Mazda BT-50 Engine Problems

It mightn’t seem like the vehicle is struggling, but when you consider that a caravan of this size can easily weight the best part of three tonnes, you can see how it puts a strain on every component of the vehicle towing it. It sometimes only takes a small hill or a headwind to push a towing vehicle into its discomfort zone. Do that long enough and eventually something will get hot enough to trigger the limp-home response.

But don’t rule out a check-up at a BT-50 or Ford Ranger (they’re the same vehicle under the skin) specialist who should be able to pinpoint the weak link, as well as offer solutions to stop it happening again. You might find you need a bigger transmission or engine oil cooler, or even a retune of the engine to bring it back to tip-top shape.

Accessories you’ve added can also make a difference. Have you, for instance, fitted a roof rack or larger wheels and tyres? A roof rack can add a lot of aero drag that has to be overcome, while bigger tyres can mess up the vehicle’s gearing, causing it to work harder for the same road speed as before.

A powertrain warning light can be triggered for literally hundreds of reasons. So there’s no point trying to guess what’s wrong here. Instead, have the vehicle electronically scanned at a workshop and see if the on-board computer can shed any light on what components or systems are at fault.

Theoretically, the computer should have logged the cause each time the warning light has flashed on. During a scan, these faults will show up as a series of fault codes which the mechanic will be able to decipher to get a good idea of what’s wrong. Without this information, you could be chasing up blind alleys for weeks and months.

The other thing you can do is make a note of what the vehicle is doing when the light comes on. For instance, if the warning light flicks on when you’re towing, you may have a driveline overheating issue.

There’s a very simple check you can do to see whether the battery or the charging system (alternator, regulator and wiring) is at fault here. With the engine running, place the probes of a multi-meter (switched to measure voltage) on the relevant battery terminals. If you see a figure of anywhere between 13.2 and 14.7 volts, the charging system is doing its job. You might need to rev the engine slightly off idle to see these numbers, but the voltage going into the battery should be in that range.

At this point, the battery becomes the main suspect, and a worn out battery will often neither hold a charge nor accept one.

An open circuit on a fuel injector is usually caused by either a broken wire to the injector, a loose terminal somewhere in the electrical circuit that drives the injector or a burned-out coil in the injector itself.

Changing the suspect injector will tell you if the coil is the problem, but if that doesn’t fix it, you’ve got to work backwards from the injector until you find the fault. Bear in mind that if the injector itself is at fault, the other three injectors might be ready to go out in sympathy. Modern common-rail engines can be hard on injectors and they sometimes need replacing before they’ve done 100,000km.

This sounds more like a gearbox that isn’t selecting fifth gear properly, rather than one where it’s leaping out of fifth. For it to pop out of gear when cruising along suggests it’s not getting into gear fully in the first place. You might be able to adjust the shifter’s position and alignment and therefore get fifth gear to engage more fully.

There’s also a chance that this refusal to select fifth gear is the result of bent or worn selector forks within the transmission itself, and that’s a gearbox-out job unfortunately. So the first step is to get underneath with a torch while somebody inside attempts to select fifth gear. If the selector linkage runs out of range of motion, you might just have an adjustment problem which can be pretty easily sorted.

On the surface, you’d probably start looking at the car’s fuel system. A diesel, even a modern one, is controlled largely by how much fuel is being pumped into it and at what pressure. If the fuel pump is slack or the injectors, filters or lines are faulty or leaking, you might find that there’s simply not enough fuel to keep it revving on beyond that 2200rpm.

But you could also be looking at an exhaust problem, a partially blocked intake system, dirty air filter, or even a worn out turbocharger. A mechanic who is familiar with this make and model is going to have the best chance of diagnosing what’s wrong. Chances are yours is not the first vehicle to do this, and a specialist mechanic has possibly seen it all before.

The fact that the fuel economy average seems to be creeping up can have a lot to do with the fact that you’re becoming more familiar with the vehicle and using more throttle as a result. But remember, too, that until you reset the average on the trip computer, what you’re seeing is the full history of your consumption from when the trip computer was last zeroed, not just the most recent trip you’ve done.

It's true that engines often start to use a little less fuel as they 'bed in’ after a few thousand kilometres. And for a modern turbo-diesel like yours, I reckon 10,000km or even 15,000km might be the magic number. However, don’t be too disappointed if it doesn’t come down a whole lot. I reckon for that vehicle, driven the way you’ve described, 10 or 11 litres per 100km isn’t a bad average to aim for.

Other factors play a big part, too. Does the vehicle have a bull-bar or roof racks? Both these add weight and aerodynamic drag respectively, and can easily make the car consume more fuel. A roof rack at 100km/h can be worth an extra litre per 100km.

Rather than the steering completely locking up, it’s more likely you’re feeling steering that has lost is power-assistance. It can make the wheel extremely heavy and could feel as though the car won’t steer at all. This is linked to the engine stalling, because the power-steering on this vehicle is driven by a belt from the engine. No engine means no power-assistance.

The other questions, of course, are why is the engine stalling and why only on left-hand turns. There are plenty of things that can cause a modern engine to stall from a dirty fuel filter to a blocked injector or an electronic fault. And about a million things in between. An electronic scan of the vehicle might throw up a fault code that will help a mechanic unravel what’s going on.

There are many reasons for a vehicle to enter limp-home mode. One of them, of course is transmission temperature, but there are lots of things being monitored, from the temperature of the engine oil, coolant temperature, oil level and even the operating temperature of the EGR valve (which is often water-cooled in vehicles like the Mazda).

The point being that even though the transmission entered limp-home mode, the actual problem may have been elsewhere, but the vehicle’s computer believed that shutting down much of the transmission’s functions would preserve and protect the rest of the driveline. Don’t forget, either, that there are many things – a failed solenoid, low fluid level, even a faulty wiring connection or earth – that can cause a transmission limp-home event beyond actual overheating.

This is a really common problem with this model (and the Ford Ranger with which it shared its mechanicals). Many buyers avoid this model for this very reason. Even though many fixes have been tried it seems that this car, shown a hill and a hot day, will often overheat.

Several theories exist including that the EGR valve is the problem, as it fails and allows coolant to escape (usually into the engine cylinders). But even when the EGR valve is working properly, this engine is prone to running too hot. Some other theories hold that the thermal management of the engine itself was just underdone and there’s no real fix for it. That’s borne out by the number of people who have tried different radiators, thermostats and cooling fans and still have a vehicle that overheats.

But you could try reverse flushing the radiator and making sure than every part of the cooling system is working efficiently and properly. That will maximise your chances of not having the engine overheat but, in this case, there are no promises.