3CX 1982 White Cab hydraulic pump noise

[ErwinPWP]

Hi All,

I have a 1982 JCB 3CX White Cab (Perkins engine) since 2 years. I had to repair and fix a lot of things because the previous owners didn’t maintain the machine at all.
Nevertheless I was able to fix all the failures and problems but I still have 1 phenomenon which I cannot solve (even the root cause is not clear for me).

It’s about the sound of the main hydraulic pump when operating. The pump is a single pump type as my machine doesn’t have an extending backhoe.
When operating the machine, the pump is according to me very noisy (even at idle speed). It’s a whining and shrilling sound and when you are located at the front of the machine it drowns out the engine noise!
At 1000 revs and higher it’s a noise which sounds to me as ‘here is something not OK’. Therefore I don’t want to speed up the engine above 1000 revs. in order to avoid pump damage.

It sounds to me as pump cavitation therefore I did the following things in order to get rid of this annoying sound:

- opened the inspection hatch from the oil tank located at the gearshift stick side to check if the suction side of the pump isn’t restricted (a 3CX White Cab hasn’t a suction filter on its main pump) --> no restrictions , I was able to look thru the suction pipe into the pump
- opened the inspection hatch from the other part of the oil tank to check any obstructions --> nothing found, all pipe connections are open
- removed the sediment from both oil tank parts
- drained almost the complete hydraulic system by disconnecting hoses at various places and by opening rams (was still necessary because I had to change the seals)
- fitted a new main hydraulic filter element (and removed the sediment out of its housing)
- refilled the system with fresh and clear hydraulic oil (Q8 Haydn 32 = ISO VG 32)
- the oil level is almost at the max. mark from the tank level indicator tube
- exchanged the aluminum pump suction manifold and its O-ring as the aluminum was corroded and the O-ring was visible from outside

At the moment I’ve no more inspiration what to do more?!
Even at idle speed the hydraulics are very strong and the speed of the hydraulic movements are normal so I don’t think the pump is worn.
I’ve no idea about the running hours. The rev/hour counter is still working and indicates 2000 hours but I don’t believe this. 30 years old and only 2000 hours so I think its 12000 hours (hour counter exceeded once it’s max of 9999 hours).

I’m not able to compare it with another similar machine but if I hear the grey cab of my friend running there is definitely a huge difference in pump noise.
In Belgium you see a lot of trucks with a trailer mounted concrete mixer. Those trailers have a separate six cylinder diesel with a big hydraulic gear pump and even those machines don’t produce such an irritating noise.

Any suggestions about some more things I can do? Are here owners of White Cab’s who can tell me something more about the sound of their pump?

There is maybe one interesting item to mention which has a relation to this issue.
When lowering the backhoe dipper (so moving the dipper towards the machine) you can hear almost the same shrilling sound into the dipper ram and its hoses. This is also cavitation and it’s because of a negative load at the dipper ram.
Normally with higher pump revs this phenomenon would be less. But even with no bucket load and when moving really slow I still can here the cavitation and this is maybe not normal?


Cheers,

Erwin from Belgium

[martyn williams]

Is the Hydraulic oil of the right grade ? I have known pumps "howl" if oil is too thin , the hydraulics work fine but generates noise, pump drive problem ? or altenator /genny belt slack
Martyn

[agrimax]

46 Hyd oil would normally be recommended rather than 32 but I use whatever comes along,as long as it's clean and can't say the pump on my 82 3cx is noisy. There should be a filter on the suction side of the pump,through the right hand inspection cover,but if you have normal digging power,I doubt if damage has been done without it.Have you checked if there are any pipes/hoses rubbing against the chassis etc as that can give rise to vibration which can make a considerable noise?

[FOWLER MAN]

Hi Erwin,

You seem to have covered all that I would have checked.
There should definitely be a suction strainer in there. Though I know the strainer being missing wont cause your problem.
You say, and I agree, it sounds like cavitation and I know you have taken all the obvious steps to eliminate it.
But you dont say whether the oil actualy shows signs of foaming in use
I have had a simila problem where an auxilery pump, (like power stearing or servo), is pulling air and causing cavitation by dumping air through the return back into the main hydraulic tank.
The main pump could become noisy in 30 secconds or less after start up.
Check it out.
Fred

[ErwinPWP]

Hi all,

The previous time I had ISO VG 46 oil in it and with this oil the noise is also present. Using ISO VG 46 or ISO VG 32 oil, it’s depending on a combination of how heavy you will/are working with your machine (hydraulic oil temperature) and the outside temperature. For heavy use it's better to use the 46. But nevertheless I personally don't think that the oil is an issue. It's brand new oil and it looks clear and it has no water contamination.

I've checked yesterday some additional things. The whining noise is at its highest level around the short rubber pump suction pipe. I can 'feel' the noise when I put my hand on this tube (it's a vibrating feeling). This vibration will be transferred to the right tank walls which will also vibrate and generating some extra noise. So it’s definitely generated very near or in the pump and not by other pipes or a bad drive.
In the past I already checked the pump drive shaft and there is no play in the joints and I pressed enough grease in them.
The noise immediately starts after starting the engine. But yes it's maybe worth full to check the steering pump circuit. Good tip!

I looked also through the filler cap in the right hand tank when the machine is idling and I can see some small air bubbles which are coming out of the oil. Because of the return pipe is connected to the left hand tank I think here will be more bubbles popping up but you cannot see this because this tank has no filler hole. So I cannot say it’s foaming, only some small bubbles (which I think it’s also not OK).

In the right hand tank I found only a suction filter for the steering pump. No filter on the main pump. I’ve no service or parts manual covering my machine serial number so I don’t know if there is a suction filter on the main pump. Does anybody have a manual covering my machine (ser. no. 297758/P)?
Here is a picture of the right hand tank without the inspection cover. Don’t mind the oil quality. This was the oil when I just bought the machine, it was contaminated with water. As you can see there is no filter. If there must be a filter, how is it fixed into this hole?




Cheers,

Erwin

[martyn williams]

Is the short rubber suction pipe ok ? Had a fault on a machine that worked ok but the hydraulic pump ran hot and noisey,the cause was that the wrong rubber suction pipe was used.It was not of the strengthend type with metal coils in it.So when the machine run,the suction caused the pipe to collapse causing reduced oil flow to the pump.
Martyn

[FOWLER MAN]

Is the short rubber suction pipe ok ? Had a fault on a machine that worked ok but the hydraulic pump ran hot and noisey,the cause was that the wrong rubber suction pipe was used.It was not of the strengthend type with metal coils in it.So when the machine run,the suction caused the pipe to collapse causing reduced oil flow to the pump.
Martyn

Hi,
I've even known suction pipes to delaminate and close up internaly while the pipe still looks OK externaly.
Fred

[ErwinPWP]

Hi,

The 'free-not-by-any-metal-supported' area of the suction pipe is very short (I think about 1"). With this area I mean the distance between the end of the tank feed tube and the edge of the inlet pump manifold. See picture below (maybe it's needed to increase the brightness of the monitor as I don't have a better picture for the moment). As you can see there is some oil remaining in this free area. Because the distance of this free area is so short they didn't apply a steel reinforced tube. It looks like a rope reinforced tube.



When the pump is operating, I cannot see any deformation from the outside. There are also no damages visible from the outside.

OK this pipe is most probably the original one and thus 30 years old. Maybe I've to change it anyway. And yes maybe only the inside is collapsing during pump operation.

Another objection:
Is it possible that the pump draws some air via its drive shaft seal? The driveshaft seal isn't leaking there is only some oil sweat around the shaft. So I think the seal is still OK but you'll never know.

Cheers,
Erwin