Hot hydraulic oil in a Hi Ranger F5

[Roadking52]

Hi Folks,
Newbie here with a question about a Hi Ranger F5 bucket truck. After blowing the return pilot line off the ground control valve 3 times, I changed the nylon line to copper due to high heat softening the nylon hose and allowing it to extrude out of the compression fitting. I realize the heat is a symptom of another problem, and after feeling around the hydraulic system while unit was operating, discovered the lower boom cylinder is extremely hot, as are the hoses between the cylinder and valve manifold, and the valve manifold. All other lines are "cool". The closed center pump is cycling on indicating flow somewhere, even when the lift is not moving.

I don't think the boom is leaking down, as it is stable while extended. Oil is not leaking externally, at least only seeps. My thoughts are a leaking control valve, or a internal cylinder leak(around piston or rod seal). Anyone have any thoughts or experiences with this problem?

Thanks for any help.

Dale

 

[TRISTATEFORESTRYEQUIPMENT]

sounds like you should add a hydraulic fluid cooler with a fan

 

[VA-Sawyer]

What a useless answer ! It seems pretty clear that there is a problem that needs to be FIXED and trying to mask it by adding an oil cooler is not a fix.

From the little info from the OP, I suspect that there may be internal leakage at the pressure relief valve or the pressure switch might be sluggish and is causing the pressure relief to function on every cycle. Either one can cause fluid to heat quickly. A few checks with a pressure guage should help find the problem.
Rick

 

[Roadking52]

What a useless answer ! It seems pretty clear that there is a problem that needs to be FIXED and trying to mask it by adding an oil cooler is not a fix.

From the little info from the OP, I suspect that there may be internal leakage at the pressure relief valve or the pressure switch might be sluggish and is causing the pressure relief to function on every cycle. Either one can cause fluid to heat quickly. A few checks with a pressure guage should help find the problem.
Rick

Thanks Rick. Your ideas are certainly worth checking out. The real puzzle is why only one hydraulic circuit (main boom cylinder) is affected. Last time I used it I made sure to not extend the lower boom cylinder completely, and everything stayed cool. This is leading me to think there is an internal leak in the cylinder at the fully extended position. My thoughts are that the piston may be moving slightly on the rod, creating a small leak. Since the lower boom is over center at that point, the weight of the upper boom prevents the lower boom from leaking down. Guess I'm gonna have to open the cylinder up and take a look.

Dale