I have problem with hydraulics system on O&K RH 8.5, machine work well and pressures are good, but suddenly machine start to be too slow and pressures drop to around 200 bar, after I shut it down and start again it work well some time. But after problem back again and I need to shut down and start it again. Problem is probably with electric can someone help me to solve it ? Regards, Milos
Check the pilot pressure
It looks like electric problem, because when I shut down machine and start it again all is good some time. Is there proportional power valve on O&K RH8.5 ?
Hello, I have a problem with the O&k8.5 in operation, it suddenly loses power and when I reduce the gas to a minimum and increase it again, everything is fine! Can you help?
Lose power of engine or ?
The hydraulics lose power
Some problem with electricity, there is proportional valve that regulate displacement of hydraulic pump
Do you know where that valve is located?
One hose from hydraulic pump follow and you will find... near engine
Thanks
The proportional valve is normally located behind the cab. Its in a block with several magnetic valves and an accumulator. The proportional valve is the one that is adjusteble from the underside. You measure the pressure from the proportional valve at the main pump at the measure nippel in the middle on the pump. I think you have a rpm related problem. It can be the engine losing rpm because lack of power or the rpm-sensor giving wrong value. This will cause the PMS system to regulate the pumps to achive the correct rated speed (rpm). If this is the case you will see this if you measure the pressure from the proportional valve. Pressure at idle 45 bar. Pressure when working in ECO somewhere around 20 bar( i dont have the exact value fot RH 8.5, only for RH 8). If the pressure in ECO rises when you lose hydraulic power it is because the PMS system regulates the pumps to avoid overload of engine.
Hello, where could the problem be in the electronics?
Unit that control proportional valve is problem
I have a similar problem on the O&K MH CITY excavator, I bought another used PMS but nothing has changed. Did you manage to solve the problem?
I can't solve the problem either.
And how to solve the problem if it grows
To solve the problem you have to find it first. On O&K with powerproblem I always start with measuring the proposional pressure because it will tell you a lot of what is going on. I also suggest you change the instrumentcluster to rpm readings to se if you get any strange rpm readings when you lose power. If you get strange rpm readings when you lose power that maybee explains why it works ok if you turn the accelerator nob to low idle and then back to high idle again. If the rpm readings are to low the proposional pressure will rise and the hydraulic pump will turn to Qmin and you lose power.
To make it eaysier for you to find your problem I will try in short to explain the O&K PMS system. I can only explain PMS3 system because I have never repaired any Dash5, but I have once plugged in the O&K EDS TESTER which is O&K s diagnostic computer to an O&K 6.5 to see if there where any major difference between PMS3 and Dash 5 and as far as I remember there where no big difference but this was more than 20 years ago so I cant be sure. O&K RH8 PMS3 Deutz engine, auto idle disengaged, eco mode: 1. At low idle the PMS computer sends 800mA current to the proportional valve. Result: Full pilot pressure of 45 bar from the proportional valve and lowest possible torque in the hydraulic pump, low idle mode. 2.When the acceleration knob is turned to full throttle the PMS computer will send somewhere around 500mA to the acceleration motor. Result: High idle. At this stage the PMS computer will measure the rpm and calculate the rated speed of the engine whitch is depending on emission stage of the engine somewhere around 95% of the high idle. The PMS computer will NEVER allow the engine rpm to go below rated speed and will decrease the pump torque to maintain the rated speed of the engine. That's the reason to check the rpm in the instrument cluster/dashboard because if the rpm readings fails or disappears the PMS computer will probably send the hydraulic pump back to low Idle setting of 800mA. 3. When the joysticks are moved pilot pressure will go to the spools in the main valve but also to a bank of shuttle valves under the cabin floor and activate a pressure sensor in the end of the shuttle valves. The signal from the pressure sensor goes to the PMS computer. The PMS computer will change the current to the proportional valve from 800mA to 430mA. The proportional valve will change the proportional pressure from 45bar to 19bar. Result: ECO mode torque setting of the hydraulic pump. If the shuttle valves fail the hydraulic pump will probably go back to idle mode. If the pressure sensor (or sensors I don't remember if it's one or two) fails the hydraulic pump will go back to idle mode. The wire between the sensor and the PMS computer could also be your problem. When you turn the acceleration knob to low idle and back to high idle the above described process starts again from the beginning. I would check the function of the above described first because to me the function of your proportional valve and The PMS computer seems correct but you have a communication problem between your sensors and your PMS computer.
Pozdrav. Imam isti problem na bageru. Da li si uspeo da popravis svoj bager?
Need to post in English as per forum rules.
This is a great explanation. I would love to be able to read explanations like this for pretty much all systems, it really helps to understand what is going on and from there, get some idea of logical steps. Cheers
The speed sensor was faulty
The speed sensor was faulty
Where is the sensor located?
the sensor is located on the coupling between the pump and the motor
In what position is that sensor located?
Correct, thats where its located on Deutz engines. Early 8.5 is equipped with Cummins engine and later 8.5 with Iveco engine. I is basically the same engine, but not exactly. I once owned a MH City with Iveco engine and the rpm sensor was located on the top of the flywheel cover instead of the side.
I'm from Serbia too. Could you send me your contact, I can't fix the excavator
062226086