Steering Failure

[griffon]

Bonjour from SW France,
I run a small tractor for occasional use in market gardening, on 8 acres. Last year I had a worry about the hydraulic fluid - which was clearly contaminated 'foamy', so changed it out, and all was well.
Until now in spring startup. The steering is almost impossible to handle but recovers after 20mins use. There is a whining noise which may be associated.
The hydraulic fluid marks correct level on the dipstick and appears clean. I checked this yesterday immediately after use, and today before use. The lifting arms still show capable - holding mower/rotovator.
I've already got some clues - but not sure where to start in diagnosing this problem; any advice much appreciated, thanks.
LGW

 

[dj1701]

Did you change the filter as well?

 

[griffon]

Yes ! One filter in the hi pressure circuit and one in the lo pressure feed. I subsequently had leakage with the hi pressure casing but solved that after finding a ruptured seal.

 

[griffon]

Progress ! I've got a working solution for the moment: straight after starting up, perform hydraulic priming sequence as outlined for oil change.
So, turn the wheels hard left, then right, while holding revs hi for 60s each. So it's looking fairly certainly like a trapped air problem. On closer inspection of the dipstick, the oil is a bit frothy, and higher on the stick than when I filled it ?! It seems that air pockets are forming once stationary ...

 

[rScotty]

Progress ! I've got a working solution for the moment: straight after starting up, perform hydraulic priming sequence as outlined for oil change.
So, turn the wheels hard left, then right, while holding revs hi for 60s each. So it's looking fairly certainly like a trapped air problem. On closer inspection of the dipstick, the oil is a bit frothy, and higher on the stick than when I filled it ?! It seems that air pockets are forming once stationary ...

Hydraulic fluid that has water in it becomes opaque - looks milky and foams. But if the fluid is transparent as it should be, then foaming is probably an air leak in the negative pressure - suction - line between the sump and the hydraulic pump. Hard to locate, so easiest fix is to replace the suction line and fittings. As the air leak gets worse, it will cause a rattling or whining sound in the pump and ultimately damage it.
good luck,
rScotty

 

[TractorTech]

Could also be an air leak from the 'low pressure' filter not being seated all the way.
Most modern (80s and newer) have a separate pump for steering so the 3pt lifting wouldn't be affected. 3pt holding is basically the 3pt piston holding or not.

 

[griffon]

Thanks to rScotty and TractorTech for response. I was suspecting a leak somewhere but could see no drips; a connection with suction pressure would not show itself like this, so thanks, good tip

 

[rScotty]

Thanks to rScotty and TractorTech for response. I was suspecting a leak somewhere but could see no drips; a connection with suction pressure would not show itself like this, so thanks, good tip.

Suction leaks don't show much leakage. Sometimes you can find them by looking at a suspected connection after the engine has been shut down overnight -then a suction air leak will show itself as a wetness at a joint as some of the trapped fluid works itself out. So if you have an oily hose connection on a suction line suspect a suction leak. A suction leak causes all sorts of problems but often the hole itself is physically too small to leak much fluid out - and of course when running it won't leak any fluid out at all.

I learned all this about rubber hoses on the suction side of hydraulc pumps almost by accident. The outside of the suction hose on my JD was always wet with oil at the lowest point. I tightened and re-tightened the clamps at the end, but the hose bottom and ends were always oily.

So one day I was talking to the JD mechanic and he said that is typical of old hydraulic suction hoses. The hot oil causes them to spit the longways but on the inside, not the outside of the hose. From the end, if you took the hose off and looked, the split iwould just look like a pin hole in the end of the hose. No amount of tightening with a hose clamp can close it off.

I looked at the old suction hose and he was right....I couldn't find any obvious holes. He replaced the hose and it is still dry years later.