What kind of assembly lube do you use when assembling a hydraulic pump and hydraulic cyclinders
hydraullic oil. The key point IMHO is not what assembly lube you use, but how you handle the startup of the pump or how you exercise the cylinder(s) in question. That will have far more influence on the long-term reliability of the component you rebuilt.
Ok any advice on that part? I ask about the lube because I’ve been watching videos of professional pumps shops and they use some kind of thick lube on all the parts. I was thinking about just using Vaseline on the parts along with filling the pump with hydraulic oil
They do that because that pump may sit for months. They have no way of knowing when that pump, valve or motor might be put in service. If you are rebuilding for you, you know it's not gonna sit. Always lube with what it lives in. If I'm building an engine, I build with Rotella 15w40. If I'm doing an axle, its wet brake or gear oil, whichever is called for. Save the petroleum jelly for o-ring and seals. As Nige mentioned proper handling and cleanliness are key as well as proper start up. Eliminate the risk of cavitation and dieseling, you're 99% ahead of the game.
This...............and the comments regarding keeping everything spotlessly clean.
I second what ever it lives in as above. Hook a hose to the test port of pump and crank machine over with engine disabled from starting until you get a good flow of hyd oil after you get it installed.
I've always assembled components with whatever fluid is supposed to be in it.
I use trans assembly goo for cylinder assembly, o-rings, seals usually. Hydro pumps get pre-lubed with the weight AW fluid they are going to be running.
Working in the Caterpillar spec shop, we used Lithium complex NLGI 2 for hydraulic piston and head assembly lube and kept a weed sprayer with clean 10w hyd oil for lubing cylinders. The sprayer would reach all the way down the bore.
I second what is stated above. The big thing with pumps is to find a way to force oil into them before you start them turning. You are trying to clear as much air out of them as possible before you turn them on. On systems with the pumps way above the reservoir, I fill the pump up with oil before hooking up the discharge connections. On excavators, there is usually a case drain or a bleed connection somewhere on the pump. I'll open those up and put some air pressure on the tank to force oil into the pump. You will hear any air as it clears through the pump. It will hammer like it has rocks in it.