Check for hydraulic contamination before the machine parks for winter

Around Oshkosh a lot of equipment parks from Thanksgiving to April. Planters, choppers and grain carts on the farms out toward Omro, skid steers and mini excavators on paving and landscape crews, forklifts in seasonal yards along I-41. The fluid that goes into storage is the fluid that comes out, and anything riding in it has a whole winter to rust a spool, pit a rod or settle into a valve. Oshkosh Hydraulic Line Repair sees the result every April: machines that ran fine in November and weep, stick or groan on the first warm day. Most of it was findable in the yard before the machine was put away.

The three contaminants and what each does over a winter

Water is the one that matters most here. It gets in as condensation when the reservoir breathes on a warm afternoon and a cold night, through a pressure washer aimed at a breather cap, or past a cracked filler cap. Lake Winnebago keeps the air damp and the freeze and thaw swings from October to December pull moisture in and out of the tank daily. Once inside, water rusts the chrome on cylinder rods and the steel spools in the valve block, thins the film that keeps the pump alive, and freezes in low points of the plumbing. Fluid that has emulsified turns milky and stays that way.

Particles come from three places: dirt through a torn or missing breather element, metal from a pump or motor that is wearing, and rubber crumbs from a hose that let go earlier in the season and was replaced without flushing. They settle to the bottom of the tank over winter and get stirred straight into the pump inlet on the first cold start in spring, when the fluid is thick and the filter is most likely to bypass.

Air shows up as foam in the sight glass, spongy controls and a pump that whines. Over a winter air itself does little, but it is a sign of a suction side leak, a low tank or a bad shaft seal, and every one of those gets worse with cold thick fluid in April. Find the source in the fall while the machine still runs.

How to check each one in the yard

Run the machine long enough to warm the fluid and work every function, then shut down and go through this list.

• Sample the fluid. Draw from the drain or the lowest fitting into a clear jar, not from the top of the tank where everything looks fine. Set it next to a jar of fresh fluid from the pail. Cloudy, milky, dark or smelling burnt tells you the story before any lab does. Let it sit overnight and look for a water layer and settled grit.
• Look at the filter. Check the bypass indicator if the machine has one. Better, pull the return filter and cut it open. Bright metal flakes point at a pump or motor. Black rubber points at a hose. Fine gray sludge is ordinary wear and dirt.
• Open the breather. The reservoir breather is the cheapest part on the machine and the most ignored. A torn, missing or plugged element lets in dirt and water for free. Replace it now, not in spring.
• Check the rods. Wipe each cylinder rod and run a fingernail across the chrome. Pits catch. A rod that is already pitting will chew seals the first week of spring, and a gland that is collecting dust is weeping now.
• Watch the tank while it runs. Foam or a level that drops with every function means air is getting in on the suction side. Look at the hose clamps and the pump shaft seal for a wet line.
• Wipe every fitting. Dust sticks to oil. Clean fittings that are wet again after five minutes of running are on the fix list. The failed hose guide explains which fitting leaks a wrench fixes.

Storage prep that keeps new problems out

1. Fill the reservoir to the full mark with the machine in its storage position. Less air in the tank means less condensation over the winter.
2. Retract every cylinder you can. Bucket curled, boom down, stabilizers up, header lowered onto blocks. Any chrome that has to stay exposed gets a coat of grease or a rust preventive.
3. Cap every open quick coupler with its dust cap. A rag or a plastic bag is not a cap. Couplers on implements that unhook for the winter are the usual way dirt gets into a tractor's remotes.
4. If the sample showed water, change the fluid now, before the machine parks. Water left in the system all winter does the damage whether the machine runs or not. If the fluid is clean, leave it and plan the filter change for spring.
5. Replace a bad breather, a weeping fitting and any hose with wire showing before storage. A hose with a cracked cover in November is a burst hose in April.
6. If you can, start the machine once a month, let the fluid warm, and move every function through its full travel. It keeps seals wet and moves any water off the low points.
7. Old fluid goes to a used oil collection point, not the trash. Wisconsin bans used oil from landfills under Wis. Stat. 287.07, and most auto parts stores and several Winnebago County municipal drop sites take it.

What it costs to have us do it

Labor inside those ranges is $95 to $140 per hour. Every row is on the pricing page. Fluid and filter changes are quoted per machine by reservoir size and grade, and the winter fluid guide covers which grade to put in.

The cylinder rows are on this table for a reason. Nearly every spring reseal we do on a stored machine traces back to a rod left extended or water left in the tank. The inspection costs less than half of the smallest reseal.

Spring startup

When the machine comes out in April, let it idle until the tank is warm before working anything under load, then walk every fitting and rod again with a rag. Change the filter after that first warm run so it catches whatever settled over the winter. If the fluid looked fine in November and the tank was full and capped, that is usually the whole job. If you skipped the fall check, the emergency page has the after hours numbers for the day a stored machine reminds you.

To have the truck do the fall walk, call or send the form with the machines and the town. Late October and early November fill up around Oshkosh, so book before the first hard freeze.