In evaluating a used tractor, follow an organized procedure to be sure you don't overlook anything important. It is a good policy to divide evaluation into two stages, external evaluation and internal evaluation.

Any evaluation will be on a relative basis. Higher standards must obviously be used for evaluating a late-model tractor than would be used for an older unit.

External evaluation. First, give the tractor a quick over-all visual inspection, making mental notes of items that should have further examination. Then make a detailed inspection, including at least the following items:

Grease or oil leaks. Check all shafts, bearings, seals, gaskets, and so on, for evidence of external leaks. If any are present, try to determine if they are major or minor. Dust accumulations over old grease spots generally are not indicative of a major problem. Fresh grease spots, particularly larger ones, and grease spots on the floor under the tractor justify detailed investigation.

Engine block and cylinder bead. Examine the engine block and cylinder head for external cracks or freezing damage. Major damage is difficult to repair, and can mean future trouble. There is also the possibility that internal damage may have occurred.

Cooling system. Examine the cooling system for evidence of leakage or overheating. Also, look for evidence of repair to the radiator core. Metal surfaces will usually show signs of stains caused by coolant leakage. Look for evidence of engine overheating, such as stains around the radiator fill cap or overflow tube. Also, check air passages through the radiator core for blockage with trash, bugs, and so on. Debris contributes to overheating, and may be difficult to remove. Remove the radiator cap and look for excessive mineral deposits inside the top tank--they may indicate the need for a complete commercial radiator flushing and cleaning.

Frame and castings. Examine the transmission and final drive housings and other tractor frame components for evidence of cracks, welds, and so on. Welds in major casting or frame components indicate that the tractor has had some rough treatment.

Tires. Tires wear with use and eventually have to be replaced. As tire wear increases, slippage also increases when the tractor is under load. Examine tires carefully for cuts, bruises, sidewall or radial cracks, and so on. Cuts or cracks that expose tire cords can cause rapid tire deterioration.

Wheels. Examine wheels, hubs, and rims for evidence of damage. Inspect wheel tread adjustment systems to be sure they are in working condition. Stand behind the tractor as it is being driven away from you, and watch for wheel wobble. Wheel wobble strongly suggests a sprung wheel, rim, or axle .

Protective shields and guards. For your own protection and the protection of others, be sure that all protective shields and guards are in place and in good operating condition. Check in particular to see that the master shield for the pto stub is in place. Also, be sure that all decals that include operating instructions and safety warnings are present and legible.

Rollover protection. Protective cabs or rollover frames and seat belts are always desirable, particularly if the tractor is to be operated by inexperienced people or hired help. With very few exceptions, all tractors manufactured after October 25, 1976, are required by OSHA regulations to be equipped with rollover protective devices if the tractor is to be operated by hired help. (This is not mandatory if the tractor is operated exclusively by the owner or his immediate family,)

Paint. A good paint job with new identifying decals will enhance the general appearance and sale of most used tractors. The paint job alone, however, adds nothing to the dependability of the tractor. A sloppy paint job or indications of poor preparation for repainting might be taken as a warning signal.

General. Make a second inspection of the general appearance of the tractor. Do the ignition system and electrical system wiring harness appear to be intact and in good shape? Do the hours of use, as shown on the tractor hour-meter, appear to agree reasonably with the stated age and the general appearance of the tractor? Does there appear to be any reason to question the stated age of the tractor? If so, check the tractor serial number against the manufacturer's list of serial numbers by year of manufacture. All reputable dealers will have this listing, at least for their own line of tractors.

Internal evaluation. Detailed internal evaluation of a used tractor is difficult, and at best can only give indications of actual internal conditions. A number of checks, however, can be made which will provide a prospective buyer with some means of making an educated guess as to the actual internal condition of the several component parts. The checks and tests discussed in the following paragraphs should be investigated in the order listed. Thermostat. The function of the thermostat is to prevent the cooling liquid from circulating through the radiator until the engine block has become completely warmed up. To check the thermostat, start the engine when cold, and run at a fast idle. Immediately remove the radiator cap and look for turbulence in the cooling liquid. If cooling liquid is being pumped directly to the top of the radiator when the engine in cold, it is indicative that the thermostat is stuck open, or has been removed. An open thermostat will cause slow engine warmup, excessive engine wear, and higher fuel consumption. If the thermostat has been removed, it may indicate a history of engine overheating.

Transmission lube contaminants. Transmission lubricants slowly become contaminated with metal particles worn from transmission gears and hearings. To check this, remove the transmission drain plug and drain approximately one-half pint of lubricant into a clean glass container. Add about a quart of diesel fuel or petroleum solvent to the sample and stir until thoroughly mixed. Then place a magnet in the diluted mixture and stir for 15 to 20 seconds. A small amount of metal particles adhering to the magnet is reasonably normal. A large amount indicates transmission wear and probably a need for a drain and refill. The presence of metal chips and broken particles indicates the possibility of chipped or broken gear teeth or damaged bearings. This could be serious.

Engine and transmission noises. Start the tractor engine and let it warm up thoroughly. Listen for knocking or other unusual sounds at idle speed. Accelerate the engine rapidly to full throttle several times. Is acceleration smooth and positive? Let the engine operate at full governed rpm briefly. Again, listen for unusual engine sounds. Remember, diesel engines are noisier than spark ignition engines and may tend to knock on acceleration.

Check clutch operation, and operate the tractor in an open area, shifting through each gear. Shifting should be smooth and easy. Be sure to follow instructions in the Operator s Manual. Many manual tractor transmissions are NoT designed to shift on-the-go.

Exhaust smoke. Look for blue or black smoke, both when starting up and accelerating the engine. Blue smoke indicates oil burning, whereas black smoke indicates an overrich operating mixture for the spark-ignition engine, and possibly faulty combustion for a diesel engine.

Batteries. Tractor batteries, like car batteries, do not normally last the life of the tractor. Larger tractors, particularly diesels, may have two or more 12-volt batteries. Have a dealer service representitive check the specific gravity and voltage of each battery cell. The specific gravity reading will indicate the degree of charge in each cell, and a low voltage reading will indicate a weak or possibly dead cell.

Air cleaner. Many older tractors will be equipped with oil-bath air cleaners, while more recent models will probably have dry-type cleaners. With the oil-hath cleaner, remove the oil cup and examine its contents. A low oil level or more than a quarter of an inch of dirt and sediment in the bottom indicate service neglect. With the dry-type cleaner, excessive dust and dirt in the filtering element also indicate service neglect. obvious neglect of the air cleaning system is indicative of poor tractor maintenance .

Engine compression test. The engine compression test is not infallible, hut is a relatively quick method of obtaining considerable information about the internal condition of the engine. Most farm machinery dealers are equipped to run the compression test on spark-ignition engines, but some may not have this equipment for diesels. If a compression test is desired, ask the dealer to have his service representative or mechanic run it for you. A complete compression test involves two steps: measuring the compression pressure built up inside the combustion chamber of each cylinder as the engine is being turned over by the starter at normal cranking speed; and adding 2 to 3 tablespoons of motor oil (preferably SAE-40) to each cylinder, and then repeating the test. For those not particularly familiar with motor mechanics, a dealer or competent mechanic should be relied upon to interpret test results. The following are some of the factors that may be indicated by an engine compression test:

A comparison of the compression pressures of the engine as tested and the compression pressure specifications for the engine when it was new.

The uniformity. or lack of uniformity, of compression pressures among the individual cylinders of the engine as tested.

A general picture of the wear to cylinder walls, pistons, and rings for the engine tested.

The possibility of a burned or damaged valve in one or more cylinders.

The possibility of a blown cylinder head gasket, either between a combustion chamber and the cooling medium or between two adjacent combustion chambers.

Rely on a competent mechanic for an interpretation of compression test results, but remember, only a complete engine tear down can positively substantiate any diagnosis. As a general rule, an engine compression test is more important and more meaningful with a late-model tractor than for very old models.

Dynamometer test. Most farm machinery dealer shops are equipped with a pto dynamometer for measuring the total pto horsepower outpUt of a tractor. This is an excellent way to determine how nearly a used tractor can come to delivering its original horsepower output. Here again, this test is probably more significant for late-model tractors than for older ones.

Determining horsepower and estimating value. The National Farm Power Equipment Dealers Association publishes a reference titled "Official Guide--Tractors and Farm Equipment" which lists serial numbers and Nebraska Tractor Test data for various makes and models of tractors. It also lists average resale prices according to the year of manufacture. The prices should he used only as general guidelines and do not reflect higher freight costs for shipping tractors to the west coast. This publication may he available for reference from your local bank or agricultural lending agency or farm equipment dealer.

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