Post By starbolin
OT -- Flushing a Hydraulic System
I was given an old zero-turn lawnmower with a blown engine. I already have a replacement engine so that is no problem, but the hydraulic fluid (supposed to be 15W50 Mobil 1) has water in it. I am going to take the hydraulic system apart to thoroughly clean it out Ė what do I use as a flushing solution, especially for the pumps and motors?
Thanks in advance.
What's the hydraulic system pressure? I assume for a mower it's pretty low. For a low pressure system you could flush with almost any solvent, kerosene, diesel, mineral oil; although I would probably just flush with more hydraulic fluid.
Starbolin -- As best as I can tell, the contunuous working pressure is 1,000 PSI. Would you consider that high or low?
1000 PSI is enough to be considered high pressure. Get a leak in it and wave your hand in front of the leak and lose some flesh.
If you are disassembling the hydraulic system, any cleaner you want to use is adequate. You are "disassembling", not flushing. Clean, reassemble, refill, and go to work.
Is it really Mobil1 that they specify? I find that odd, that they would call for an oil sub that was about 5 bucks a quart back then. A DTE would probably be a better and cheaper source.
ATF would PROBABLY work, but I don't know the rubbers they used in that unit.
My 3 year old Simplicity 0 turn wants Mobil 1 in the hyd.s,I thought it strange as well,but followed like sheep?
How did the water get in there? Is the engine water cooled? On my brothers small tractor the oil in the transmission is also used as the hydralic fluid.
In re using Mobile 1 for the hydraulic fluid; I was told by the X-Mark dealer that Mobile 1 runs cooler. I am sure that you all know that when you flow a lot of oil at a high temperature you get a lot of heat. The reservoir in my system is quite small so heat could be a problem. If you had a 10 gallon reservoir it would probably not matter much.
Yes, Mobil 1 is an expensive hydraulic fluid ($26 a gallon at Walmart), but that is what the manufacturer (Great Dane) calls for. At least the machine only uses about a gallon or maybe a quart more.
Donít have the slightest idea how the water got into the system. (Engine is air cooled.) When I drained the system, the oil was the typical milky color of water contamination. Condensation, sabotage, somebody left the reservoir cap off, who knows.
if you are not in any hurry, drain out old oil, let the water settle out, replace the oil into the system, run thru a bit then replace with new. the water has a way of hiding in systems so a flush is a good idea. reusing the old for the flushing avoids contaiminating the new oil with what ever.
Mineral Spirits is usually a safe solvent for flushing and cleaning. Just don't use for hydraulic brake components. Brake fluid seals and cups don't like petroleum based solvents.
I bought a used 4' Tiller for my tractor over the weekend and the gearbox gear oil was milky. I drained it and flushed it by filling with MS, running it to wash out, drained and refilled it with 90W. The MS really showed the milky color. I feel like I got a good cleaning doing it this way.
I sure wouldn't want any type of solvent in my expensive oil, might be ok, once you run it the heat would probably cook off anything bad, but I wouldn't do it. I have used clean used hyd fluid for flushing. but as above I would not want to contaminate the synthetic oil with anything.
w/g, if the hyd sys uses cyls, the rod brings the water in when they retract. you might be the first person that has ever looked at that reservour. surf