Tractor hydraulic pump whine noise??

[namesray]

Just noticed a slight whining noise coming from the hydraulic pump on my Kubota b7800 at days first cold start. The noise can't be heard at idle, but you can start to hear it after bumping up the throttle a bit and gets a little louder the higher the rpms. While I am moving the loader functions, the noise stops. When I stop moving the loader, the noise is back. It seems to go away once the fluid warms up after about 5 minutes or so. Loader and hydrostat transmission seems to work fine throughout. I did just change both the hydraulic and hydrostat filters. NAPA/WIX filters and Kubota super udt2 fluid. I know the filters are cross referenced right. The noise is just slight and hydraulics are still working fine. What could be the cause of this noise so I can possibly narrow this issue down or maybe its nothing to be too worried about??? Tractor has 1600 hours on it.

 

[jwareing]

I would bet it's just cool hydraulic fluid flowing past the relief valve. When a function is selected, oil flows though that circuit instead of past the relief then when the function stalls, the relief should bypass again. Normal closed center system operation.

 

[Leejohn]

I would say it's the hydraulic filter you put on from napa. I would get a kubota filter for the hydraulics. Take a shop vac put in the fill hole and you well not lose much sudt oil when you change it. What was the napa filter they gave you?

 

[namesray]

I think the system on the b7800 is open center hydraulics.

I too am leaning towards the filter, but why? The filter they gave me was wix 557089 (napa 7089 equivalent) I am 99.9% sure it is crossed referenced correct. Just for info the hst filter is napa 1361.

Kubota filter # hh670-37710 (hyd)= napa 7089

Kubota filter # hh660-36060 (hst)= napa 1361

wix makes napa filters=usually drop the first wix number and that is the napa equivalent.
even if it turns out to be the filter, could some one tell me what would be different between Kubota and napa/wix filters? wix filters are a good filter company and I have seen many of their filters on many different equipment with no problems caused. Why would this Kubota tractor be so fussy?

 

[SSdoxie]

Cooler oil flowing through the lines and across the pump create a vibration/whine. When some pressure is applied by moving the loader, the pressure pushes against the pump and lines stopping the vibration.
A different hydraulic filter might help it. The Wix filter might be just a bit more efficient making it more difficult to move the oil through it when oil viscosity is heavier.

 

[namesray]

Cooler oil flowing through the lines and across the pump create a vibration/whine. When some pressure is applied by moving the loader, the pressure pushes against the pump and lines stopping the vibration.
A different hydraulic filter might help it. The Wix filter might be just a bit more efficient making it more difficult to move the oil through it when oil viscosity is heavier.

This is what I was leaning towards, but I am still unsure.

Here is what some further testing/thinking has put me.

I did the old plastic handle screw driver/stethoscope trick to hear better and more directly if it was the pump and it sure is. The screw driver to the ear on the pump made the noise much louder and easier to hear and when I did the same trick on other near by engine areas, the sound did not amplify there, only on the pump itself, so I am pretty sure it is the pump making this noise.

As for if it is the colder oil or the hyd system losing prime, there are 2 reasons I feel this noise it temperature related and not the sys losing prime. # 1 the loader responds normally immediately at start up and all functions work while it is making the noise, and it takes atleast 5 minutes for the noise to stop and all hydraulics work throughout. Reason #2 today it was much colder at first start and it took atleast 10 minutes for the noise to stop. So I feel the noise is aided by colder hyd oil and as stated before, the noise seems to go away completely once warmed up.

I also learned today that the noise also goes away while I am raising the 3 pint hitch. not lowering, but I think it is gravity down and not pressure down. The loader also still has the same lift capacity through out as I lifted logs tonight with it, both while the noise was still there and after it quit making noise.

While it was making the noise I grabbed the suction line in various places to see if the whine or hum in the pump quit and it did not.

So I am still wondering why this noise is there and exactly what the noise is. I know the filter could be the culprit and I do have Kubota filters to try, but I would like to know if this noise is harmful=(cavitation) or just a noise that doesn't mean much. I know certain hydraulic systems/pumps do make a hum/whine noise when the temps get colder and they do just fine and last a long time.

If nothing else, please help me understand hydraulic systems and filters a little more. thanks again.

 

[namesray]

Cooler oil flowing through the lines and across the pump create a vibration/whine. When some pressure is applied by moving the loader, the pressure pushes against the pump and lines stopping the vibration.
A different hydraulic filter might help it. The Wix filter might be just a bit more efficient making it more difficult to move the oil through it when oil viscosity is heavier.

If this is the reason, would this be harmful at all?

 

[Texasmark]

Well how about the oil you used? Cold weather spells viscosity change and if the new oil has a higher viscosity at the colder temperatures, the pump could be sucking on it but it's not moving as fast as the pump would like so it creates a minute vacuum on the suction side which causes bubbles and the bubbles are what's making the noise.

Once the fluid warms viscosity drops, flow increases and the bubbles disappear. Or, as stated, it's a pressure relief valve jabbering at you and the thicker fluid causes it to over/under compensate, the lag causing the pressure differential and the noise. I'll bet on it being the pump especially since you heard it making the racket.

Tractor mfgrs make tractors, not fluids, tires, gens, fan belts, batteries, on and on. They either generate a spec and find someone to build what they want under their badge, or shop the market for something available that suits their design requirements and may go to them for a paint/badge modification.

Wix is one of the largest, if not the largest ww filter mfgr. and serve some of the most demanding applications besides being the mfgr. for numerous after market parts suppliers. Usually the first two letters specify the seller, and the last 3 identify the specs. So you can get the same filter with different paint from half a dozen suppliers if the last 3 numbers match. Going to bet you that in no way will they cut you short on a spec with their reputation. They have a very functional cross ref chart on the www and also show the specs for their filters.

My 2c on the subject.
Mark

 

[Navasot]

Your thinking to much about this... Cooler weather will do this. Let your tractor warm up a bit before you start using it during the winter

 

[namesray]

Well how about the oil you used? Cold weather spells viscosity change and if the new oil has a higher viscosity at the colder temperatures, the pump could be sucking on it but it's not moving as fast as the pump would like so it creates a minute vacuum on the suction side which causes bubbles and the bubbles are what's making the noise.

Once the fluid warms viscosity drops, flow increases and the bubbles disappear. Or, as stated, it's a pressure relief valve jabbering at you and the thicker fluid causes it to over/under compensate, the lag causing the pressure differential and the noise. I'll bet on it being the pump especially since you heard it making the racket.

Tractor mfgrs make tractors, not fluids, tires, gens, fan belts, batteries, on and on. They either generate a spec and find someone to build what they want under their badge, or shop the market for something available that suits their design requirements and may go to them for a paint/badge modification.

Wix is one of the largest, if not the largest ww filter mfgr. and serve some of the most demanding applications besides being the mfgr. for numerous after market parts suppliers. Usually the first two letters specify the seller, and the last 3 identify the specs. So you can get the same filter with different paint from half a dozen suppliers if the last 3 numbers match. Going to bet you that in no way will they cut you short on a spec with their reputation. They have a very functional cross ref chart on the www and also show the specs for their filters.

My 2c on the subject.
Mark

Good read here, thanks. The oil I used is what is recommended and the same I have always used. The bolded print above mentioned is what I feel the noise is, caused in some way by the filter, but are those bubbles harmful to the pump?