How should a new hydraulic pump sound?

Inno · May 21, 2012

I recently replaced the original front mounted hydraulic pump on my MF 202. The old pump (a Cessna gear pump) was beyond worn out.
The new pump, also a gear pump makes a whining noise when turning. Is this normal or is there something I should be checking out?
I'm guessing this may be normal for a new gear pump.

JDseller · May 21, 2012

A hydraulic pump should not be making any noise you could hear over the engine noise. Does it have a built in relief valve?? If it does then you may need to set the out put pressure up if it is bypassing all of the time. Also your system might have a problem that was not just the old hydraulic pump.

Check and see if anything is getting warm to the touch just setting there running. If there are any hot spots then there is a high pressure internal leak there.

I assume that it is an open center system. Check and see if the return lines/tank are not restricted. Make sure all the control valves are returning to center. I have seen valves that have broken internal springs just return half way and block the oil flow just a little.

If that all checks out then it could just be how it is going to sound but I would check things out first. You don't want to ruin your new pump. There could have been something else wrong that made the old pump fail sooner.

mkirsch · May 21, 2012

did you prime the pump? are the hydraulics working?

Goose · May 21, 2012

Could be the gears need to run a bit to get polished and used to each other.

New square cut gears in a quick change rear end on a stock car would whine for a few laps until the surfaces got polished and "broken in".

Then again, it could be a defective gear. I'd run it for a bit and see if it quiets down.

Inno · May 21, 2012

Yes all the hydraulics are working and working very well. I do not believe there is a relief valve internally. I did not prime the pump as such but once I hooked up the suction line and filled the tank I assumed (perhaps incorrectly) that it would flood the pump and any air would work itself of the system. The system gets warm to the touch all over, as it did with the old pump, I also assumed (perhaps incorrectly) that this was just as the fluid gets pumped through the system it got warmed up due to friction. Nothing is too hot to touch though.
It is an open center system and the loader controls are all working correctly (new 2 years ago). There is nothing about the operation that makes me believe anything is wrong but the sound is not what I am used to hearing. I upgraded the return lines as someone had previously used adapters and brought it down to 3/4", now it is all 1" all the way through. I may have to check any relief valve on the loader controls.

730d se · May 21, 2012

It should not be louder than the engine. Old fluid, new gears, relief not set will cause it.
The relief valve being set properly is critical. It will either perform poorly on the low side or break things if it is too high.
The neat function of fluid is that it will not compress, so it has to go somewhere when it is not being used to push a ram piston.

Paul Janke · May 21, 2012

You didn't ask at all, but do you have a filter in the return line? Not having one will drastictly reduce the life of the new pump. Also, you mentioned having increased the size of the return lines. Even more important is to have a large suction line which runs from the reservoir to the pump.

Inno · May 21, 2012

According to the literature on my loader control valve the relief pressure is factory set at 2000 psi and is adjustable from 1500 to 3000 psi. I guess I will have to get a pressure gauge and do some adjusting.

Inno · May 21, 2012

(quoted from post at 10:54:05 05/21/12) You didn't ask at all, but do you have a filter in the return line? Not having one will drastictly reduce the life of the new pump. Also, you mentioned having increased the size of the return lines. Even more important is to have a large suction line which runs from the reservoir to the pump.

Yes, there is a filter on the return/suction line just before the pump intake. Although now I'm thinking maybe it can not provide enough flow fir the pump as it is the orig. filter canister. And what I meant was the suction line, not the return line. I increased all the fittings on the suction line from the reservoir.

jfharper · May 21, 2012

Inno,
One idea is you could take the filter out temporarily and run it for a short time to see if the whining goes away...this would answer your flow idea...but don't run for too long b/c you may be pulling dirt into the new pump. I remember asking the dealer one time when I should change my filter and they said every 250 hours, and a total fluid change every 500 hours...I wonder if your documentation says anything about that.

Another idea is to call surplus center and tell them...maybe convince them to send you a replacement on their dime since this maybe a manufacture defect...one you may want to handle now rather than later...then if the replacement whines then probably the issue lies with your system rather than the pump.

John B. · May 21, 2012

After reading everyones' post you may have a collapsed suction line internally that you can't see. Causing cavitation in the pump which can ruin your new pump.

Anonymous-0 · May 21, 2012

Filters on the suction side are a BIG NO,NO!. You need your filter on the return line. If you have anything on the suction side it should be a 100 mesh strainer

Inno · May 21, 2012

Thank you for that info. I only did it that way because that's how it was done originally. I will get a proper filter and put it on the return line. Makes sense now that I think about it.
10 micron filter?

Just thinking about how it's set up. It won't be too hard to add a filter to the return line from the loader and PS but the backhoe dumps right into the reservoir too so I'll have to add a filter........or do some more plumbing for that too.

Heat Houser · May 21, 2012

Hmm...my IH560 has a filter on the suction side with a bypass. It was designed that way by IH engineers.

Inno · May 21, 2012

Maybe it was ok with the old pump but not with the new one.........I dunno. The old one lasted 50+ years with the filter before the suction port.

Inno · May 21, 2012

Another question, why when I look at filters on the surplus center website do I see some listed as return filters and and some as suction filters?

RodinNS · May 22, 2012

Check the suctions screen/filters. Whine is often associated with cavitation which is also associated with pumps that are 'beyond worn out'.
There could also be a leak somewhere on the suction and it's drawing air...

Rod

Inno · May 22, 2012

I am planning to replace the suction line and put a filter on the return lines and remove the filter at the suction port of the pump.

RodinNS · May 22, 2012

I don't know if removing the suction filter is such a great idea... but certainly making sure it's clean and of an adequate size is a good start.
Also remember that you need a larger diameter rubber line than you do steel line because rubber has considerably higher friction loss for the same size ID.
I would tend to think that if you've got a 15-20 gpm pump then you'd want a 1.5" plus ID steel line. Longer line and lines with a lot of bends suffer more friction loss. You can always adapt it down at the pump to fit but the line and tank port should be on the larger size...
Nothing wrong with adding a return filter either but given a choice I'd prefer the suction filter.

Rod

36 Coupe · May 23, 2012

You should hear the pump whine on my tractor on a cold morning.Hydraulic wood splitters whine on a hard split.

David G · May 23, 2012

I am not a fan of filters on Suction line, and believe they should go
on the return line.

Whining is usually an indication of cavitation, and cavitation can
ruin a pump. Did you change anything but the pump? Is the GPM
of the new pump different?

How should a new hydraulic pump sound?

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