Hydraulic question. At work we got a machine to be specific it is our problem child, it is a FUCHS 350 magnet crane. It has more hydraulic problems than you can shake a stick at. Fix one leak and get to more the next day and so on. Since we have had this machine in 3 rears we have replaced with out a doubt 50 hoses and or fittings and a few spool valves. So the questions I have is. One of main boom cylinders leak and both will bleed down really bad when the machine is cold. Once it is hot it will bleed off but real slow. Will this symptom cause or let air in to the hydraulic system? And will it cause the machine to make to much pump pressure because air is getting in the system and not letting the pressure relief valves work properly? Causing us to have so many leaky hoses and fittings? It is so bad this machine can use up to 30 gallons of hydraulic oil a week.
A leaking cylinder should not let air in at all.If your pump runs low on oil it will cavitate and fill the system with air,but your machine will not work anyway.If your cylinders are leaking down it could be the cylinders or most likely your holding valve bleeding by. You need to get a set of gauges and check all your pressure ports. This will narrow down your problem
Could be a cavitation issue creating a "water hammer" effect on the hose and spool valves shortning their life. Has this machine ever had a pump or major system component failure on the hydraulic system?
sounds like your over heating your fluid to me. No advice on the cure but your in the perfect storm to overheat your hyd fluid.
Humm worked on hydraulic systems for years and taught hydraulics for Ga Tech and Adult Ed so may have a few ideas. As for leaks, leaking hoses I do not understand. Hoses with swaged fittings are the best way to go. Never liked the screw on/together fittings. If leaks are in maybe a hydraulic manifold, where the directional valves are located, problem could be high temp causing the "O" rings to "cook". High temp fluid will harden the "O" rings like french fries and they will not conform to the area where they seal. Using better quality "O" rings, (cost a bit more) will prevent them cooking hard. Also be sure the right size rings are used. I've had machines run for weeks 24/7 with no leaks but when they were shut down maybe over a weekend they would leak like crazy when restarted. Replacing all the o rings fixed until next time. Problem would have not been there if there were proper oil coolers installed. Use liquid teflon on all hose threads etc. DO NOT USE TEFLON TAPE as even a small tiny piece can shut down a hydraulic system. Seems some folks do not apply the tape properly and it breaks off a small bit and SHAZAM system shut down. The liquid will prevent this problem. Some cylinders will leak or drip when the system is shut down because without any pressure some of the rod seals will not seal or relax so to speak. They normally won't leak while the system is running. Cylinder rods usually have maybe a couple of seals and the wiper seals to keep dirt/grit out and away from the pressure seals. Oh yes, always buy the best quality "O" rings and NEVER USE THOSE kits where you cut the rubber tubing stuff and glue it together to try to make an O ring. You probably know what I'm talking about. Those homemade O rings are crap and destined to pull the friggin GLUE loose. I have no idea where that idea came from but they are pure CRAP. Hope that might help a bit.