check the seals by all means but if this is a fluid displacement cylinder then there are no seals on the ram, they are all in the packing nut on top of the cylinder shell where the ram comes out.
You are going to have to remove the cap/packing nut anyway to get access to the inside of the freelift cylinder so once you do this remove the ram and look in the base of it and check the safety flow valve. Make sure it is there and intact, if it is not then it may have come apart and is laying down in the bottom of the cylinder in smashed up pieces.

I have see quite a few of these do the exact thing you speak of and pretty much always it was that safety valve causing a misstaging problem. Usually caused by the snap ring failing that holds the valve in.

Its called mis staging. Freelift cylinder may have bad inner seal

it's indeed strange

Hi, it has to have it. I did not remove it....and some time works just fine, than in next 20 min wont work.....strange.....

Hey Tantadruj, just an idea can you control if the free lift cylinder has got a down safety valve sometimes it's inside the cylinder or on the outside nipple.
Reagrds
Marcb

Thanks Adams1
I'm also thinking about air in cylinders....
Can you give me a part number of pressure valve? Are you thinking about line brake safety valve? Can you show me on the picture....

check for a pressure valve going to the primary lift cylinder. sounds like its weak and sending oil to the secondaries as well

It's not good! the same problem.....I don't know what else to do?
The main hose is original, oil 32, rollers are good, mast is clean....
Only appears when fast lift.....

Tantadruj, thanks for your reply.
Regards
Marcb

Problem solved. I changed oil (repsol 32) and now works just fine..... I'll also try with Repsol 46....

Thanks for all suggestions.

Check if the lift cylinder is in the right place maybe you remove both
cylinder and when you return it it was swoop. If this will happen this
problem will occur.

Best regards,

Rolly

Hello Tantadruj; we've experienced that when the diameter is to small the oil flow isn't correct.
Don't know exactly what it must be, we had that problem whit a Komatsu.
I'm not saying that hose diameter is your problem it is just an idea and we experienced that in the past.
I'll hope you can solve your problem.
Kind regards
Marcb

Thanks for help.
I will change oil.....
I don't know about hose, will ask.....what size has to be? If it's bigger can be problem, to much oil at the time....

I ones head the same problem. The oil was to thick.
I changed the oil to Valvoline HVLP 32.
and there where no problem after.

Hey Tantadruj, has somebody changed a hose of the free lift cilinder? we had the same problem in de past, somebody changed the hose but the inside diameter was wrong so at high speed it lifted the 2 outside cilinders as well.
Regards
marcb