M929 Hydraulic Pump Very Noisy

[Russ Knight]

I need a little help troubleshooting the hydraulic system on my newly acquired dump truck. I have many years of experience operating machinery that uses hydraulic pumps, but have never wrenched on them much. The pump is cavitating, very noisy, and the bed is very jumpy when raising it. The hydraulic reservoir is 2-3 gallons low, but I wouldn't think it is low enough to cause this much trouble, but maybe so. I'm hesitant to top it off because if this isn't the problem then I'll have dump the fluid which due to the hydraulic tank not having a drain (that I can see), will make a big mess. It appears there is some kind of cannister (filter inside?) on the pump return line to the tank. Is it a filter? Any tips or suggestions would be greatly appreciated.

 

[87cr250r]

If it's jumpy there is air in the system. You'll need to run the cylinder through several full strokes to clear it out.

The normal amount of noise is characteristic of the pump. Gear pumps are the noisiest, vane pumps are the quietest.

 

[Mullaney]

I need a little help troubleshooting the hydraulic system on my newly acquired dump truck. I have many years of experience operating machinery that uses hydraulic pumps, but have never wrenched on them much. The pump is cavitating, very noisy, and the bed is very jumpy when raising it. The hydraulic reservoir is 2-3 gallons low, but I wouldn't think it is low enough to cause this much trouble, but maybe so. I'm hesitant to top it off because if this isn't the problem then I'll have dump the fluid which due to the hydraulic tank not having a drain (that I can see), will make a big mess. It appears there is some kind of cannister (filter inside?) on the pump return line to the tank. Is it a filter? Any tips or suggestions would be greatly appreciated.

.
Other than @87cr250r 's suggestion about air in the system - is it possible that the suction hose side of the hydraulic system has cracks in it - from the tank to the pump - where it might be drawing air? Or maybe that the suction line might be collapsing? Maybe laying under the truck in a safe spot and actuating the pump, then the handle to control the bed and see if it's something goofy rather than expensive...

 

[Valley Rock]

If your hyd res is 3 gallons low with bed down, that's certainly where I'd start, then if problem continues address filters .

 

[porkysplace]

2-3 gallons low is not good , the cannister is most likely the normal place for them is the return line . I would also check for leaks in the feed line to the pump {low pressure side} if it sucks air it will cause the issue you are describing .

 

[Russ Knight]

If your hyd res is 3 gallons low with bed down, that's certainly where I'd start, then if problem continues address filters .

The only possible filter I see is on the return line from the pump to the reservoir.

 

[Russ Knight]

.
Other than @87cr250r 's suggestion about air in the system - is it possible that the suction hose side of the hydraulic system has cracks in it - from the tank to the pump - where it might be drawing air? Or maybe that the suction line might be collapsing? Maybe laying under the truck in a safe spot and actuating the pump, then the handle to control the bed and see if it's something goofy rather than expensive...

I thought of that (suction line collapsing). My sone is home this weekend so he can help me. Everything looks tight, no evidence of any seeping leaks or otherwise.

 

[Russ Knight]

2-3 gallons low is not good , the cannister is most likely the normal place for them is the return line . I would also check for leaks in the feed line to the pump {low pressure side} if it sucks air it will cause the issue you are describing .

I guess I'll take a chance and go ahead and fill the tank.

 

[porkysplace]

I guess I'll take a chance and go ahead and fill the tank.

Probably should change the filter as well .

 

[Russ Knight]

Probably should change the filter as well .

Where is it located? Is it that small cannister with the hex head on the bottom of the canister?

 

[porkysplace]

Where is it located? Is it that small cannister with the hex head on the bottom of the canister?

It should be in the low pressure feed line , It might help if you post pictures .

 

[Russ Knight]

No filter on the suction line.

 

[Jbulach]

Where is it located? Is it that small cannister with the hex head on the bottom of the canister?

I believe it’s the same as m925. Vane pump that is not supposed to be run at over 1800 engine rpm and gets very angry sounding if you go above that. The filter is in the return line up inside the passenger frame rail. After setting to allow any water to separate, drain a little off the bottom of the tank to check for water, change the filter and inspect for debris, then top off the oil. Unlike the m925, I think your m929 should have a tank vent, make sure this is not plugged.Can’t remember who to search but someone else on here had the same problem a few years ago and iirc it was due to running fluid low and sucking air.

 

[Russ Knight]

The addition of hydraulic fluid corrected the issue.

 

[Russ Knight]

I believe it’s the same as m925. Vane pump that is not supposed to be run at over 1800 engine rpm and gets very angry sounding if you go above that. The filter is in the return line up inside the passenger frame rail. After setting to allow any water to separate, drain a little off the bottom of the tank to check for water, change the filter and inspect for debris, then top off the oil. Unlike the m925, I think your m929 should have a tank vent, make sure this is not plugged.View attachment 896145Can’t remember who to search but someone else on here had the same problem a few years ago and iirc it was due to running fluid low and sucking air.

Thank you for the information. It will be super helpful for future maintenance. Mine is exactly as pictured.

 

[Gatorbait2.0]

Oil and filters go a long way, saves you money in long run. The hyd tank fill should have dipstick for correct level, and it does have a filter in that canister. If you don't know when it was changed last replace it. Old hoses can also be a problem,rubber doesn't last forever.