TD42 engine: Your guide to the Nissan turbo diesel motor

Nissan’s TD42 engine as seen in the GQ and GU Patrols of the late 1980s and right up to 2007, was kind of the black sheep of the TD engine clan. But not in a bad way. While it shared the basic TD-family architecture in terms of cylinder spacing and construction materials, the TD42 was a six-cylinder engine in a four-cylinder family. Of course, that didn’t matter to Nissan Patrol buyers who quickly warmed to the engine for its never-say-die reliability and rugged construction.

With cast-iron block and cylinder head construction and measuring 4.2 litres, the TD42 was nothing out of the ordinary in that department. But instead of using a chain or a toothed rubber belt to drive the camshaft mounted in the block (the engine was an overhead-valve design) the TD42 used a series of gears to do that. It was definitely a bit out of the box, but it was a set-and-forget system that helped the TD42’s reputation as being some kind of bullet-proof. In fact, the TD42 soon gained a reputation for being a half-a-million-kilometre engine, provided you kept the servicing up to it. It wouldn’t be until 1990 – two years after the TD42 arrived – that Toyota would grace us with an engine of similar fortitude (and performance) in the legendary 1HZ.

We first saw the TD42 in the all-new GQ Patrol of 1988. This version was known as the Silvertop (for the colour of its rocker-cover) and it produced 85kW of power and 260Nm of torque. That doesn’t sound much and, to be honest, it wasn’t, but the engine’s ability to hang on, combined with the gearing in the lower ratios of the Patrol’s transfer-case gave it plenty of punch for off-roading which, in 1988, was still what vehicles like these were all about.

The GU version of the TD42 was known as "Blacktop".

There are, however, two distinct versions of that early TD42. It’s believed that in around 1994, Nissan revised the engine, probably to make it a bit cheaper to build. At that point, thinner, lighter pistons (and perhaps different gudgeon pins, the jury is out) were introduced and while the engine remained reliable if left untouched, it wasn’t so friendly towards aftermarket turbocharger kits (which had been a popular way of upping the performance). Plenty of owners found out the hard way that the later TD42 would crack pistons if you pumped too much boost into them.

Faced with the knowledge that the aftermarket was selling heaps of turbo kits to Patrol owners, Nissan got in on the act at a factory level for the GU patrol of 1997. While the normally-aspirated TD42 was still available, the factory turbocharged TD42T3 was also introduced, making 114kW and 330Nm of torque.

Known as the Blacktop (guess why) the GU version of the TD42 in both turbo and non-turbo form addressed those reliability shortcomings with even thicker pistons than the very first version, beefier con-rods and bigger gudgeon pins. In February 2003, Nissan gave the turbo version a little more love, fitting it with electronic control of the injector-pump timing, but pulling up short of making it an actual common-rail set-up. Power remained at 114kW but torque was well up at 360Nm, and this is generally regarded as the TD42’s finest hour. Like every TD42 sold here, it was only ever matched with a five-speed manual transmission.

Fuel consumption is not the TD42’s long suit, it should be said. It’s an old-school design and it’s toting around 2.5 tonnes worth of Patrol, so bank on between 12 and 14 litres per 100km on the highway and another couple of litres around town. Start using the boost on a turbocharged example or tow a camper-trailer or boat, and those numbers will climb dramatically.

In-service

The TD42 first appeared in the GQ Patrol and produced 85kW/260Nm.

The main reason the TD42 is so highly regarded by the hardcore off-roaders out there is that it’s a better chance than most to get you home every time. Even the allegedly lighter-piston version of the engine is fine provided you don’t mess with its tuning. Speaking of which, modifying the engine is when problems will start to appear. The trade reckons the bulk of the TD42’s perceived problems, namely a tendency to overheat when used hard, are all down to modified vehicles, usually those with aftermarket turbocharger kits.

Unless these kits include top quality components and are fitted and tuned by somebody who knows intimately what they’re doing, the result can be a Patrol that overheats when towing, off-roading or simply climbing a decent hill at highway speeds. By boosting the engine with a turbocharger, you also need to add more fuel to compensate for the extra air the turbo is shoving into the engine. That means a bigger bang (and more power and torque) but also more heat. The problem is exacerbated on vehicles with intercoolers as part of the turbo package, as these usually sit in front of the actual radiator, restricting air-flow and feeding already heated air into the cooling system.

The TD42 gained a reputation for being a half-a-million-kilometre engine.

The usual solution – and a lot of Patrols already have this fitted – is a bigger, aftermarket radiator. Again, quality is the key word here, and radiators remain one of those components where you’ll generally get exactly what you pay for.

But there are other causes of overheating, some of which may not seem too obvious at first. They include mounting driving lights in front of the grille. Again, this sounds trivial, but every square-centimetres of surface area is critical in keeping the TD42 cool, so partially blocking the radiator grille with lights is not a good idea. Modern, thinner LED driving lights have probably saved many a TD42 in recent years.

Taller diameter off-road tyres can also cause their share of problems in this regard. Really tall tyres can have a devastating effect on the vehicle’s overall gearing, making the engine work harder and requiring more throttle to maintain a given road speed. And that’s a recipe for more heat.

Read more Nissan Patrol advice:

- G60 Patrol: Your guide to the Nissan 4WD

- MQ Patrol: Your guide to the Nissan 4WD

- Series 4 Patrol: Your guide to the Nissan 4WD

- SWB Patrol: Your guide to the Nissan 4WD