How To Check Fluid Levels

[MikePhua]

Why Fluid Levels Matter More Than Most Owners Think
For a compact machine like a skid steer, keeping an eye on fluid levels is as important as fueling it up. Engine oil, hydraulic fluid, chain case oil, and coolant are not just consumables they are what keeps pumps alive, bearings from welding together, and hydrostatic drives from turning into scrap.
Industry surveys on mobile hydraulic failures suggest that well over half of premature failures are related to fluid problems contamination, wrong grade, or simple low level. In other words, a few minutes with a rag and dipstick can literally save thousands of dollars in repairs over a machine’s life.
Many first time owners or small contractors pick up a used skid steer with no operator’s manual and no walk through from a dealer. They see a few caps, a sight tube, maybe one dipstick, and start guessing. That’s where trouble begins.
This article walks through the major fluids on a typical skid steer, explains what each does, how to check it, and what to watch for. The focus is on simple, repeatable routines that a new owner can do with basic tools in a driveway or small shop.
Know Your Machine And Its Fluids
Before checking anything, know roughly what you’re looking at. A typical skid steer or compact track loader will have at least these major fluids

• Engine oil
  
• Hydraulic system oil
  
• Chain case or final drive oil (sometimes called chain case fluid)
  
• Coolant (antifreeze mix)
  
• Fuel (diesel)
  
• Occasionally separate axle or planetary oil on certain designs
  

Older machines may share hydraulic and hydrostatic drive oil in one reservoir. Newer models often use common reservoirs but have more sight gauges and warning systems.
Operator’s manuals usually list fluid capacities in gallons or liters. For example, a mid size skid steer might hold

• Engine oil around 8–12 quarts (7.6–11.4 liters)
  
• Hydraulic reservoir 20–30 quarts (19–28.5 liters)
  
• Chain case 3–5 gallons (11–19 liters)
  

Those numbers are approximate and vary by brand and model, but they’re useful for sanity checking. If you “blindly” pour 10 gallons into a hydraulic tank that normally holds about 25 quarts, you know something is off.
If a manual is missing, most manufacturers now publish them online by model and serial number. It’s worth printing the fluid chart and laminating it for your shop wall.
Engine Oil Checking Made Routine
Engine oil is the one fluid most car owners know, and it’s similar on a skid steer.
Typical steps

• Park on level ground
  
• Idle the engine briefly, then shut it off and wait a couple of minutes so oil drains back to the pan
  
• Open the rear or side engine compartment
  
• Locate the dipstick (usually yellow or bright colored handle)
  
• Pull it, wipe it clean, reinsert fully, then pull again
  
• Check that the level lies between “LOW” and “FULL” marks
  

Key tips

• Do not “top off” past the full line. Overfilling can cause foaming and high crankcase pressure.
  
• Watch the color and consistency. Fresh diesel oil is amber to blackish; thick sludge, metallic sheen, or coolant smell are warning signs.
  
• A new owner of a used machine should change engine oil and filter almost immediately, unless there is clear evidence it was just done, because service history is rarely complete.
  

As a rough rule, many contractors change engine oil every 250 hours on Tier 3/older machines and 250–500 hours on cleaner burning newer engines, depending on manufacturer recommendations and duty cycle.
Hydraulic Fluid Understanding Sight Tubes And Gauges
Hydraulic fluid is what actually moves the arms, bucket, and often drives the wheels or tracks. Low or foamy hydraulic oil will show up as noisy pumps, jerky movements, or overheating.
On many machines the hydraulic tank is behind the cab or integrated into the frame. Common level indicators are

• A clear sight tube on the side of the tank
  
• A round sight glass showing a band of oil
  
• A dipstick under a filler cap on older models
  

Basic procedure

• Park the machine on level ground
  
• Lower the lift arms fully to the ground and rest the attachment flat this matters because raised arms have cylinders full of oil, which lowers tank level
  
• Shut the engine off and wait a minute to let air bubbles rise
  
• Read the sight glass or tube the oil should be roughly mid window when cold
  
• If using a dipstick, follow the machine’s instructions some specify checking with engine off, others at idle
  

One common confusion is capacity. System capacity (hoses, cylinders, tank, and components) may be listed in gallons, but the reservoir itself holds less, often around 20–30 quarts on a mid size skid steer. Pouring in “system capacity” when refilling only the tank after a filter change can overfill it badly.
Signs the hydraulic oil needs attention

• Milky color indicates water contamination
  
• Dark burnt smell suggests overheating
  
• Metallic glitter hints at severe wear inside pumps or motors
  

Manufacturers often recommend hydraulic oil and filter changes every 1,000 hours, but in dusty, wet, or abusive conditions, many operators cut that interval down.
Chain Case Oil The Hidden Drive Lifeline
The chain case is the cavity in the lower frame where drive chains or final drive sprockets live. It’s easy to forget, because it often has no obvious dipstick. But that oil bath is critical it lubricates chains, sprockets, and sometimes bearings.
Common ways chain case level is checked

• A small plug on the front or side of the chain case
  
• A combination fill/check hole at a certain height
  
• On some later designs, a sight gauge protected by a welded guard tube
  

Simple check method on many machines

• Park on level ground
  
• Locate the check plug on the chain case front or side
  
• With the machine safely secured (parking brake on, engine off), remove the plug
  
• Insert a clean finger to the first knuckle
  
• If you can touch oil at that depth, the level is typically acceptable
  

If the chain case has not been checked in years, the first fluid that dribbles out when the plug is removed may not be oil at all but water and milky sludge. Condensation and leaky access cover gaskets allow water into the case over time.
Practical steps if you find milky oil

• Drain or pump out as much of the contaminated fluid as possible
  
• If access allows, remove the top inspection cover on the chain case to look inside
  
• Flush with a light solvent such as kerosene using a hand sprayer until the milky residue is gone
  
• Allow it to drain thoroughly
  
• Refill with the recommended oil to the proper level, then recheck after a few hours of operation
  

Some owners go further and add a retrofit drain plug at the lowest point of the chain case to make future service easier. This must be done carefully to avoid weakening the case or creating a leak point that can catch on debris, but when done well it turns a messy job into a quick task.
Coolant Levels And Overheating Prevention
Engine coolant often gets less attention than engine oil, yet overheating is one of the fastest ways to shorten engine life.
Typical cooling system features

• A pressurized radiator cap
  
• A plastic coolant overflow or expansion tank with “COLD” and “HOT” marks
  
• Hoses routed in tight spaces that may be hard to see
  

Checking basics

• Only open the radiator cap when the engine is cold. Hot pressurized systems can spray scalding coolant.
  
• On most machines, checking the overflow tank level is enough. The coolant should be between low and high marks when the engine is cold.
  
• Look for proper coolant mix (often 50/50 ethylene glycol and water) rather than plain water, which has poorer boil protection and corrosion control.
  

Many older used machines arrive with mystery coolant. When in doubt, draining, flushing, and refilling with fresh premix of the correct type gives a clean baseline. For diesel engines with wet sleeves, using coolant that meets the engine manufacturer’s spec is important to avoid liner pitting.
Fuel System Cleanliness And Water Management
Diesel fuel for off road equipment is often stored in bulk tanks or small transfer tanks. Contamination with water or dirt shows up as plugged filters, poor starting, or injection system trouble.
Good habits include

• Draining water separators regularly many have a clear bowl and a drain valve
  
• Replacing fuel filters at the intervals listed for your machine often 500 hours or sooner in dirty conditions
  
• Keeping transfer tanks and storage tanks closed and using proper caps to limit dust and rainwater entry
  

A new skid steer owner should locate the primary and secondary fuel filters, note part numbers, and keep at least one spare set on the shelf.
Used Machine Reality Starting From Zero
In many real world cases, a new owner buys a used skid steer from an auction, small dealer, or private seller with only a vague handshake assurance that “everything was just serviced.” Relying on that statement can be expensive.
A smart “baseline service” for a newly acquired machine usually includes

• Engine oil and filter change
  
• Hydraulic oil filter change and fluid top off (or full change if there are signs of contamination)
  
• Chain case oil inspection and change if the fluid looks wrong or age is unknown
  
• Coolant check and likely flush and refill
  
• Fuel filters replacement
  
• Grease all pivot points and pins
  

The cost of this complete first service may feel high, but compared to repairing a destroyed hydraulic pump or replacing chain case components, it is usually cheap insurance.
Reading The Clues Color, Smell, And Texture
Even without lab tests, simple observations tell a lot about fluid health.
For engine and hydraulic oil

• Clear to amber, with a normal oil odor typical of in service fluid
  
• No visible metal flakes
  
• Not foamy or milky
  

Engine oil will turn black quickly in a diesel, which by itself is not a problem. What matters is contamination and viscosity.
For chain case oil

• Should look like gear or hydraulic oil, depending on what the manufacturer specifies
  
• Milky tan or gray fluid indicates water mixed in
  
• Clear water under a layer of oil suggests standing water in the bottom of the case
  

For coolant

• Should be colored (often green, yellow, orange, or pink, depending on type) and relatively clear
  
• Rusty, brown, or thick coolant suggests internal corrosion and long neglected service
  

If you see or smell fuel in engine oil, or oil in coolant, those are advanced warning signs that need professional diagnosis.
Building A Simple Fluid Checklist
A new owner can quickly create a one page checklist to hang in the shop or cab. For example

• Daily or every use
  • Walk around visual check for leaks and puddles
    
  • Engine oil level
    
  • Coolant level in overflow tank
    
  • Quick glance at hydraulic sight glass
    
• Weekly
  • Clean around filler caps and vents
    
  • Inspect hydraulic hoses for rubbing or wet spots
    
  • Check fuel water separator
    
• Monthly or every 50–100 hours
  • Chain case level check
    
  • Grease all fittings
    
  • Inspect drive chains, sprockets, and cylinders for unusual wear or play
    

Using hours instead of calendar time makes sense for seasonal machines. A unit that only runs 100 hours a year but lives outdoors may still need annual fluid checks because of condensation and weather.
Why Manufacturers Push Preventive Maintenance
Skid steer and compact loader manufacturers have learned over decades that many major failures trace back to skipped basic service. Warranty data and field reports show patterns

• Pump and motor failures linked to dirty or wrong hydraulic fluid
  
• Chain and sprocket damage in chain cases that were never checked
  
• Engines damaged by overheating due to neglected coolant systems
  

To reduce these, modern designs add more sight glasses, better access to filters, and electronic alerts. But even the best warning system can only help if the operator understands what it means and responds properly.
A machine that is checked and serviced according to schedule often runs thousands of hours longer before major overhauls. For a small business, those extra hours can mean the difference between a machine that pays for itself and one that is constantly down.
A New Owner’s Story From Confusion To Confidence
Imagine a new contractor who buys a mid 1990s skid steer with no book, just a promise that “everything’s good.” After a few days, he notices vague steering and slow lift but has no idea whether hydraulic oil is low or if there’s a mechanical issue. There’s a tube next to a tank, but is that the right level? He reads that the system holds 10 gallons, so he pours that into one reservoir, assuming it’s right.
Only after talking to an experienced mechanic does he learn that the tube is actually a level indicator and should only be half full when cold. The “10 gallons” listed applied to a full system flush, not just topping a reservoir. He ends up draining the excess, reusing clean oil in the chain case, and finally getting everything into proper range.
From then on, he keeps a notebook in the cab listing

• Date and hours when fluids were changed
  
• Brand and type of fluids used
  
• Any leaks or issues noted
  

Within a few months he goes from guessing at caps and tubes to having a consistent routine. Breakdowns decrease, and his confidence in the machine increases.
Key Takeaways For Checking Fluid Levels
For a new owner or operator, the essentials boil down to a short list

• Learn where every fluid check point is on your specific machine
  
• Use level ground and proper positions (arms down, engine off when required) for accurate readings
  
• Do not assume that “system capacity” equals “reservoir fill amount”
  
• Treat milky or discolored fluids as a warning, not a cosmetic issue
  
• Baseline all fluids and filters on any used machine you bring home
  
• Keep a simple log so you know what was done and when
  

Once fluid checks become a habit, they take only a few minutes per day. That small investment pays off in reliability, reduced repair costs, and peace of mind every time you turn the key and go to work.