When this 1995 Western Star 4964F Heritage model rolled off the production line in Kelowna B.C., Caterpillar‘s C15 engine was still on the drawing board. Time may have kept them apart initially; not any more.

Photo: A blast from the past still delivering a solid effort every month.

Two decades after its release the Cat‘s C15 still has an enviable following that‘s largely due the engine‘s proven reliability and performance. So much so that the C15 is a popular choice when it comes to repowering older trucks. Among the fleet of modern trucks operated by CR & S Jones of Scottsdale in Tasmania is a Western Star 4964F Heritage that‘s been repowered with a C15. The company transports timber products around the island and local ports for export to the mainland. The 4964F was purchased secondhand more than a decade and half ago, and has clocked up well over three million kilometres. In that time it has had a few modifications and updates and today its primary role in the fleet is the spare truck, although it‘s kept in top condition, ready to go to work whenever needed.

Back in 1995 when it arrived in Australia, it was powered by a Caterpillar 3406E rated at 339kW (455hp) at 2100rpm and developed 2237Nm (1650lb/ft) at 1200rpm. The transmission was an RTLO16718B 18-speed that delivered the power to a pair of Rockwell RT46-160 with a final drive ratio of 4.10:1, which rode on Hendrickson HAS400 air suspension. Today in 2019 the wick has been turned up a little since the C15 was slotted in under the hood where the old 3406E once resided. Power output has increased 75kW (100hp) to 410 kW (550hp) and torque increased by 271Nm (200lb/ ft) to 2508Nm (18509lb/ft) at 1200rpm. Needless to say, the transmission needed upgrading to handle the additional torque, and an RTLO20918B was bolted up to the C15. The Rockwell rear axles were retained, along with the 4.10:1 ratio that has the Heritage running at 100kph in the engine‘s sweet spot of 1650rpm.

Photo: The CAT C15 built on its predecessor‘s reputation for torque and longevity when it arrived on the scene in 1999.

Hendrickson HAS style suspensions are fine for light duty applications, but they are prone to axle tramp. Axle tramp is defined as an undesirable oscillation of the axle around the roll axis and reduces driveline universal life. This suspension is also susceptible to axle hang-up and loss of traction even when driving through driveways. Consequently, the Hendrickson was removed and was upgraded to an Airliner suspension to ensure the power was firmly planted on the ground. Commercial production of the Caterpillar C15 on-road engine commenced in 1999 and ceased in 2007. Rumour has it that the earlier engines with a 6NZ prefix in the serial number were the pick of the bunch. The C15 had a single turbocharger with simple electronics and weighed less than its predecessor the 3406E.

However, from a parts perspective there is good news; many components are interchangeable between the 3406E, C15, and ACERT engines. Nevertheless, there are subtle distinctions between each engine variant and it‘s well worth exploring the differences. Part of the design criteria for the C15 was to improve on the 3406E design and reduce oil leakage issues that plagued the older model. They achieved this with the introduction of relief slots in the bottom of the cylinder head that kept the head gaskets from getting crushed. However, many technicians have noted that it pays to use quality replacement head gaskets on the C15 to ensure no oil leaks.

But it wasn‘t all plain sailing for the C15. The transition to the next emissions standards meant Caterpillar built what became known as ‘Bridge‘ engines in the production year of 2002 to 2003, before the introduction of the C15 ACERT. These Bridge engines lacked the renowned performance of the original C15, experienced high exhaust temperatures, and suffered from terrible fuel economy. The good news story here is that ECM updates quickly rectified many of the issues. But don‘t let the nomenclature of the C15 ACERT fool you. For a long time, people thought the ACERT suffix to the C15 indicated the addition of the second turbocharger, but that is far from true. From a hardware point of view the ACERT engine has a one-piece steel piston as opposed to the C15‘s two-piece aluminium skirt piston design.

The stroke of the ACERT is the same as the C16 and there is an entirely new emission technology that ACERT draws its name from. Nevertheless, the good news is that when an engine has been on the market as long as the C15, there is a wide selection of quality aftermarket parts readily available that help improve the durability, performance and economy of the C15, e.g. pistons with graphite coating, rods and main bearings constructed from tri-metal blend, and induction hardened cylinder liners How does the C15 work out on the road? There was only one way to find out and that was to climb into the cabin for a week and do the job it was built to do. Day one was an early start, the big yellow engine under the hood cranked into life right on 3am. In the cool morning stillness, the turbo gulped in loads of chilled air; the result was astonishing torque as the Heritage climbed up and over the mountain range on the way south. Coupled behind, the curtainsider was stacked to the roof with new pallets; not the heaviest load, but a good load nonetheless.

Photo: Doesn’t get any more US 90’s than this.

Day two‘s assignment was a load of timber to the west coast of the island on a drop deck. Again, the C15 powered Heritage made light work of the load behind. For the rest of the week, the Heritage was connected to the walking floor chip liner, which had the gross weight up to 45.5 tonne, something for the C15 to really get its teeth into. The Airliner suspension upgrade gives the Heritage sure footing and that‘s something you need on the twisting undulating rural countryside of northern Tasmania. Performance-wise the C15 certainly has all 550 horses, and they‘re big-hearted Clydesdales too. The engine upgrade has given this old highway hauler a new lease of life. While the engine‘s performance and durability make it a sound investment, economy-wise the C15 can be a little thirsty if driven too hard, although if you let the big Cat do its thing you can achieve fuel economy that matches today‘s modern engines. Our economy for the first two days with the lighter loads and longer highway runs averaged 2.25km/l and on the heavy loads in the hilly country 1.8 to 1.9km/l, which included 30 minutes PTO time (per shift) operating the walking floor to unload.

When it comes to repowering an older truck with a C15, it‘s an easier task if the original engine was a CAT, because the engine mounts and wiring mean you can virtually drop the C15 straight in. On the other hand, if you‘re switching out a different engine, then be prepared to do a little more work to slot the C15 in. It‘s well worth talking to your accountant to discuss the best options to suit your particular business operation before rushing into the repower option, and do your homework on the warranty of the installation. New Zealand Trucking would like to thank CR and S Jones for their assistance compiling this article.

Photo: The Western Star is regularly called on to help with wood residue haulage that sees it at around 45.5 tonne…no sweat!