Interesting Hydraulics Discovery Today

[DWCox]

Interesting Hydraulics Problem Discovered Today

I had bought my 2005 JD 790 this June with 33 hrs. on it. It had sat in storage by the prior owner a good portion of the time. Today it was finally warm enough to go out and warm it up sufficiently to change the trans./hydraulic fluid. I had been noticing some cavitation in the power-steering when cold, as well as a pause at the bottom of the stroke when dumping the bucket, so I was hoping this would cheer it.

I always check my fluid levels, so I was a bit shocked when only about two quarts of fluid came out upon opening both drain holes. Puzzled, I then opened up the main cap only hear a whooshing sound and see fluid pouring into my large pan (I use a portable masonry pan to catch large quantities like this all at once). I immediately pulled the breather tube only to discover that it was not breathing at all. Apparently, a mud-dobber or something had built a nest and I had never even suspected it was plugged, though this is not the first time I have seen this happen. It just didn't cross my mind.

I have since cleaned the screen (which did have some small metal shavings) and changed the filter. I have a feeling that the bucket hesitation and cavitation problems will be gone.

 

[jinman]

Re: Interesting Hydraulics Problem Discovered Today

I had been noticing some cavitation in the power-steering when cold, as well as a pause at the bottom of the stroke when dumping the bucket, so I was hoping this would cheer it.

Merry Christmas! That was a lucky find on the mud-dauber's nest. It stands to reason that if the reservoir is cold, it might be under a vacuum.

I do think that your delay at the bottom of the dump cycle might be normal. My tractor also does that and it is because of the regenerative feedback circuit. My bucket dumps quickly and then stalls, quickly followed by full hydraulic pressure pushing the bucket to full dump position. It all happens in less than 1/2 a second, but it is very pronounced.

 

[DWCox]

Re: Interesting Hydraulics Problem Discovered Today

I do think that your delay at the bottom of the dump cycle might be normal. My tractor also does that and it is because of the regenerative feedback circuit. My bucket dumps quickly and then stalls, quickly followed by full hydraulic pressure pushing the bucket to full dump position. It all happens in less than 1/2 a second, but it is very pronounced.

Merry Christmas to you as well. I got a little stir crazy in the house after presents were opened, so I went out to the garage and finished putting in the new filter and hydraulic fluid. Took it for a quick spin and all the cavitation noise is gone. Funny what a little plugged vent hose can do. I haven't worked with a full bucket yet, but it is good to know that you are experiencing the hesitation as well, in case it ongoing.