Maintenance

[Phillyphan]

Pump makes shrieking noise when raising boom curling bucket and sometimes while moving the dipper stick. The pump was replaced about 75 hrs ago. The main relaid pressure is good and the individual line relief pressures are in spec when functioning properly but drop to 2000 psi when the noise is present. Any ideas or info would be appreiciated

[Cat_Tech]

Sounds like the main relief valve.  If it makes the noise and pressure drops, it is blowing open and staying there.  If the old pump failed, it may have debris in the relief valve and cause it to malfunction. 

[Phillyphan]

We replaced the main relief valve and followed the procedure for purging the air from the hydraulic system. The noise is still there but only after the oil warms up, when the system is cold it seems to function normally

[Cat_Tech]

That is wierd, usually the main relief will take care of that.  There are also NFC reliefs at each end of the valve body that controls the two pumps.  Possilby if one of them was sticking would cuase it.  Did you calibrate the powershift pressure when the new pump was installed, that may make a difference. 

[sroberts]

Hi there,

Have you have any resolution to this issue?

We have also experienced a similar situation.  Found that one pump would drop off in pressure to less that 500 psi, while the top one would hold at full relief pressure.  very strange.  We eliminated the system by running the pumps thru a flow tester back to tank.

Pumps were replaced and old one is going back to the rebuild shop to find out  what happened.  Just curious if you had resolved your issue?

[sroberts]

Hi there,

I have done a little more digging.  It looks like CAT has an update or service info that states there may be an issue with the suction line from the tank to the fan motor that is driven off the front timing cover.  This hose can cause a restriction and the pump will suck air in thru the front seal.  CAT also recommends to change the front seal as well on this fan pump.

This air in the system can cause some noise in your pump.  We are in the midst of making this change to try to make our pump stop whinning.

[Phillyphan · Accepted solution]

We found that the reman pump we installed was defective. We also replaced the fan drive motor hose with updated kit along with the motor front seal.

[madcash2]

Hi All,

I have been having a similar problem and its seems to have started like this... Firstly the machine had an oil leak from the seal on the inside of the pump near the coupling so the guys took of the pump changed the seal. However before this happen the operator experience some times a jerking movement in the swing as well as the stick and bucket. At this stage there was no wining noise though. Further to this the stick had a drift and would get very hard when you trying and retract it at some stage,  Anyway change the seal, filters and oil and purged the system to find a noise  from the pump as well as as bubbles in the site glass. Ok after extensive checks we found some debris in one of the valves for the stick so ordered the new seals and ready to fit we removed the stick cylinder only to find major damage to piston and bore. Next option new cylinder reflushed the system, clean valve banks machine now had normal operation but still the bubbles and whining noise. About to give up as can seem to figure out what is wrong. Sorry forgot to add removed pump and took it for testing and no problems at all. I have sis on my laptop and cat et so any tips on what to check or do next would be very helpfull.

Cheers

[madcash2]

Just replaced suction lines and seals still nothing. Discovered that the load check valve on the stick line at the valve bank has a broken sleeve!!! Let's hope this solves the problem. Can anyone tell me if that would cause aeration in the oil?