The CJ340 rewards routine maintenance more than almost any other classic 4x4. Nothing on it is complicated, but everything on it is old — and most of the expensive failures owners write about trace back to a missed filter change, old fluid or a brake adjustment that nobody did.
This guide sets out a practical service schedule, explains what oil and fluids to use, and points to the manuals worth owning. Original Mahindra service intervals are hard to find today, so the schedule below is a conservative owner-practice baseline for a thirty-year-old diesel. Where you have the factory manual, its figures take priority.
The schedule at a glance
Intervals are shown by distance or time, whichever comes first. Many CJ340s cover few kilometres a year, and on a jeep like that, time matters more than distance: oil, fuel and brake fluid all age while the vehicle stands.
| Every fill-up / weekly | Oil level, coolant level, tyre pressures, look underneath for leaks |
|---|---|
| Monthly | Drain the water separator (if fitted), check brake fluid level, battery terminals |
| 5,000 km or 6 months | Engine oil and filter, grease chassis and steering points, adjust brake shoes, check fan belt |
| 10,000 km or 12 months | Fuel filter (bleed after), clean or replace air filter, check gearbox, transfer case and axle oil levels, inspect hoses |
| 20,000 km or 2 years | Valve clearances, brake fluid change, coolant change, glow plug test before winter |
| 40,000 km or 4 years | Gearbox, transfer case and axle oil change; injection timing and injector check if behaviour has changed |
What oil for a Mahindra CJ340
The Peugeot XDP 4.90 is an indirect-injection diesel from an era before modern low-viscosity oils. Use a diesel-rated engine oil; most owners run a 15W-40 mineral or semi-synthetic diesel oil, which suits the engine's clearances and copes with the soot an old diesel produces. Check the grade against your manual and your climate — a hot Australian summer and an Alpine winter have different needs.
Change oil on time even if the jeep barely moves. Short trips and long idling — gate-opening on a farm, or warming up on a winter morning — load the oil with moisture and fuel, which is harder on the engine than steady driving.
For the KMT90 gearbox, T18 transfer case and the axles, use the gear oils specified in the manual, and check levels at every second oil change. Leaking seals on old gearboxes are common; a low oil level found early is a seal, found late it is a gearbox rebuild. See our KMT90 and T18 guides.
Fuel system
Water and dirt are what kill mechanical injection pumps. Drain the water separator regularly, replace the fuel filter at least once a year, and bleed the system every time a filter is changed. If the jeep sits for months, keep the tank full to reduce condensation and consider a biocide treatment.
Our injection pump guide and cold start guide explain what happens when this is neglected.
Cooling system
Change the coolant every two years, using an antifreeze suitable for older engines at the concentration your climate needs, and do not mix different coolant types. Old coolant loses its corrosion protection and starts eating the water passages and head gasket sealing faces.
Keep the radiator clean inside and out, replace hoses that feel soft or cracked, and never remove the thermostat to cure overheating — that hides the fault and makes the engine run cold and wear faster. See our overheating guide and head gasket guide.
Brakes
The drums do not self-adjust, so adjust the shoes at every oil change. It takes half an hour and is the single biggest improvement most owners can make to how the jeep stops.
Change the brake fluid every two years. Pull the drums once a year to check the linings and look behind the wheel cylinder dust boots for leaks. Full details in our drum brake guide and master cylinder and bleeding guide.
Steering, suspension and greasing
Grease every nipple on the chassis at each oil change: spring shackles and pins, propshaft universal joints and slip joints, and steering joints. Dry shackles wear quickly and make the ride and handling worse; dry universal joints fail without much warning.
Check the steering knuckle seals for leaks and the steering box for play and oil level. Some play in the steering box is adjustable; see our steering box guide. Inspect leaf springs for broken leaves and worn bushes, covered in our leaf spring guide.
Electrical and starting
Clean battery terminals and the main earth straps once a year — most CJ340 electrical faults are bad earths. Check charging voltage with the engine running. Test the glow plugs before each winter. Our electrical and charging guide covers the wiring and the stop solenoid.
Service manuals and documentation
A genuine Mahindra CJ340 workshop manual is the ideal reference but is hard to find; owners trade scanned copies through the communities listed in our forums and community guide. A Mahindra parts catalogue is almost as useful, because its exploded diagrams show how assemblies go together and give part numbers.
For the engine, workshop manuals covering the Peugeot XD/XDP diesel family are the best available reference, since the XDP 4.90 was also used in Peugeot vehicles. For the chassis, body and many running gear items, Willys CJ-3B manuals are relevant thanks to the shared design — see our parts interchange guide.
Keep a service log: date, odometer, what was done and which parts were fitted. It helps with diagnosis, supports classic registration in countries that ask for history, and adds value when you sell.
Frequently asked questions
How often should I change the oil in a CJ340?
Every 5,000 km or six months, whichever comes first, as a conservative baseline. Jeeps that do short trips or long idling benefit most from sticking to the time interval.
What oil does a Mahindra CJ340 use?
A diesel-rated engine oil. Most owners use 15W-40 mineral or semi-synthetic diesel oil for the Peugeot XDP 4.90; check your manual and climate.
Where can I find a CJ340 service manual?
Genuine Mahindra manuals are rare; owner communities share scanned copies. Peugeot XD/XDP diesel manuals cover the engine, and Willys CJ-3B manuals cover much of the chassis.
What is the most neglected CJ340 maintenance job?
Brake shoe adjustment. The drums do not self-adjust, so adjust them at every oil change.
Keep yours on the road
OEM and reconditioned CJ340 parts ship worldwide. Explore the fan site, regional guides, and owner community.