Hello everyone, I’ve got a Yanmar B50-2 making a squealing hydraulics noise. Machine is new to me, I’m the 3rd owner, previous owner had it for 15 yrs. Pretty good shape, has had a few minor issues but nothing major. Background on the machine: -New hyd fluid (iso46) and new filters -3300 hrs -There was sludge but no heavy metal on the magnetic drain plug, reservoir seemed to have minor gunk on the bottom that I wiped clean. Zero indication of water, but fluid did look on the dark side (old). -I do not have a pressure tester so have not tested any pressures. The hydraulics seem to have good power. However after warming up, I start to get a squeal coming from the control valve section when working the limits of the bucket and arm cylinders. When cold, there is no squeal, only happens after the machine warms up. Depending on how hard/long I’m working the machine it will get louder than what I posted in the video. I am including a video of it to illustrate and allow you to listen. Any input would be greatly appreciated!
If Iam seeing and hearing correctly - You are bottoming out the cylinders And opening the relief valve - that’s the squealing noise you are hearing. This would be normal for the relief valve to open when you are at the end of the cylinder travel. The relief valve has to open, otherwise you either stall the motor or blow hoses. if it’s squealing in between the ends of travel that would not be normal. However if you are moving the cylinder slowly you may hear a different noise as the valve spool is not fully open and the oil is somewhat restricted in flow.
Correct, in the video, when the arm pushes out to full extension, the relief valve can be heard with the normal noise a relief valve makes and works as it should. However, in the video when the arm comes back in and fully retracted, there is a loud audible squeal which is not a normal sound. It might be tough to hear in the video. I am suspecting maybe a bad o-ring somewhere in the control valve section is allowing fluid past, as it only starts to squeal when the hydraulic fluid warms up and becomes thinner. This sound will happen frequently when working the arm and bucket operations when the hyd fluild is heated up. There is not a squeal noise in between ends of travel. it only happens at the ends of travel or when trying to dig/lift/move something heavy that engages the relief valve. Has anybody dealt with or troubleshot anything similar to this? Just wondering where to start.
If that excavator has a variable displacement piston pump in it..most do.. those reliefs shouldn’t come into play in that situation. The pump should de-stroke before the reliefs opens.
It is a variable displacement pump. What would be preventing the pump from destroking? It only does it with the bucket and arm movements when the fluid warms up. Where should I start with troubleshooting this thing? Thanks
Cook99- I know this is an old thread, but did you ever find out where your squeal was coming from? I have an older B-50 and have been trying to track down a squeal that only happens when left track motor is lugging down. Suspect a relief valve ( I've switched them out left side and right.)which I would buy new just to check it, but Yanmar no longer has/makes them. I've also tried switching travel motors, tried switching hoses at valve manifold left for right..... problem only appears on left side. Been getting worse over several years. Not sure where to go from here, as otherwise this is a GREAT machine!! Thanks for any help!