Vehicles, Tractors & Heavy Equipment

A car or pickup needs the same few things checked over and over. The Navy's walk-around before a truck moves is a good habit for any vehicle: tires, lights, leaks under it, fluid levels, then the brakes and gauges once it runs (Equipment Operator, pp. 163–164).

The 12-volt battery and charging

• Reading the charge with a hydrometer (wet batteries with caps): below 1.240 at 80 °F, charge it; never let it go below 1.225 except in hot climates. For every 10 °F below 80 °F, subtract 0.004 from the reading (Navy Construction Mechanic 3 & 2, p. 166).
• A flat battery freezes. At 1.100 the acid freezes at 18 °F; at 1.220, at −31 °F; fully charged (1.285), not until about −95 °F. Check and charge batteries that sit, above all in cold weather (p. 168).
• Cold steals cranking power: at 0 °F a battery has about 40% of the cranking power it has at 80 °F (TM 9-8000, p. 289).
• Is it charging? With the engine running, a 12-volt system should read 13.2 to 14.5 volts (TM 9-8000, p. 383). Lower: check the belt, the wires and the alternator (rule of thumb).
• Clean the terminals with baking soda and water, and keep it out of the cells (Construction Mechanic, p. 167).
• Alternator rules: connect a charger or a booster battery + to + and − to −; never run the alternator with the battery disconnected ("open circuit"); never short its terminals (Alternator and Regulator Servicing, pp. 15–16).
• Jump-starting (rule of thumb): + to + first, then − of the good battery to bare metal on the dead car's engine, away from its battery, so the last spark is not beside the hydrogen. Remove them in the reverse order. Never jump a 12-volt system from a 24-volt one (many big trucks and machines): it can wreck the battery and starter "or even" cause "an explosion" (Equipment Operator, p. 95).
• Charging and caring for lead-acid batteries, and acid in the eyes: Off-Grid Power and its battery safety.

When it won't start

• Barely turns over, or a row of loud clicks: "you can be fairly sure there is a problem with the battery." Starters seldom fail unless overused: never crank more than 30 seconds without letting the starter cool (Construction Mechanic, p. 197).
• Turns over well but won't fire: it needs fuel, spark and compression, the same as a small engine (Engines guide). Old gasoline is the usual culprit (Fuel guide).
• Diesels: below.

Cooling: radiator, hoses and belts

• The pressure cap: systems run at 4 to 17 psi, and each pound raises the boiling point about 3 °F. Replace a cap only with one of the same rating (Equipment Operator, p. 46). Never take it off unless the engine is cold: "it will spray you with hot steam and coolant" (p. 48).
• Antifreeze: a mix of 60% ethylene glycol and 40% water gives the most protection; more glycol gives less, and pure glycol freezes not much below water. If you run plain water, add a rust inhibitor. Glycerin is the stand-in: it protects like alcohol and doesn't boil away (TM 9-8000, p. 238).
• Antifreeze poisons: its sweet taste draws animals and children (Equipment Operator, p. 46). Keep it capped and locked up.
• Watch the gauge. If the temperature starts to rise, stop and find out why; don't wait for the red (Equipment Operator, p. 98). Clean bugs and chaff out of the radiator by blowing through it backward (p. 45).
• Hoses: squeeze them. Replace any that are cracked or "mushy"; a soft lower hose can suck flat and boil the engine over (Construction Mechanic, p. 147).
• Belts: the Navy's rule of thumb is no more than ½ inch of give when pressed midway between pulleys (Equipment Operator, p. 47). Too tight wears out the alternator bearings (Construction Mechanic, p. 148).

Brakes

• Test before you move: pump the pedal three times, then hold it firmly for 5 seconds. The pedal should not sink; if it does, there is a leak (Equipment Operator, p. 164).
• Having to keep topping up the fluid means a leak. A soft, spongy pedal means air in the lines (Construction Mechanic, p. 277).
• The right fluid only. Use brake fluid marked DOT-3 (or what the cap says) (p. 267). Fluid with mineral oil in it (engine oil, ATF, hydraulic oil) ruins the rubber seals, and then the whole system must be rebuilt and flushed (p. 378). Silicone brake fluid "will not absorb or retain moisture" and keeps through long storage, but it does not mix with the ordinary (glycol) kind (Construction Mechanic Advanced, p. 150). Ordinary fluid draws water from the air, so keep the can sealed (rule of thumb).
• Bleeding the air out with a helper (Construction Mechanic, pp. 277–278; drawing):
  1. Fill the master cylinder. Push a clear hose onto the bleeder screw of the wheel farthest from it, with the hose end in a jar of clean brake fluid.
  2. Open the bleeder; the helper pushes the pedal down slowly as far as it goes. It may take six or seven strokes before the fluid comes without air. Close the bleeder before the pedal comes back up, so it can't suck air in (rule of thumb).
  3. Refill the master cylinder every three or four strokes, or it pumps air back in.
  4. When no more bubbles come, close the bleeder tightly. Do the next-farthest wheel, and so on.
• Brake dust from old shoes may be asbestos, "a substance that can cause cancer." Wear a filter mask (TM 9-8000, p. 655); never blow it out with air (rule of thumb).

Tires, flats and jacking

• Pressure matters both ways. Low tires flex, heat up and blow out; hard ones break cords and wear the center (Equipment Operator, p. 72). Don't mix radial and bias-ply tires on one axle (p. 73).
• Jacking (Equipment Operator, p. 76): park in gear with the brake on, block the wheels on the other axle, loosen the nuts before lifting, and put a plank under the jack on soft ground. "Do not leave the vehicle suspended on the jack": to work under it, set stands or solid blocks under the axle.
• Patching: feel inside a tire with a rag, not a bare hand: there may be a nail (Equipment Operator, p. 80). On a radial tire, patch only the middle of the tread, not the sidewall (p. 81; repairing a puncture). Bicycle-style tube patching: Bicycles & Carts.
• Split rims and lock rings kill. On many truck, tractor and implement wheels, a ring holds the tire on. A ring that isn't seated "may blow off, causing serious injury." Inflate to 5–10 psi, tap the ring home, and never stand in front of or over it: inflate inside a safety cage, or through a clip-on chuck from the side (Equipment Operator, p. 80; lock-ring rim; safety cage). With no cage, chain the wheel to something heavy and stand well aside (rule of thumb).

Fuel, filters, lights and fuses

• Drain the fuel filter's bowl: water and grit settle there. The Navy drains about a quarter pint from the filter before each day's work (Equipment Operator, pp. 28–29).
• Never wash an air filter in gasoline: static or friction can set it alight (Construction Mechanic, p. 87).
• A rusted muffler leaks carbon monoxide into the cab, "sometimes fatally" (Construction Mechanic, p. 91).
• Fuses: replace with the same rating, and find the fault first. A blackened fuse means a short; a clear one, too much load (Equipment Operator, p. 98). Never use foil or wire in place of a fuse (rule of thumb).
• Getting fuel out of tanks and testing it: Fuel guide.

Parking a vehicle for months

• The battery: check and charge it regularly, or it freezes when cold (Construction Mechanic, p. 168). Taking the negative cable off stops slow drains from clocks and computers (rule of thumb).
• Fuel: old gas gums up; stabilize it or drain it (Fuel guide). Water "forms by condensation in a partially empty tank" (Construction Mechanic, p. 130), so park a diesel with its tank full (Fuel guide).
• Shiny hydraulic rams: grease them before storage and wipe them before use (Equipment Operator, p. 102).
• Don't just idle it now and then. Long idling keeps plugs too cool to burn clean (Construction Mechanic, p. 208); if you start it, drive it until it is fully warm (rule of thumb).
• (Rule of thumb): park on boards or blocks off wet ground, pump the tires up, close the vents and keep mice out of the air box and wiring (they nest and chew).

A vehicle as a power source

A running car is a 12-volt generator. An inverter on the battery runs small loads; how to wire it, and why idling for hours to charge a house bank wastes fuel: Off-Grid Power. Never run it in a garage or near a window (TM 9-8000, p. 741), and never feed a house through an outlet (Engines guide).

Towing and getting unstuck

• Use a tow bar, not a chain or rope, for towing (Equipment Operator, p. 114). A rigid bar keeps the towed vehicle from running into the one pulling it (rule of thumb).
• Stand clear of any loaded cable, chain or strap. Wire rope "whips with great force" when it breaks; everyone should stay clear of its whole length (Equipment Operator, p. 278).
• Winching: don't wrap the cable round a bumper; it bends (Equipment Operator, p. 112). A snatch block on a solid anchor adds pulling power (p. 115; winching drawings; self-winching). Blocks and tackle, and safe rope work: Knots & Rope.
• (Rule of thumb): drape a heavy coat or a sack over the middle of a winch line to soak up a snap; pull slowly; never "snatch" with a chain.

📚 Go deeper: TM 9-8000 Principles of Automotive Vehicles — how every part of a vehicle works; Navy Construction Mechanic 3 & 2 — batteries, cooling, brakes and tune-ups; Navy Equipment Operator — daily checks, tires, towing and winching. Pictures: a cooling system's pressure cap, TM 9-8000 p. 245, Automotive battery, Hydraulic brake, Jump start (vehicle).

How a diesel works, bleeding air out of the fuel system, cleaning injectors and reading the smoke are in the Engines guide; gelling, water, fuel bugs and stand-in fuels are in the Fuel guide. What they leave out:

• Glow plugs. Cold diesel fuel is hard to light, so many diesels have glow plugs (or an intake heater) that warm the air before and while you crank (Construction Mechanic, p. 129). Turn the key to "on" and wait for the glow light, often 15 to 30 seconds, before you crank (Equipment Operator, p. 34; a glow plug). Hard starting only when cold often means a dead glow plug (rule of thumb).
• Cold starts. Diesels are "very difficult to start in cold weather" because the fuel doesn't evaporate; the Army's helpers are a flame heater in the intake and an ether shot (TM 9-8000, p. 200). Keep the battery charged: at 0 °F it has only 40% of its cranking power (p. 289). Never spray starting fluid into an engine while its glow plugs or intake heater are on: it can fire early and break the engine (rule of thumb).
• Ran out of fuel? Air got in. "Air lock in fuel line" is one of the first things to suspect (Practical Action Diesel Engine Repair, p. 12). Fill up, then bleed it from the tank toward the injectors as the Engines guide shows.
• Water in the fuel "will rust an engine" and causes hard starting and misfiring (Construction Mechanic, p. 93); it can rust the injection system until it fails (Equipment Operator, p. 26). Drain the filter bowl every day you run (p. 29).
• Keep your hands off injectors and their lines while the engine turns. The Navy warns that injector spray that gets through the skin "will cause blood poisoning" (Construction Mechanic Advanced, p. 132).

📚 Go deeper: Navy Construction Mechanic Advanced — diesel fuel-system overhaul; TM 9-8000, p. 200 — cold-weather starting aids. Pictures: Glow plug, Diesel engine.

Before you start (TRAC-SAFE, p. 29; checklist, p. 72): tire pressure, clean windows and mirrors, the seat set for you, the ROPS and seat belt, brakes, steering, lights, the slow-moving-vehicle sign, and the PTO shields in place. Oil, coolant, fuel filter bowl and hydraulic fluid as on any diesel (above).

The hitch. Pull loads only from the drawbar. "Many accidents occur when loads are hitched to axle housing or other parts of the tractor"; on the three-point hitch use only implements made for it. "Attaching implements to something higher than a drawbar can cause the tractor to roll over" (TRAC-SAFE, p. 48). Front-end weights help keep the front down (p. 29).

The PTO (power take-off) is the spinning shaft at the back that drives mowers, balers and pumps (NIOSH Alert 94-105, p. 3). Keep every shield and guard on it, and replace a guard that is open underneath (p. 7). The rules for using it are in the safety section just below.

Implements: lower them to the ground before you service anything or leave the seat (Equipment Operator, p. 235). Front-end loader: carry the bucket as low as you can on any slope (same page). Hauling a raised load is a known cause of overturns (TRAC-SAFE, p. 18).

On the road: lock the two brake pedals together, so a hard stop can't brake one wheel alone and swing the tractor round (rule of thumb).

📚 Go deeper: NIOSH TRAC-SAFE — causes of overturns and a tractor safety checklist; Navy Equipment Operator — loaders, backhoes and their safety rules. Pictures: tractor safety checklist, TRAC-SAFE p. 72, Three-point hitch, Power take-off.

How it works

A pump pushes oil from a tank (reservoir) through a valve you work with a lever, into a cylinder whose rod pushes out or pulls in; the oil goes back to the tank through a filter. A relief valve lets oil back to the tank when the pressure gets too high (Equipment Operator, pp. 100–101; a basic system). A small push on a small piston makes a big push on a big one: 100 pounds on a 1-square-inch piston pushes 500 pounds on a 5-square-inch one, but the big piston moves only a fifth as far (FM 5-499, pp. 19–20). That is how a bottle jack lifts a truck (the jack). The tank lets air bubbles out and the oil cool, so keep it filled to the mark: low oil overheats, or lets air into the pump. Work the levers smoothly; jerking wears the machine (Equipment Operator, p. 101).

Leaks, hoses and fittings

• Look, don't feel. Check hoses before and after work for cracks, splits, pinhole leaks, rubbing, heat and twisting (Equipment Operator, p. 103). Hunt for a leak with a piece of cardboard or wood held near the hose, never your hand (rule of thumb).
• Fitting a hose (FM 5-499, pp. 44–45): don't twist it (the stripe along it should run straight); leave some slack, because a hose gets shorter under pressure; wrap it with tape where it rubs; clamp lines often, but never weld them to their supports.
• New hose ends: many hoses take couplings you can fit in the field; cut the hose square with a fine hacksaw (24 or 32 teeth per inch) (FM 5-499, p. 49; field couplings).
• Pipe-thread compound: keep it off the first two threads so none gets inside (FM 5-499, p. 47).
• Quick couplers: put the dust plugs in when you unhook an implement, or tie a plastic bag over the ends (Equipment Operator, p. 103; quick couplers).
• Finding an air leak on the pump's suction side: pour oil over each joint and listen; the noise changes at the leak (FM 5-499, p. 137).

Clean fluid, the right fluid

• Dirt is the main enemy. Contamination causes "more hydraulic system failures than any other single source" (Construction Mechanic Advanced, p. 252). Clean round the filler before you open it (Equipment Operator, p. 101); cap open hoses and ports; never wipe parts with rags, whose lint clogs valves (FM 5-499, pp. 45, 113).
• Water gets in by condensation and turns to sludge; oil cooked above 250 °F breaks down and turns brown (Construction Mechanic Advanced, p. 253).
• Use the fluid the manual names. Hydraulic fluids are water-based, petroleum-based or synthetic, and the wrong one means draining, flushing and refilling (Equipment Operator, p. 43). "Do not mix hydraulic fluids or reuse old fluid," and filter what you pour in (Construction Mechanic Advanced, p. 250).
• In a pinch: no book in the library names a stand-in. (Rule of thumb): for a system that takes petroleum oil (most tractors and loaders), top up with clean petroleum hydraulic or tractor fluid of about the same thickness, then drain and refill with the right one when you can. Never brake fluid in a hydraulic system, and never hydraulic oil in brakes (Construction Mechanic, p. 378).
• Clean parts in clean solvent, not carbon tetrachloride, which ruins rubber seals (FM 5-499, p. 113).

Air in the system

Slower movement than normal can mean air in the system (FM 5-499, p. 138); air drawn into the pump makes it noisy and makes the system chatter (p. 137). It escapes in the tank, where the oil can foam and give it up (Equipment Operator, p. 100). Top up the tank first. (Rule of thumb): with the engine at idle, run each cylinder slowly all the way out and in several times, so the air goes back to the tank and bubbles out there.

Troubleshooting: FM 5-499 has tables for a pump that won't deliver, no pressure, noise, creeping, slow action and overheating, each with its causes and fixes (pp. 136–139).

📚 Go deeper: FM 5-499 Hydraulics — every part, and the troubleshooting tables; Navy Construction Mechanic Advanced — keeping equipment hydraulics clean. Pictures: a reservoir's design, FM 5-499 p. 34, single- and double-acting cylinders, Equipment Operator p. 102, Hydraulic cylinder, Hydraulic fluid.

Big trucks, some tractors' trailers and many machines stop with air: an engine-driven compressor fills tanks, and the pedal sends air to a chamber at each wheel (Equipment Operator, p. 88; a typical system).

• Pressures: the governor stops the compressor at about 125 psi and starts it again at about 100 (Equipment Operator, p. 89). Keep 100 to 120 psi; a warning must come on below 60 psi. A sudden loss means something burst (p. 99).
• Drain every air tank at the end of each day: water and oil collect, and "ice inside a brake system can make the brakes stop working" (p. 89).
• Spring brakes are the parking and emergency brakes: strong springs held off by air. Lose the air and they come on, at 20 to 45 psi; don't wait for that, stop safely when the low-air warning comes (p. 166). Never take a spring-brake chamber apart: the spring inside can kill (rule of thumb).
• Compressed air itself is dangerous: it can cut through skin and cause a fatal air embolism (Construction Mechanic Advanced, p. 195). Bleed an air line before you uncouple it (Equipment Operator, p. 395).

📚 Go deeper: TM 9-8000 — air, air-over-hydraulic and vacuum brakes; Navy Construction Mechanic Advanced — troubleshooting hydraulic and air brakes. Pictures: a typical air brake system, TM 9-8000 p. 680, a brake chamber, p. 684, Air brake (road vehicle).