Deutz brakes

[grass man]

I have an old dx 3.90 that has developed a brake problem. If the brakes r pressed they go straight to the floor. If they r pumped up they seem to hold perfect then if released and pressed after a few seconds they go straight to the floor again. If they are disconnected the right pedal goes straight to the floor but the left works as normal. I put new seals in the master cylinders and it still has the exact same symptoms. The master cylinders r not pitted. There does not seem to b any air in the system that I can find. It does not have trailer brakes. Any ideas?

 

[Stock]

Is it leaking fluid or losing fluid internally? Is there a balancing unit on it? might be bypassing fluid internally in the balance unit...........................

 

[grass man]

No it's not losing fluid. Where is this balancing unit or what does it look like? Must be some sort of internal leak

 

[jock t]

Had the same problem with a 6.18 a few years ago. It started after we renewed the discs and callipers. Once we got it all back together couldn’t get the brakes to bleed, tried from every junction in the brake line. Next we renewed the seals in the master cylinder and it got a bit better for a wee while. Spoke to a guy who was an expert on the DX series, seems if you drain the master cylinders it’s near impossible to get them to seal again so we renewed it and it was fine from there.

 

[grass man]

You mean you put new master cylinders on it or new seals a second time?

 

[essexpete]

If there is a balancing valve that works in a similar way to the old IH type then a leak on one side will cause both brakes to fail with brakes latched. Unlatched and the good brake will work.
So as someone posted above without significant fluid loss it points to a defective master on one side.

 

[jock t]

You mean you put new master cylinders on it or new seals a second time?

I had to put new master cylinder on it, we couldn’t get the old one to reseal once we let the fluid out of it.

 

[grass man]

I'm back at this problem again. As described in 1st post the left hand brake works perfect, the right hand brake goes straight to the floor and if used together they both go straight to the floor. If I pump the right brake it comes up hard and stays hard for as long as u want. If the pedal is released for a few seconds then pressed again it goes straight to the floor. The same happens if the brakes are joined. There is a steel brake pipe between/linking both master cylinders piped into a small chamber on the bottom of the master cylinders. I don't think its air and it is not losing drake fluid. Any more suggestions? Tia

 

[jimH]

Hi

i have the same issue. Did you ever find out what the problem was in the end?

 

[Wisconsonian]

If you're not losing any fluid, then it's the internal piston seal on the master cylinder that goes to the floor. It's lost springiness. You can get it to hold from the fluid pressure, but it relaxes as soon as the pressure is released. put new seals in the master cylinder.

 

[grass man]

Ended up putting a new master cylinder on it to cure the problem. The old one seemed perfect inside but there must have been something wrong because new seals didn't cure it

 

[jimH]

Thanks for the reply.

Mine looks good too and there is no leaks.
A pipe split and leaked all the fluid out of it. i can get one side bled and the peddle is prefect but the other side wont hold a peddle. if you pump the peddle 2 times its hard and doesn't lose pressure but once you let your foot of it goes straight to the floor again.

I was convinced it was air but after a day wasted trying different methods of bleeding i will try a new cylinder.

 

[jimH]

I installed a new master cylinder but still have the same issue. I have spent hours trying to bleed it but there doesn't seem to be anymore air in it. Has anyone another suggestion?

 

[Zetor]

I installed a new master cylinder but still have the same issue. I have spent hours trying to bleed it but there doesn't seem to be anymore air in it. Has anyone another suggestion?

Check your slave cylinders, if they are partially/fully seized can cause the same symptoms

 

[jimH]

Thanks for the reply. I should have said my deutz is a dx85 and I don't think it has slave cylinders. Maybe the newer DX's did

 

[Wisconsonian]

Where do the brake lines go then??? and where have you been trying to bleed the air?

Usually you only have to bleed at the slave cylinder, on a typical car. Tractors, with dual brakes, are somewhat trickier, follow the procedure as there are usually several bleeders to use in sequence.

 

[jimH]

I have been bleeding them at the calipers which is the only place to bleed them. The deutz brakes are a bit different than a typical tractor. There is brake shoes but they are only of a handbrake and aren't hydraulic.
There is 2 calipers on each side and a master cylinder serving each set. I had a mechanic over for 4 hours yesterday and we tried everything we could think with no luck.

 

[Wisconsonian]

the caliper is the slave cylinder, fair enough. I would still want to find the procedure for bleeding those brakes, and follow that. Not saying it's impossible that something else is wrong, but if brakes worked until the pipe leaked, and then the brakes stopped working, I'd suspect it's still air.

 

[laich]

Did you try, filling an oil can , with brake fluid and pumping it in through the bleed nipple , back up to the reservoir ? I have had to for this before on DX's

 

[box]

A couple of thoughts:
-If the tractor has the wrong caliper fitted (i.e. a LH caliper fitted on both sides), the bleed nipple may be on the bottom and it would be impossible to bleed with the caliper mounted (depends on the caliper)
-If the caliper has a hard seal on one of the pistons, it may be holding the piston in place instead of allowing the piston to slide along the cylinder and take up any clearance between the pad and the rotor, causing the symptom you're describing.

You can rule out a caliper problem by clamping off the rubber hose going to it (if you're lucky enough to have a rubber hose going to it). If not, you can remove the line and cap the end off.

As @laich said, reverse bleeding can help to purge any remaining air out. You can also use a syringe.

Make sure your master cylinder pushrods are adjusted correctly.