890.3 not moving

[Thinnnber]

I was moving my New to me Valmet 890.3 8wd up a Forest service road hill when it decided to not wanna go up and applied the brakes. Just 20 feet behind me there was a side road and I force the machine down the road and off. It was chattering and having a hard time moving but because it was down hill it got there barely. Once it got to the flat it will not move anymore. It seems like the working brakes won't release or something. When switching from forward to reverse you can see it tries to move the tires a few millimetres but it is stuck where it sits Any help would be much appreciated.

[Thinnnber]

This Machine has sat for 10 years and ten years ago it had basically the same issue I'm having today.IMG_3947.jpeg

[Ljohnsaw]

Wow, almost $10k for a hydraulic motor!

[Thinnnber]

Yes sir and that was in 2015.

At this point I'm gonna head out tomorrow and pressure test the same as in the repair bill. Time to see if now I have to buy a hydro pump or motor.

[Thinnnber]

So ive had so little time with this machine I don't know what feels right But.....when the park brake is on the brake pedal is full of pressure. when I release the park brake the pedal falls to the floor and has no feed back. when I throttle up in gear the pedal gets feed back but when I release the throttle it falls down again. from the little time ive spent in this machine it seems like that's not correct? anyone Have any ideas?

[leeroyjd]

Have you tried calling a Komatsu dealer? I've had good luck with Roland Machinery's service over the phone, although my machine, a 646 is much simpler.

[Thinnnber]

Just got back from pressure testing the 890.3 pump tested good then when following the manual for the motor I got zero pressure forward or backward at 1500 RPM. pressure is suppose to be 45MPa so that's no good. Called Komatsu and they wanna send a mechanic to test it before I order a motor. Motor was replaced already ten years an ago and only has 50 hrs on it. pump price $20,000 not including removal and install. ugghhhh

[fluidpowerpro]

Just a reminder that pressure is relative to load so if the motor was spinning freely.with no load, the pressure will be low.

[barbender]

So, you arent getting any pressure to the circuit that supplies the brake release it sounds like?

I only know my way around Ponsse forwarders, and that's as an operator, not a mechanic😊 
There are valves on the brake circuit called "Nautilus Valves", I think that is the brand name. Im not exactly sure how they operate other than they modulate the pressure to the brake circuit. You can hear them cycle, kinda like a pressure switch on your home water system. Which I think is what they are basically doing, whenever the brake circuit pressure drops enough, you'll hear the valve hum/vibrate. 

Sorry I'm not more help.

[chep]

Yeah before throwing 20k at a pump I'd track down someone who really knows the machine. Last summer on our rottne we had the "linkage" go the hyd pump, it was a brass sleeve that houses the connection.  But, no movement. Pump tested good, and el3ctric signals to the pump were fine. Had to pull the pump in place and put a new sleeve in. Cheap and easy just time. Start simple

[leeroyjd]

Could it be charge pump or hydraulic accumulator?

[Thinnnber]

So...Hydrostatic pump needs 3.0MPa pressure at idle we have zero. When we give it full RPM and go into forward and reverse it will spike to 3.0MPa then fall to zero (machine trys to move). So we hooked direct pressure to the pump, once the machine starts it wants to take off but because the Park brake is activated it stalls out. So we know the motor works and the pump works. What we think is the pressure reducing solenoid isn't opening fully, its getting signal as we tested that but it looks like its only opening a fraction of what it should. This Pressure reducing Solenoid supplies the pump with 3.0MPa which we are missing. So I have ordered a couple but they look like they are a few weeks out.

[barbender]

Thanks for the update, hopefully that does it for ya