brake pedals on the floor, under the rubber mat< is a screw that you loosen and remove a small plate out of the floor. You can see the brake master cylinder. Just remove the cap and check the fluid.

Truthfully you more than likely blew a brake line or a wheel cylinder. Put some fluid in the master cylinder and pump the brakes then look for leaks.

 

[4520BW]

If I remember correctly they had 2 disc pads with balls in between them and never did work well. JD is right about a possible rotted line. Fill reservoir and have some pump while you look for leaks, if no one available to help tie some baler twine to pedal under cab and use it to pump the breaks.

 

[IowaJohn]

Look for leaks like JD and 4520bw say. I had a 4420 and the farthest I dared adjust the pedals were acouple of inches off the floor. Too much pedal they would get hot and stick. You will want to take the brake and spring mechanism that 4520bw is talking about apart at the wheel and check the springs, shine up the balls and rough up the disks with a wire brush or coarse sand paper to make the brakes work better.

 

[4520BW]

I had a neighbors 4420 in the shop for shoe auger bearing and they wanted brakes adjusted. I cleaned springs and scuffed pads. Had it working perfect till I got going down road and could feel it drag,I hit the clutch and it locked up the right tire and spun the combine half way around in rhe middle of the road.( had a 444 head on it) learned my lesson on adjusting them too tight.

 

[IowaJohn]

Yep! It happened to me on a muddy road. 1/2 mile from home. Didn't touch the pedals just got hot and 1 side was a little tighter. 444 ch like you, just over a hill sideways in the middle. I think if I hadn't dumped the clutch as fast as I did I'd been headed back up the hill. Thank goodness for hydros.

 

[4520BW]

Fixed brakes a 6620 hydro for a guy thought he did not need brakes till either the belt or hose broke and he went for a wild ride. I even ended up putting poly shoots on his cord head that was used to stop it. The best thing for brakes is to clean of the fodder and mud that builds up rotting the lines.

 

[andy r]

Have ran a JD 4420 for several years. I wouldn't call the brakes easy to repair on a 4400 or 4420. That being said the disks probably never actually wear out - yes they do get glazed. What happens is the brakes go bad do to inactivity. The wheel cylinders pit which can cause leakage through the cylinder AND the rubber cups in the wheel cylinders can wear or just plain get hard also letting brake fluid past. Now the same can happen to the master cylinder - pitting and bad rubber cups. You might see some wet areas/damp dust where the linkage goes into the master cylinder. I went through the lower cylinders in 2011. I think I identified brake fluid underneath at the wheel cylinder. Piston cups were hard and not pushing against the cylinder and cylinders were pitted. I pulled the individual wheel cylinders off, honed the light pitting, and installed new rubber cups. Of course the wheel cylinders are underneath where the transmission shafts come out making it a little hard to work on. John Deere sells new complete cylinders or the repair kit with the rubber cups, little metal piston, and a new spring. The part the dealership ordered was packaged wrong with larger cups so that threw me for a while. There was a note in the computer about the wrong packaging after I already tried them. Ended up getting cups from an auto parts store. The diameter of the rubber cup is molded on the back. I did not pull the disk brakes out as the brakes worked fine when the fluid was full. At that time I also did not rebuild or replace the master cylinder and never have. What I have found is you just need to check the brake fluid in the master cylinder and keep it topped off. Sometimes it will go a whole season and sometimes you might need to add some. If the master cylinder is empty fill it. Bleeding the air out - slightly loosen either the left or right brake line on top of the master cylinder and start pumping on that brake. You will see brake fluid with a lot of air. After the several pumps slowly tighten the brake lines back up especially when the brake pedal is on the compressed stroke. After a couple pumps as you are tightening you should start to get brake pedal. Maybe on the last 2 - 3 pumps, open the line slightly when pushing down, tighten the line when letting up and repeat. When the master cylinder is empty and you haven't opened up the lower lines, bleeding the master cylinder has been enough for me - gravity has always bled the lines and cylinders. Maybe there is still brake fluid in the lines? I think when I had the wheel cylinders off I did bled the lines and cylinders from below. Seems like if the piston cups and cylinders are halfway decent keeping brake fluid in the master cylinder helps keep everything soft and pliable which slows/stops the leaking. Let a combine sit for 10 months or better and a slow leak can dry everything up in the system. Sitting may allow moisture to settle at the wheel cylinders as well causing the pitting and hardening of the rubber cups. The 6620/7720 brakes are easier to work on in my opinion. I preferred to primarily to just use the brakes for stopping and not for tight turning, although my 4420 combine will spin around if the L/R brake is applied. There are a bunch of combines without functioning brakes. I do think brakes are very important for safety. Neighbor had a combine with no brakes roll backwards on gravel road - very long and steep hill. Twenty foot concrete bridge at the bottom. He almost reached the top when the engine stalled due to plugged fuel filters. It rolled backwards and he did eventually did get it cranked into the roadside ditch. The combine's next stop was Colfax Tractor Salvage. The impact compressed the back 12 feet into about 4 feet. It did have a hydrostatic transmission so they figured they didn't need brakes. Most of the ground they farm lays pretty flat. But you can see what happens when you don't have brakes.