When the boom down function is activated at the end of the stroke and the pressure rises on the rod side in the boom cylinders the problem occurs, when I raise the boom it becomes very slow, I put the flotation switch on or the BSS switch it gives a blow in the hyd system and the boom up function becomes normal again. has anyone ever seen this problem , tanks for your help
Usually when guys hammer out the seals on the sequence valves. There should be 2 facing up and 2 facing down. Large caps 1⅛ iirc. Depending on vintage, you may have to remove the support bracket, some had the holes bored in them. Anyway, with all pressure removed from circuits, carefully and slowly remove those cartridges one at a time. Inspect the O-rings and back-up rings. Unfortunately, I don't believe they offer a service kit. I've always replaced them as a set. The problem arises when guys have bucket in full curl and push the boom down through it against the mechanical stops. It just destroys those valves.
Thank you for your reponce, according to me it's the # 12 for the boom down.
I can't see the whole picture. But that does look like one of them. I would remove and inspect each of them.Just make sure your boom is properly blocked up when accessing the 2 on top of the valve. It also helps to pull a vacuum on the hydraulic tank, to minimize oil loss. Good luck and keep us posted.
Yes, I'll give you news after checking. Thank you