The Essential Bush Mechanic Skills for Overlanders

The Bush Mechanic’s Golden Rules: Observe and Inspect

Before we touch a single tool, you must adopt the bush mechanic’s mindset. Your most powerful skill is not wielding a spanner, but your power of observation.

The Vibration Rule

Your vehicle will be exposed to continual, destructive vibration on corrugations and rough tracks. Things will work loose. The golden rule is to inspect your vehicle often. Every major stop, and at least once a day, do a “walk-around.” Check for anything loose, hanging, or leaking.

The Sound Rule

Learn to listen to your vehicle. You know its normal hums, whirs, and rattles. If you hear any new or unusual noise—a squeal, a clunk, a hiss, or a grind—investigate it immediately. A small noise is almost always a warning for a big failure.

Phase 1: Pre-Trip Vehicle Familiarization

You can’t fix what you don’t understand. Your “bush mechanic” training starts in your driveway, long before you leave.

Get to Know Your Vehicle’s Anatomy

Open the bonnet. Lie on the ground and look underneath (when it’s safely parked!). Get to know what your engine bay and chassis should look like.

Take “Before” Photos

Use your phone to take clear photos of your engine bay, your suspension components, and the routing of your drive belts. When something is broken or has fallen off, these photos are an invaluable “how-to” guide for putting it back together.

Hunt for Leaks

Your best diagnostic tool is dust. Any sort of dust adhering to spilt or weeping fluids is a clear sign of a problem. Look for this “caked-on” dust on:

• Shock absorbers (a blown shock will be oily and dirty)
• Transmission and differential seals
• Around the engine block
• On brake lines

Know Your Fluids

Learn to check all your fluid levels, both hot and cold. This includes engine oil, coolant, brake fluid, clutch fluid (if applicable), power steering fluid, and transmission fluid.

The Tyre Check

Every single time you stop and get out of the vehicle, make it a habit to walk around and look at your tyres. A quick glance can spot a slow leak or a sidewall bulge before it becomes a high-speed blowout. Repairing a puncture in the nick of time will save you from destroying a valuable tyre.

Correct Jacking Points

Using the wrong jacking point can damage your vehicle or cause the jack to slip.

Solid Axle (e.g., old Land Cruiser, Hilux)

For the rear, place the jack under the differential “pumpkin” (for a full lift) or under the axle tube as close to the wheel as possible. For the front, use the axle tube.

Independent Front Suspension (IFS)

To lift a front wheel, place the jack under the lower wishbone (control arm), as close to the wheel as possible. Jacking on the chassis will require you to lift the vehicle much higher as the suspension droops.

Air Jacks

These are great, but be careful. Place them at the same strong points (near the wheel) and ensure they are far away from the hot exhaust, which will melt the bag instantly.

High-Lift Jacks

These are a powerful but notoriously unstable tool. Never use them for changing a tyre unless it’s your only option. They are best used for lifting a vehicle out of a rut (lifting and pushing sideways) and should always be used with extreme caution.

Field Repair Guide by System

1. Electrical System

If you see smoke: DISCONNECT THE BATTERY IMMEDIATELY. Always disconnect the negative (black) terminal first. Have your fire extinguisher ready.

Fuses

Find your fuse box (you may have one in the cab and one in the engine bay). Carry a full set of spare fuses.

Always replace a blown fuse with one of the same amperage.

If you don’t have a spare, you can “borrow” one from a non-critical circuit (e.g., the radio or cigarette lighter) to get a critical one (e.g., fuel pump or ECU) working.

Vehicle Won’t Start

Check Connections: Are the battery terminals clean and tight?

Check Battery Voltage: Use a multimeter. A healthy starter battery should show ~12.6-12.8 volts. A battery reading 12.0 volts is effectively flat and will not start the vehicle.

Test Connections: Put the red multimeter lead on the red positive battery terminal and the black lead on the vehicle’s chassis (a solid metal part). This reading should be the same as the one across the battery terminals. If not, you have a bad earth strap.

Testing Fuses

Set your multimeter to 20v DC. Earth the black lead (to the chassis or negative battery terminal). Touch the red lead to the two small metal tabs on top of a fuse. A good fuse will show voltage on both sides. A blown fuse will show voltage on one side and zero on the other.

Accessory Wires

Use the right thickness of wire for accessories like fridges. Thin wires cause a voltage drop, meaning your fridge won’t cool properly and your battery will drain faster.

2. Brake System

New Brakes Overheating

After fitting new brake shoes, they may rub slightly. This generates heat. After a short drive, cautiously feel the wheel hub. If it’s too hot to comfortably keep your hand on it, the brakes are too tight and need re-adjustment. This heat can melt your wheel bearing grease and lead to bearing failure.

Brake Fluid

• It is poisonous and a powerful paint stripper. If you spill it, wash it off immediately with water. Do not rub it.
• It absorbs water (hygroscopic). It should be changed every two years to prevent rust inside your brake system.

Broken Brake Pipe

This is a critical failure. You can perform a temporary “bush fix” to get home.

1. Identify the broken pipe (it will be leaking fluid).
2. Fold the metal pipe over on itself and crimp it tightly with pliers or a vice grip to seal it.
3. This has sealed off that one brake. Your braking will be severely compromised (it will pull to one side), but you will have the other three.
4. You must bleed the system.

How to Bleed Brakes (Two-Person Method)

1. Fill the brake fluid reservoir to the top.
2. Person 1 (in cab): Pumps the brake pedal ~10 times and then holds it down firmly.
3. Person 2 (at wheel): Starting with the wheel furthest from the reservoir (e.g., rear-left on most trucks), loosens the brake bleed nipple. Fluid and air will spurt out.
4. Person 2: Tightens the nipple before Person 1 lifts their foot.
5. Repeat steps 2-4 at that same wheel until no more air bubbles come out.
6. Move to the next-furthest wheel (e.g., rear-right) and repeat the whole process.
7. Crucial: Check the reservoir constantly and keep it topped up. If it runs dry, you’ll suck air into the system and have to start all over.

3. Clutch System

Problem: You press the clutch pedal, and it collapses to the floor with no resistance.

Diagnosis: This is almost always a hydraulic failure (master or slave cylinder has failed, or you have a leak).

The Fix: You can still drive the vehicle.

1. With the engine off, put the vehicle in 2nd gear (or 1st if you’re on a hill).
2. Hold the key and start the vehicle in gear. It will lurch forward and start.
3. You must now change gear without a clutch (this is called “rev-matching”).
4. To change up, accelerate gently. Then, lift off the accelerator and, in that split second of “coast,” pull the gear lever into neutral, then into the next gear.
5. To change down, you do the same but will need to “blip” the throttle while in neutral to raise the engine RPM to match the lower gear.

4. Fuel System

Dirty Fuel

Avoid buying fuel from roadside containers. It’s often contaminated with water or paraffin. A water-separating filter funnel (like a “Mr. Funnel”) is a wise investment.

Symptoms: If the vehicle jerks or sputters under load, it often indicates a fuel supply problem or water in the fuel.

Petrol in a Diesel (or vice versa)

DO NOT START THE VEHICLE. DO NOT EVEN TURN THE KEY TO “ON.” This is a critical, engine-destroying mistake. The only solution is to drain the entire tank, flush the lines, and change all fuel filters.

Changing a Diesel Filter

1. Identify your fuel filter (and carry a spare!).
2. When you install the new filter, always fill it with clean diesel before putting it back. This minimises the amount of air you introduce.
3. Bleed the system. Any break in a diesel fuel line requires bleeding.

1. First, open the plastic wing nut at the base of the filter housing to drain any water. Let it run until clean diesel appears.
2. Find the manual primer pump (a button or plunger on top of the filter housing).
3. Loosen the “outlet” pipe or a bleed screw on the housing.
4. Pump the primer until diesel without any bubbles comes out of the loosened fitting.
5. Tighten the fitting and reconnect the pipe.
6. If it’s hard to start, have someone crank the engine while you pump the primer.

5. Cooling System

Overheating

If your temperature gauge suddenly climbs, your thermostat could be stuck closed.

Diagnosis: Cautiously feel the large radiator hoses (one inlet, one outlet). If one is very hot and the other is much cooler, the thermostat is not opening.

The Fix: Remove the thermostat. Your engine will take longer to warm up, but it will not overheat. This is a 100% safe temporary fix.

Refilling the System

1. After a repair, turn your cab heater on to its hottest setting. This opens the heater core, ensuring you bleed the entire system.
2. Run the engine with the radiator cap off.
3. Keep adding coolant/water as the engine warms up and the level drops (air is burped out).

Radiator Cap

This cap is designed to hold pressure. If the rubber ‘O’ ring is cracked or leaking, the system won’t pressurise, the boiling point will lower, and it will overheat. Always check it and carry a spare.

Leaking Radiator

Quick Fix: A “radiator sealant” product can plug small leaks.

Bush Fix: If you can see the specific tube in the radiator core that is leaking, you can clear the cooling fins around it, break the tube, and crimp both ends folded over to seal it off. You will lose a tiny bit of cooling capacity, but it will stop the leak.

Bush Mechanic FAQ

What daily checks should I do on a long dirt trip?

Do a morning/evening walk-around: tyres (pressure & damage), leaks, loose bolts, wiring chafe, brake lines, hitch, and suspension hardware. Listen for any new noises on the first 5 minutes of driving.

How do I choose wire size for accessories like a fridge?

Use thicker cable than you think—voltage drop kills fridge performance. For a rear-mounted 12V fridge, 8–10 AWG (8–6 mm²) to an Anderson plug with a clean earth to bare metal is a solid baseline.

Can I really drive home with a failed clutch?

Yes—start in gear and rev-match shifts as described above. It’s a limp-home technique only; plan short legs and avoid traffic.

Is radiator sealant safe to use?

For small leaks only, to get you out of the bush. Permanent repairs should follow. If you can see the leaking tube, the “break & crimp both ends” bush fix is often more reliable.

What brake fluid should I carry?

Match manufacturer spec (often DOT 4). Carry enough to bleed one corner fully. Replace fluid every two years because it absorbs water.

What’s the #1 spare that saves the most trips?

A quality puncture plug kit + compressor. Most trip-stoppers are tyres, and a plug gets you rolling fast.