Hydraulic Noise

[TomBolton]

I have a '63 Cub that I'm just getting started on. I'm getting a good bit of hydraulic pump noise. It seems to come and go, but is mostly there. It's a classic pump noise, but varies in intensity. It's louder when working against the orifice in up mode, as you'd expect. Other than the noise the hydraulics work perfectly.

I have read the related links and have flushed the system and bled for air. The fluid is usually clear, without the tiny bubbles you'd expect with air noise. Occasionaly it will look milky. Sometimes all I have to do is open the filler and the noise is completely gone. So my guess is I have a bad shaft seal on the pump and am getting air in the fluid, but could it just be a worn pump??

I hate having the noise because the motor sounds so sweet otherwise.

Thanks for any suggestions.

[Harold R]

Tom, usually a bad seal on the pump shaft allows hydraulic fluid into the engine crankcase. You'd notice when you check the oil. Out of the 3 tractors I have, none sound the same. Some are just noisier than others. However, not sure how you would keep getting air in the system and no fluid leaking out.

[TomBolton]

Thanks, that gives me something to think about . . . . I'd just assumed that the running pump would suck in air. But you're right, most of what I read talks about getting hy-tran into the crankcase. That isn't happening. It did sit for years, I think I'll just keep working the hydraulics and flushing it.

[Harold R]

Don't know how much you're willing to tear into it, but there is a filter screen in the block. I replaced the one in my '50 cub and it quieted it some. It does require tearing the block portion down. Which leads to "might as well do the whole thing". If it isn't leaking any fluid, and is working well, I'd be tempted to just change out the fluid and let it ride.

[TomBolton]

Iv'e been looking at that filter in the manual. I wasn't sure how involved it is to get at it, but you have cleared that up for me. I'm thinking of running a mix of tranny fluid and penetrating oil for a bit, without any load, and see if that helps. The way it will sometimes run perfectly quiet makes me think it can be improved. Thank you.

[Jim Becker]

Don't put anything in the hydraulic system other than high quality hydraulic oil. Anything else is asking for trouble. If you think it needs flushing out, put in fresh hydraulic oil, run it a while and change it again.

[TomBolton]

Thanks Jim. Just talked to another owner of several Cubs who said that hydraulic whine isn't unusual with Cubs. Sure wouldn't want to buy a new pump after seing what they sell for!

I'll flush it a few more times. Thanks to all for your comments!