CAT 930 HYDRAULIC WHINING NOISE 41k06100

[crut47]

I have an old Cat 930 in my shop that has come in for its annual service for a customer and there has been a complaint of a whining noise on this machine when the boom/bucket is in use.

We have serviced this machine for over three years now and have not had many issues with it. The complaint is that when the boom or bucket function is engaged the hydraulics whine. I have verified the complaint and it is quite pronounced. The functions do not need to be over relief to begin whining and will whine almost immediately if the engine is at higher rpms when running them. We have removed and cut open the hydraulic filter and there was not any contamination to speak of inside of the filter pleats.

We installed a new hydraulic pump and still no improvement to the whining noise. It has a third function but it is not in use and the handle has been cut off at the base. Any suggestions would be much appreciated as to where to focus our search.

 

[Nige]

Fancy posting a Serial Number so that people can look up technical informaiton.?

 

[crut47]

Fancy posting a Serial Number so that people can look up technical informaiton.?

Its in the title of the original post?

 

[8V71]

Noisy hydraulic system common issues, Air entering suction either hose or oring on tubing or restriction in suction. Does the oil look foamy or signs of air.

 

[Nige]

Noisy hydraulic system common issues, Air entering suction either hose or oring on tubing or restriction in suction. Does the oil look foamy or signs of air.

Especially when it’s a vane pump.

Inside of the hydraulic tank checked for anything possibly blocking the suction outlet.?

 

[crut47]

Oil does not appear foamy and the suction tubing is new from the tank bottom into the elbow onto the new pump. the orings at tank and pump are new. I do not think its an air intrusion issue on the suction side but I have not checked inside the tank for restriction at the oil suction pipe/tube

 

[OzDozer]

Have any new pipe/hose elbows been fitted in the system lately? Any kind of flow alteration in this bend area is likely to cause whining. Poor machining, ridges left inside the fitting, this is where I'd be looking.
Can you use a stethoscope/screwdriver to ear, to try and pinpoint the exact source area of the whine?

I owned a 41K series 930 many years ago, it was a very good little loader and never gave me any real problems, apart from brakes when working in muddy conditions.