Used Combine Inspection Checklist: What to Check Before You Buy

Buying used · 10 min read

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A used combine is the hardest-working machine on a farm, and wear hides inside it where paint can't cover. The panels and the cab can look fresh while the threshing hardware is shot — and a walk-around at the lot won't show you that. A worn combine costs grain out the back and downtime in a ten-day harvest window. Here's how to inspect a used combine system by system before money changes hands.

Start with the machine's story

Hours tell you more than the year on the serial plate. A combine has two clocks: engine hours and separator (threshing) hours. Separator hours are the honest number — that's the wear the machine actually saw. A machine that averaged hard hours in corn every fall wore differently than one that ran short wheat harvests and sat the rest of the year.

Ask what crops it ran. Corn is the hardest on concaves, rasp bars, and grain augers; rice is brutal on everything; wheat and soybeans are comparatively gentle. Ask how it was stored — inside under a roof matters for electronics, belts, and tires. Ask who ran it: an owner-operator with a grease gun or a hired crew chasing acres? Ask for maintenance records — concave replacements, rotor or cylinder work, auger rebuilds, belt and chain replacements, gearbox work.

Threshing and separating: where the money is

On a rotary machine, open the rotor cage and inspect the rasp bars. They should have a crisp edge and consistent profile — bars that are rounded off, chipped, or visibly worn have lost their threshing aggression, which means more unthreshed grain going out the back. Look at the concaves: wires and bars should be intact, the concave holding its original shape — not bowed, patched, or worn thin in the middle. Check the concave clearance adjusters — if they're seized or stripped, nobody's been setting clearances, and that tells you how the machine was managed.

On a conventional (cylinder/walker) machine, check the cylinder bars the same way, and walk the straw walkers: look for cracked walker sections, worn crank bearings, and walkers that don't track evenly. A cracked walker frame is a breakdown waiting for harvest.

While you're inside, check the grain pan and sieves. The louvers should move freely in their adjustments; sieves that are stuck, bent, or missing sections can't be set. Look for grain and chaff packed where it shouldn't be, and shine a light through the machine — worn sheet metal in the threshing area means grain has been escaping through gaps instead of going through the sieves.

Grain handling: augers and elevators

Grain augers are consumables sellers conveniently forget to mention. Look into the sump and troughs at the clean grain and tailings augers: flighting that is worn thin, sharp-edged, or holed through the trough bottom is past its useful life. Check the bubble-up auger in the grain tank the same way. On the elevators, the chains and paddles should run straight and tight with paddles intact — worn paddles and slack chains mean grain damage and capacity loss when you can least afford it.

Unfold the unloading auger and check every section: flighting for wear, the tube for holes or thin spots (patches and weld repairs tell you the history), and the drive connections on both augers. Engage the unload drive slowly and listen — grinding, knocking, or a wobble at the joint means drive wear or a bent tube.

The header and feederhouse

The header does the cutting, and a worn header turns into a combine problem fast. On a platform header, check the cutterbar: every section sharp and intact, every guard straight and complete, hold-down clips adjusted and present. Run the reel and check each bat for straightness and the tines — missing or bent tines leave standing crop. Check the skid shoes; shoes worn through mean the header has been riding on the ground. On a draper header, inspect the belts for tears, missing slats, and frayed edges, and confirm they track straight.

Check the header auger (or the center feed drum on a draper): full flighting, all fingers present and spring-loaded. Then pull the feederhouse inspection covers and check the feeder chain and slats for wear, tightness, and missing slats. Pull the stone trap or rock door and look inside — the rock and debris tell you what the machine has been swallowing. Test the header reverser if the machine has one — a reverser that doesn't work is how a slug becomes a tow bill.

Engine, cooling, and the dirty side

Combines live in dust, and the cooling system shows it. Pull the air filter and hold it to the light — a filter run past its service life tells you the maintenance culture. Check the precleaner and intake plumbing for dust leaks past the filter; dusting an engine is the fastest way to kill one. Inspect the radiator and rotary screen: the screen should rotate freely, the fins clean and straight, not packed with chaff or bent from pressure washing. A combine that runs hot in October stops.

Check every belt you can see — main drive, separator drive, header drive — for cracking, fraying, glazing, and proper tension, and check the variable-speed sheaves for wear grooves. Then check the hydraulics: weeps at hose ends, cylinder seal leaks, and the oil's condition — dark, burnt-smelling oil on a machine with claimed recent service is a story that doesn't add up. Cycle every hydraulic function and watch for slow or jerky movement.

Structure, axles, and running gear

Walk the machine the way you'd walk any heavy equipment. Look for cracks at the high-stress points: the feederhouse pivot area, axle mounts, unloading auger hinge, and grain tank extensions. Note weld repairs — one clean repair is maintenance; a stack of amateur welds in the same area is a machine that's been breaking there repeatedly. Check the final drives for leaks and the axle pivots for play.

Check the tires or tracks: even wear, no sidewall cracking or chunking, matching sizes per axle. On tracked machines, inspect the belts for cuts and missing lugs, check tension, and look at the bogie wheels and idlers for wear and seal leaks. Mismatched tires on a drive axle or a track run loose tells you where the machine wasn't getting attention.

The cab and the electronics

Check that the HVAC blows cold and hot — cab air matters for long days and for keeping dust out of the electronics. Check the door and window seals; a cab that won't seal is a cab full of dust, which is also a cab full of problems for the displays. Check the seat, steering, and every control for smooth operation.

Power up every display. The machine should boot cleanly — no dead pixels, no persistent error codes, data showing from the yield monitor, moisture sensor, and GPS receiver. Ask which guidance and mapping unlocks are active, and whether they transfer to a new owner. Hardware locked to the previous owner's account or subscription is hardware you can't use until you sort the transfer, so confirm the status before you buy, not after. Check the harness for chafed, repaired, or rodent-damaged sections, and confirm the monitors, receivers, and cab hardware are included in the sale.

The live test run

Don't buy a combine you haven't heard run under load. Have the seller start it cold if possible and watch the exhaust. Engage the separator and header at operating RPM and listen: smooth running, no rhythmic knocking, no belt slap, no bearing howl above the normal roar. Walk around it while it's running and feel for unusual vibration.

If you can run grain through it — even a short pass — do it. Watch the loss monitors, check behind the machine for whole kernels and unthreshed heads, and watch the grain tank fill: evenly, with clean grain, not chaff and cracked kernels. Cycle the unloading auger under load and watch it swing smoothly, then take it through a turn and a short road-speed run to check the transmission, steering, and brakes. A combine the seller won't run, won't engage, or won't drive is telling you everything: walk away.

Records and the questions that matter

Ask for the service file: concave and rasp bar replacements, auger and elevator work, belt and chain replacements, gearbox or final drive repairs, any engine work. Ask when the sieves, concaves, and clearances were last set — and by whom. Ask about fire history directly: combine fires happen, and a machine that's been through one can hide heat damage in wiring and hydraulics for years. Ask how it was stored, whether it was parked loaded, and what the seller would fix if they were keeping it. That last question has ended more bad deals than any checklist.

Bring your mechanic if you can — they've seen the failure patterns on the exact model you're looking at. And if the seller won't let you open the rotor cage, pull the stone trap, run the separator, or power up the displays, that's the answer. Walk away.