Today I was testing a komatsu PC300-7. When you raise the boom or use the arm out or in and also when traveling or trying to steer, you have a noise coming from pump. It is not a whinning noise, it is a sharp noise. I checked the suction strainer and it is clean. I checked the hyd. oil and didn't find contamination. The relief at low idle is 160bar and the relief at high idle is 360bar. With 360bar I don't think that the pump is damaged. Could it be the servo piston that make this noise?
Did u pull the pressure screens at top of pump?
Do you mean the inline filter? No I didn't. By the way when I am testing the pressure, I test before the filter and at the same time I read the pressure on the monitor and they are the same, that's why I didn't check these filters.
Any chance the noise is coming from the pump drive gearbox?
Does the pump drive have any type of "cushion" coupling in it ..? The type of noise you are describing (without actually hearing it) sounds like the noise a 245 used to make when the rubber blocks in the coupling were starting to fall apart. There was an inspection cover on the bottom of the housing which, if you pulled it off and a pile of rubber bits fell into your eye, you knew you were in for a coupling replacement.
Well, on this machine there is a damper disc (only metal) without rubber
Komatsu runs a damper disk that looks like a clutch disk. It is two plates with springs in mating slots like a dampened clutch. There is no rubber in this unit. I have seen the springs loose tension and fall out but that was in very high hour Dash 3 machines. Drain the oil out of the damper case and see if it is black, burned smelling and over full. I am thinking that the relief pressure should be the same at low idle as it is at high idle. Did you set the swing brake when checking the pressure? The pump will only supply enough oil to go over relief when the two stage or power shift pressure is activated. Otherwise it will only put out enough oil to beat load sense by about 300 PSI. That might not be enough flow to oversupply all the normal seepages in the valve bank. Have you lost performance in any single function or all of them that coincides with the noise? Maybe run some cycle times and check against the book. You might also try using a stethoscope on the pump to make sure that is where the noise is coming from. Is your hydraulic oil getting hot?
I didn't set the swing brake when relief. I loast performance in all function and in particular on load, and as load increase the sound increase. Also hydraulic oil is getting hot, even more than 80 degree C (176F)
How many hours on this machine? It is beginning to sound like a tear down and inspection might be needed. A flow meter test would probably confirm a problem but not a lot of people have one close at hand.
it has 12000hours. I removed the pump and it is in good condition. Except cavitation inside cylinder (barrel) almost at half length. I do not think that cavitation will justify the difference in pressure between low idle and high idle. Maybe this cavitation is making this noise but I am not sure about it.
What do you mean by cavitation? What I have seen in the past that was attributed to cavitation is what look like worm holes in the piston bores. Could you feel the marks with your finger if you rubbed over them? If so the barrel assembly is ruined and that is likely your noise source.
If there is no rubber in the coupling then maybe have a look in the coupling housing for bits of broken spring from the damper. A "tired" damper would probably produce all sorts of weird noises when the pumps were heavily loaded.
Pumps nfg
The weird thing is the differene in presure between low idle and high idle and the high hydraulic temperature. Because I already tested other machine, and the relief pressure at LI and HI was the same 355bar for work equipment. Anyway, I think the difference in pressure is related to the high temperature. This should be a frequent problem on these machine because it is not the first machine having this same behavior. Anybody had this behavior before?
Low pressure at idle, coupled with high oil temperature usually means a serious internal leak or oil bypassing at pressure. Just because you can get rated pressure at high idle with zero flow doesn't mean the machine can actually do any work when you need flow and pressure simultaneously. You need to hire someone with a proper flow meter to check if the pumps will provide rated flow and pressure. If not, rebuild, if so then diagnose other hydraulic system components, relief valves, spools, etc. 12,000 is usually the outer limits for the pumps on these Japanese excavators in my limited experience.
piston and shoe.
there is no play between piston and shoe