A set of ZD30 CRD injectors is a four-figure bill. A diesel pre-filter is a couple of hundred dollars and an hour on the hoist. That maths is why we talk every common-rail Patrol owner into one, and why we fit them to most TD42s that go anywhere remote.
What the factory filter doesn't do
The factory Patrol fuel filter is a fine particle filter. It does that job well. What it doesn't do well is separate water, and water is what kills a diesel fuel system in Australia. Servo tanks in regional areas carry water from condensation, jerry cans pick it up, and the Patrol's own tank breathes humid air every night. Water past a common-rail injector tip erodes the nozzle and scores the pump; past a TD42 rotary pump it rusts the internals.
A pre-filter sits before the factory filter and does two jobs: it spins the water out and holds it in a bowl you can drain, and it catches the coarse rubbish so the fine factory filter lasts.
Micron ratings, properly
The pre-filter should be coarser than the main filter, not finer. A 30-micron pre-filter with a water separator ahead of the factory 2 to 5-micron filter is the right arrangement. Put a 2-micron filter in the pre-filter position and you've got two fine filters in series, double the restriction, and on a CRD that means low rail pressure, limp mode and a lift pump that works itself to death.
ZD30 CRD
This is the engine that needs it most. Common-rail injectors run at pressures that turn a droplet of water into something that pits steel. The factory filter has a water-in-fuel sensor, but it warns after the water has arrived, not before. We mount the pre-filter on the chassis rail ahead of the factory filter, plumb it with proper diesel-rated hose and fittings, and extend the drain so you can empty the bowl without lying under the ute.
ZD30 DI and TD42
The DI and the TD42 use mechanical injection and are more tolerant, but a rotary pump that's ingested water is a $2,000 rebuild, and in the TD42's case the pump is the part that's getting hard to find new. If you tow a van through the outback or run off jerry cans, fit one.
Where it goes and how we fit it
Chassis rail, upstream of the OEM filter, below the tank outlet height so it gravity-primes, above the lowest crossmember so a rock doesn't take it out. Diesel-rated hose only, double clamps, and a hand primer if the model doesn't have one on the main filter (makes a filter change a five-minute job). On a GU we usually mount near the factory filter location on the inner guard or rail so the lines stay short.
We fit water-separating pre-filter kits matched to the model, and we'll fit a customer-supplied kit as long as it's a water-separating unit rather than a second fine filter.
Servicing it
Drain the bowl at every oil change and after any dodgy fuel. If there's water in the bowl more than once, find the source; it's usually a jerry can. Change the pre-filter element at 20,000 km, or sooner if the Patrol starts to hesitate under load, which on a CRD is the first sign of restriction. Keep a spare element in the glovebox on long trips; it's the one filter you can change on the side of the road.
Signs you already needed one
A factory fuel filter that blocks early. A CRD that stumbles on hills after a regional fill-up. A water-in-fuel light. Rust in the factory filter when it's cut open. Any of those and the pre-filter is late, not early.
Fitting takes about an hour in Burleigh Heads. Ring 07 3924 3317 or book online and we'll do it with your next service.
