544G Brake pressure light warning.

[crewchief497]

We picked up a new loader here to move snow with and i have been fixing all the little issues that we were not told about when we bought it. One of them is after you run the machine for a few minutes every time you hit the brake pedal you get a brake pressure warning light. It works fine when rpms are up and brakes are not touched, but as soon as brake pedal is depressed, low brake pressure indicator comes on, and the loader transmission kicks out, and won't engage until you raise rpms. Brake pressure indicator doesn't have to go out before it moves, but it seems to be a low pressure issue. The machine has pretty high hours. Is there a pump that powers only the transmission or is it a sign of excess leakage somewhere in the system? I have a service manual but no where in the manual does it talk about hooking up and checking brake pressure with a gauge. Thanks in advance!

 

[Nige]

Does it have a nitrogen accumulator in the brake system.? If so the precharge pressure would be the first thing I'd suggest checking. You'd need tooling that connects to what I assume would be a valve of a Schrader or similar type on top of the accumulator.

Another quick check would be to blank the brake lines to either the front axle or the rear and see if the problem continues, then switch the blanks to the other axle and see what happens. With the brakes being wet you could have a failed brake piston seal on one or more corners.

 

[Diesel Dave]

There is an accumulator in the brake system. It’s teed in the brake circuit supplying the (2) brake valve inlet ports.
Brake accumulator nitrogen pre- charge spec is 500-535 psi.
I would agree with Nige to check the accumulator pre-charge first.

 

[Diesel Dave]

FYI ,The brake pump is bolted to the back face of the loader hydraulic pump. The brake pump is fed hydraulic system oil and the pump supplies oil for the park brake at full pressure 2300-2400 psi. The brake pump also supplies the brake circuit ,pilot circuit, and (differential lock circuit if equipped) at reduced pressure 550-650 psi.

 

[heymccall]

To test accumulator, run engine at high idle for 30 seconds.
Shut off engine.
Turn key on.
Depress brake pedal several times, until brake pressure light comes on.
Should be a minimum of 3 applications before warning lamp.

As for brake pistons, check oil level in both axles. You'll need a 1-1/4 tool to loosen and remove fill plug. Each axle has one dipstick and one dummy plug.

If an axle is overfull, then a brake piston in that axle is suspect.

 

[Diesel Dave]

If the machine is equipped with front and possibly also rear hydraulic differential lock, by design the axles overfill somewhat.
I think Nige’s suggestion (quoted below) would work best to check for brake piston leakage.
“ Another quick check would be to blank the brake lines to either the front axle orthe rear and see if the problem continues, then switch the blanks to the otheraxle and see what happens. With the brakes being wet you could have a failedbrake piston seal on one or more corners “

 

[crewchief497]

Well thanks everyone that fixed the issue. I wasnt able to recharge the old accumilator due to the new design and it had no port to check it. I picked up a new one and installed it and its working great!

 

[James S Coad]

Could you by chance take a picture and send it to me.
I'm in the dark here

 

[James S Coad]

Accumulator