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Listening To Your Tractor : Part 3
by Curtis Von Fange
In this series we are continuing to learn the fine art of listening to our tractor in hopes of keeping it running longer. One particularly important facet is to hear and identify the particular noises that our mechanical beast makes. Even though our attention is usually focused on the task at hand, that is, the bushogging, disking, etc., it is odd how our ears will pick up the smallest unusual noise that it hears. It's like listening to an orchestration of music and hearing the flutist make a misguided squeak on the instrument. For some reason that wrong note sticks out over everything else that is right. It's the same way with the steady hum drum of the tractor. An unusual noise will stand out like a sour note and immediately draw our attention. It is important to recognize those sour notes and make the appropriate decisions on what the problem might be.
Many noises are temperature-related noises. For example, when the tractor is first started up one might notice a ticking sound coming from the side or top of the motor. After the engine warms up the ticking may disappear and not show up anymore until the next morning. This is usually attributed to either hydraulic lifters on the newer tractors or the tappet clearances on older ones. Hydraulic lifters are like small hydraulic pistons that take the rotary lift from the cam shaft and transfer the motion to linear lift through the push rod to the rocker arm. When the oil is cold and the lifters are old accumulated varnishes in the lifter causes the piston to remain collapsed. When the oil warms up sufficiently the piston bore expands enough to let it move up and down in the bore of the lifter. If there is extreme varnish in the bore then the lifter will tick even after warm up. Sometimes an oil additive will be adequate to help dissolve the varnish buildup and help the lifter quiet down. If the lifters are noisy all the time they should be replaced to prevent rocker arm damage. On the older style tractors the engines used solid lifters with an adjustment between the push rod and rocker arm called the tappet clearance. An excessive tappet clearance will cause a noisy tapping or ticking sound especially when the engine is cold. After warm up the metal parts expand and close up some of the looseness. Check the engine manual for proper clearances and the appropriate temperature for testing and adjusting the tappets.
Another cold related noise is the high pitched squealing sound either from the front of the tractor or underneath the seat. This sound is usually related to a pump trying to move cold oil. It can be the engine oil pump, the hydraulic pump in the front of the tractor, which runs the loader, or, perhaps, the hydraulic pump in the final drive casing which runs the three-point hitch. Best advice is to keep the engine rpm's relatively low until the oil warms up enough to circulate freely. One also might check the oil viscosity number to make sure the correct weight is being used for the corresponding outside temperature. After the tractor has warmed up sufficiently this noise will usually disappear. If the hydraulic pump still likes to squeal when the loader valves are actuated check to make sure the pump has the correct inlet and outlet hoses attached. For example, if the outlet hose is too large the pump may be pumping the hydraulic oil out of the pump faster than the inlet hose can deliver the oil from the reservoir. This condition, called cavitation, can cause excessive wear on the pump because it could be operating under no oil conditions. It is always wise to let the tractor idle for a little bit to let the fluids come up to normal operating temperatures before putting the unit in working conditions.
A more ominous noise is the deep throaty knock that comes from the engine after it initially starts in the morning. This noise can disappear quickly after the oil starts to circulate. When clearances get excessive on the crankshaft journals the oil runs out quickly after the unit is shut off. An overnight cool down shrinks the crank and accentuates the distances leaving a void between the journal and bearing. This void causes the knocking noise on early morning start-ups. It is an indicator that the bottom portion of the motor is in need of some crankshaft journal measuring and attention. If the noise persists after the oil pressure comes up or is heard while the engine is running then the motor should be switched off and the motor taken apart and repaired. If it is run for any length of time while knocking the odds get real high that the crankshaft will be permanently damaged. That spells big bucks for replacement.
Other temperature related noises include a high pitched whistling sound coming from the front of the tractor. Look for punctured or cracked radiator hoses. When pressure builds up in cooling system and the motor is overheating the coolant can shoot out the tiniest fissure in old rubber hoses. Also check for a weak radiator cap or pitted surfaces on the seating components of the cap. Occasionally there might be a deep howling noise from the front of the transmission or rear of the engine when the clutch is engaged. This usually means the pilot bushing or bearing between the flywheel and transmission main shaft has dried out and is in need of replacement. This condition can also cause a grinding of gears in the transmission when trying to shift the unit into gear from a standing still neutral position. Many times the howling will disappear after the unit has warmed up because the remaining grease in the bearing has warmed up enough to provide some lubrication. A repair should be in the near future though.
There is whistling sound that is independent of the temperature of the unit. Look for a partially plugged air filter or air inlet screen. Leaves, weeds, and debris will cause the air to have only a small opening to get through which causes the whistling. Remove and clean accordingly.
If a battery is not maintained adequately a layer of lead oxide will build up between the battery post and the terminal on the cable. It is recognized as a blackish crust that keeps the electricity from flowing to the starter. When the starter is engaged this type of oxidation will show up as a type of hum. It almost sounds like someone is holding down the middle C key on an accordion. Of course, the starter won't start but the hum is there. Similarly, this bad connection can also keep full voltage from getting to the starter and can imitate a low battery condition. A rapid fire clicking sounds as the starter solenoid repeatedly engages and disengages due to low voltage. Remove the battery terminals, clean with a wire brush post cleaner and try again.
One disturbing noise is a steady clicking from the transmission when the tractor is in a particular gear as it drives down the road. A missing gear tooth is the inevitable cause. Removal of the transmission cover will verify. It is best not to use that particular gear as any load can cause more teeth to dislodge, get into other gears/bearings and cause more extensive damage. If you don't really want to repair it this year, change the fluid and feel around in the housing for the missing teeth. If they are found install fresh or filtered fluid and simply don't operate the unit in the offending gear. Of course, there is no guarantee that your boy won't drive in that gear, but that is the risk I guess.
Listen for other noises like a grinding noise when the brakes are applied. Check the brakes for worn linings. Older tractors had riveted linings which, when worn down, grind into the drum leaving grooves. If caught soon enough they can be turned out with a lathe. Otherwise a new drum will be needed. Likewise, worn clutch linings will also grind into the flywheel when the clutch is engaged. This condition will quickly cause more serious damage to the flywheel and pressure plate and should be given immediate attention.
Of course there are the typical rattles and clunks that most tractors with their corresponding attachments tend to make. Look for loose three point hitch brackets, loose bolts, or just plain worn out parts. Some of these items can be procured at a farm store for replacement; others can be corrected by a simple bolt replacement. Keep in mind that the manufacturers did not intentionally send the units out in a rattling state. By locating and correcting the myriad of rattles the tractors life span will be effectively extended.