Finally addressed the forever lousy 460 hydraulic system performance today. Installed a rebuilt Cessna pump.I was very concerned about the pump's intake system. Despite installing a new pump and putting to rest questions about pump output, I felt for sure there would be a problem with cavitation due to old O-rings inside the transmission and such. Once I finally got the 460 to start (hasn't run since August) after installing the pump, it ran for about 5 seconds and then a horrible low-pitch squealing noise was heard. The 460 bogged down, and I immediately shut it off. My first thoughts were that the pump drive got destroyed, but looking down at the fast-hitch I noticed it had raised up fairly high. Well, apparently the pump picked up prime and was moving oil which was a quantum leap over the totally shot (and I do mean TOTALLY) old pump. It had been so long since the drawbar was able to be raised that high, I figured the lift cylinder had topped out and the pump was up against the relief valve causing the nasty noise. I then positioned the lever so that the hitch would be lowering when I started the 460 again. I started her again,and the hitch began moving downward with no noise until the cylinder bottomed out, making more noise with the tractor bogging down. I raised the hitch--no noise until topping out. Well, you get the picture. I have to continually cycle the hitch up and down to avoid the noise and bogging the tractor. There is no "neutral" or hold position--the hitch must be kept moving. If I try to "hold" at a certain height, the noise returns. The noise sounds like a relief valve blowing off although it is a much lower note than other high-pitched reliefs I've been around. It's like a very fast--frequency chatter. The 460's system never was 'right' all the time Dad had it. Most of the complaints were water in the system and lack of holding position. It's been eons since the 460's system has seen the pressures the newly installed pump seems to be delivering. Sorry for the long ramble. Any suggestions?
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