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4WD MODIFICATIONS - POWERTRAIN

REFURBISHING THE OLDER DIESEL ENGINE
There may be life in the old beast yet.

 

Older diesel powered 4WDs have a great deal of appeal for serious bush travellers. Pre-emissions engines have no electronics, no computers and no exhaust emissions after-treatment components.

 

All new turbo-diesels are electronically controlled and most have sophisticated common-rail-injection systems that can’t be bush repaired. However, the electronic diesel revolution has brought many benefits: better performance, improved economy, accurate fault diagnosis and engine protection from abuse being among them.

In the truck world, engine makers are well aware of the sensitive nature of most road freight and have 24-hour call-out availability for truck customers. A ‘vehicle broken down’ call prompts instant response from most engine makers. That’s not how it is in the 4WD world. Call your friendly 4WD dealer and suggest that he send out a breakdown vehicle to attend to a fuel system problem and see what sort of service you get.

To be fair, it’s not possible to have a service network that can cover all the places off-roaders go. Even it were a possibility the costs would probably exceed most travellers’ budgets. When you go seriously bush, you’re pretty much on your own.

Hence the appeal of the uncomplicated diesel.

 

 

Modernising an Oldie

 

Whether you have an older, naturally aspirated diesel 4WD, or you’re considering buying one, the refurbishing exercise is the same.

A well-serviced diesel – that’s an oil drain every 5000 kilometres and filters every 10,000 since new – should last around 500,000 kilometres before needing rebuilding. A naturally aspirated diesel in good nick should have strong oil pressure and little oil consumption.

If the subject of your attentions doesn’t meet these conditions it’ll need a rebuild before you do anything adventurous with it.

Pre-emissions diesels are still around in the used market, powering 1990s 4WDs and these vehicles have particular appeal for serious off-roaders, who don’t want the complication of high-pressure fuel injection systems and multiple emissions-reducing after-treatment components – EGRs, diesel oxidation catalysts (DOCs), DPFs and selective catalytic reducers (SCRs) that need an AdBlue tank.

The most popular older diesels power Nissan Patrols, Toyota LandCruisers and HiLuxes that dominated the 1990s market. Early examples were naturally aspirated, but by the late-1990s, all were factory turbocharged.

Refurbishing one of the factory turbo engines is pretty straightforward, unless you’re after more grunt than the standard engine produced. Then you could run into problems that include overheating – especially Patrols – cracked pistons and bent conrods.

High-mileage engines – anything over 500,000km – really should be completely rebuilt, with new or rebored liners, new pistons, new conrods, recon or new cylinder head, camshaft and valves.

Refurbishing one of the naturally aspirated engines is also straightforward, if you’re content with spending a lot of money and finishing up with a poorly performing – by modern standards – 4WD. Most rebuilt naturally aspirated diesels are fitted with after-market turbochargers by their owners and the standard naturally aspirated engine components mostly aren’t up to that.

Turbo’ing an engine that wasn’t designed for increased combustion heat and pressure is a risky business and how risky is what we set out to discover with our own 1993 LandCruiser 75 Series ute. We expected trouble and we got it.

We’d bought the vehicle second-hand – two previous owners – in 2010, with 320,000km on the clock and were told that the engine had been rebuilt at 200,000km. That seemed odd, until we later discovered hints that it had been turbo’ed at some stage. Mods to the heater hoses and an extractor exhaust manifold pointed to a removed turbo and cheaper exhaust headers than a genuine Toyota exhaust manifold.

With our slide-on camper on board, Harry the 75 Series was a slug on the highway, so we decided to fit a turbo. Experienced people warned us about likely engine drama, but we fitted a pyrometer, to monitor exhaust gas temperature and took a punt.

Complicating things a little was short period of engine ‘dusting’, caused by an ill-fitting air cleaner gasket , plus a slight oil leak at the back of the cylinder head.

Performance was greatly enhanced by the turbo and, for around 100,000km of on and off road tripping, there were no obvious issues. Then we noticed that the head oil leak had accelerated and there were small flecks of oil in the coolant. “Troooble at mill.”

 

 

A subsequent tear-down showed a cracked cylinder head, some piston-top deterioration and scored bores and bearings. Some of this may have been pre-existing from the original turbo fitment and the dusting episode may have contributed to the bearing wear.

We checked our options that included selling the ute as it sat, but where would we get a stretched wheelbase, GVM-upgraded equivalent? Second hand factory-turbo, 1HD-T engines were available as replacements, but with ‘driveway’ warranty. One of our mates went down that route, but when the engine pooed itself six months later, he was up for a full rebuild – a total $30 grand exercise, including the engine purchase.

So, we figured the safest route, at the half-million-kilometre mark, was a thorough engine rebuild that would take into account the additional stress of turbocharging. At least that way, we’d know what we’d paid for. 

Our regular servicing shop – AJ Automotive Services Bowral (NSW) – engaged Southern Engine Reconditioning, of Kembla Grange (NSW), to do the job. This highly professional outfit rebuilds engines up to 12-cylinder earthmoving gear size and puts a 12-month, unlimited-kilometre warranty on its work. However, if you’re looking for ‘cheap’, go elsewhere.

SER has plenty of experience with rebuilding Patrol and LandCruiser engines for turbocharging and they know exactly what components need upgrading over the standard bits.

 

Block pre-bored requiring sleeve due to cracked head corrosion

 

The only surviving 1HZ component was the block that was completely refurbished. After boring, one of the cylinder liners showed corrosion at the top, where the cracked head had been leaking coolant into the cylinder.

 

Block bored-out with a step to take a semi-finished sleeve

 

 

Semi-finished sleeve being trimmed-down before being decked

 

It was professionally machined to create an overbore with a bottom step for a new liner insert, after which the refurbished block was ‘decked’.

 

Block being decked after being sleeved and bored

 

Testing showed that the crankshaft had a small crack, so it was junked and the head, camshaft, valve gear, pistons and conrods were scrapped. 

 

Replacement rods have much bigger little ends than standard

 

The replacement pistons had much bigger gudgeon pins and ceramic-coated tops. A brand new crank, head, camshaft and valve gear went on, along with a new injection pump and injectors. A replacement timing case incorporated a higher-capacity oil pump.

 

 

We popped into the shop a couple of times during the operation and were impressed with SER’s attention to detail. New, heavier-duty conrods were being fitted, but only after a thorough balance check of big and little ends.

 

 

The standard tolerance was + or – 2.5 grams, but SER’s star engine builder was happy only when all rod weight measurements were exactly the same.

 

 

Turnaround time was around one month, before the rebuilt engine went into Harry. In the meantime, AJs had fitted a brand new copper radiator and all engine bay hoses, including normally tricky-to-access power steering plumbing. The flywheel was machined, of course and mated to a new heavy-duty clutch.

 

 

It’s early days for an assessment, but the rebuilt engine is quieter across the rev range and is much, much smoother. In the running-in phase, in late 2022, it’s way too early for a performance comparison, but we’ll publish that in late 2023.

 

 

Turbocharged HiLux

 

We followed a late-90s HiLux through an updating process, carried out by ARB Elizabeth, SA.

The HiLux in question had travelled 250,000 mainly on-road kilometres and had been regularly serviced, but the engine had been turbocharged after its original warranty expired and the owner reported recent poor performance, increasing fuel consumption and obvious black smoke from the exhaust.

Brad Newham, ARB Elizabeth’s principal, inspected the HiLux and had his boys do a health check on the 2.8-litre.

The owner knew that the old turbo had not been ideal, right from the start, and Brad explained to him that it looked too large for correct matching to the Toyota four – more like a turbo for a four-litre. The old turbo was also showing signs of bearing wear, with traces of oil in the turbine section.

Fortunately, the local Toyota dealer had a ‘long engine’ – assembled block and head without ancillaries – on the shelf and this engine also featured later-edition pistons and rods.

The decision was made to fit this engine and kit it up with a new DTS turbo, correctly sized for the 2.8-litre diesel and offering water cooling, which the previous one did not.

The pump and injectors were dispatched overnight to Rankin Diesel Injection Services, in Melbourne, where it was discovered that the injection system had ingested some bad fuel, causing excessive wear and seizing of some components. The pump and injectors were completely overhauled and the pump was fitted with a boost compensator.

Boost compensators are necessary, Geoff Rankin insisted, to ensure that the fuel supply from the mechanical pump matched the boost from the turbo. Without a compensator the air: fuel ratio can stray far from the ideal 20-23:1 – as rich as 17:1 and as lean as 30:1.

The rebuilt pump and boost compensator were bench tested for accurate fuel metering before going back to ARB Elizabeth.

turbo'd engine While the injection system was being rebuilt the boys bolted on the new DTS turbo. With the pump and squirters back in the HiLux it was time for a trip back to the dyno.

The results justified the time and expense: rear wheel power went to 53.9kW (typically only 45kW on naturally aspirated engines) and rear axle torque increased from a naturally aspirated 2000N to a peak of 3000N. (Note that these torque figures are engine torque multiplied by the rear axle ratio.)

The power and torque curves across the entire rev range were much ‘fatter’ than standard, indicating much more performance and flexibility.

Turbo performance sometimes comes at the expense of engine durability, so the dyno equipment was used to measure boost pressure – limited to 10psi – and exhaust gas temperature at the manifold. The dyno showed a top exhaust gas reading of just under 500C.

The dyno figures were borne out on the highway, where the owner reported greatly improved acceleration and flexibility in top gear. Oil pressure and coolant temperature readings remained at previous levels.

Fuel consumption benefits are possible with a turbo conversion, but in this case consumption remained at previous levels – around 11L/100 km – probably because the owner was using and enjoying the HiLux’s considerable extra urge!

 

Cooling System Upgrade

The extra urge provided by the correctly matched turbo soon showed a weakness in the HiLux’s cooling package. The gauge climbed on steep grades, particularly if the engine was left to lug around peak torque revs.

The cure was simple enough: rebuild the cooling system. The water pump was replaced, along with the 10-year-old radiator and all the hoses and belts. The thermostat was replaced by a high-flow design.

The viscous fan lacked resistance when turned by hand, so a new hub was fitted.

All good!

We followed the bush-travel career of this HiLux and last time we heard it was still going strong – some 250,000km later.

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