MF 50HX S Series cavitating in hydraulics

[Jock]

G'day

Went to do a job on a MF50HX S series the other day. The drive shaft for the hydraulic pump stripped, the customer replaced the shaft and the driven gear in the pump. He also changed the oil and fitted new filters. After reassembly the hydraulics are now cavitating. The machine is jumpy and the pump is noisy. After closer inspection I found that the seal was damaged on the suction filter, hence sucking air. I replaced this and the machine worked fine

I got a call 2 days later saying it's playing up again. He has now replaced all flexible hoses on the suction side, tried running it without the filter and fitted the correct seal to the filter housing. Still no luck

Can anyone suggest anything else?

I think my last option now is to pull the pump off and make sure he has put it back together correctly when he had it apart

 

[Delmer]

Not too cold there is it? Any chance he's got water or something else contaminating the fluid? Water will make cavitating worse. Otherwise take the pump apart.

 

[Tinkerer]

Check the filter gasket again.

 

[Jock]

Just coming to the end of summer so still fairly warm. Think he's running 46 weight oil, which was changed when the pump was done.

The filter housing now has a brand new seal

I'll try and tell him his pump needs to come off again

Thanks for the replies

 

[Jock]

Customer rang me the other day, he found a suction hose that was "only replaced not long ago" that had a hole in it

When he bought his filter he had been supplied with the recommended Fleetguard filter. After talking with his supplier he found out that Donaldson produce a coarser micron filter.

So the backhoe must have been sucking air through the hole in the hose, but not leaking because of the excessive vacuum created by the wrong filter

Hence the problem is now fixed