I am testing TVC valve output of a komatsu PC300-3. I measured 22bar at low idle and 25 bar at high idle (joysticks and travel levers at neutral). I have changed those small strainer filters and seals of servos (NC CO TVC servo linkage). Tested also pilot pressure and it gives 30bar at low idle and 40bar at high idle which is normal. By the way at low idle and high idle main pump pressure front and rear are beween 22bar and 26bar. In other words TVC output should be almost 25bar. Is it a weird or normal behavior? On these particular machine TVC current of the solenoid is constant, doesn't change with speed (old model machine)
Workshop manual may be it help you https://drive.google.com/file/d/1pi1nDpz5fScmjDdC1iHv5XH-EZl-o6Zf/view?usp=drive_link
I would think that output in neutral is normal with either the 2 stage olss or 3 stage olss type systems. Note 3 stage olss systems TVC are variable controlled with a prolix bypass whereas 2 stage olss systems are on/off with current limit resistor, refer to pages 326 to 341 of the workshop manual. Best regards
It doesn't have a hose on the CO and on the relief valve. It is a single stage relief.
Yes, it appears that by way of serial number breaks only certain machines had the option of CO port and the shuttle for the 2 stage relief. See diagrams attached Best regards
I have noticed that engine RPM on this model is 1700 high idle, while on other PC300-3 it runs at 2100RPM high idle. even TVC pressure of this model as seen in the manual is different: 23bar at neutral and 16bar at one pump relief