Mazda BT-50 Problems

Assuming your car is fitted with a manual transmission, this could be as simple as a gearshift linkage that has jumped ship, or a selector cable that has stretched or snapped. If that’s the case, you should be able to look from underneath the car to see what’s hanging off or missing and not connecting the shifter to the actual gearbox. If the shifter moves freely inside the cabin, but doesn’t sound or feel like it’s connected to anything, that’s probably the case.

If you’re unlucky, you may find that there’s something inside the transmission (probably to do with the selector mechanism) that has broken, worn out or failed. In that case, you need to go inside the transmission to see what’s what, and that’s a much more complex task that involves removing the transmission from the car and lots of labour.

The automatic transmission is a mysterious, marvellous piece of equipment that manages to work almost in spite of its complexity. Guessing at a problem like this is fraught with danger, so the best advice is to get the vehicle to a transmission specialist, download the fault codes and see if they give the technician any hints as to what’s up.

Transmission problems with this make and model are hardly unknown, so avoid driving the vehicle any farther until it’s been looked at. You may end up doing more damage by continuing to drive it.

The actual problem could be anything from a transmission that is about to catastrophically fail, to one that has simply lost its 'memory' or programming and can be rebooted fairly easily and quickly.

For a start, this model Mazda BT-50 did have a recall to check the transmission’s output shaft speed sensor. If this failed, the transmission could suddenly shift back to first gear which, if it did so at highway speeds, would have been potentially disastrous. But it’s also possible that this sensor could fail and not allow the transmission to shift beyond first gear, so that would be worth a check. A transmission specialist is your best bet here.

Beyond that, simply servicing a component won’t generally fix a fundamental problem. It would be the same with a worn out or internally damaged engine; servicing that engine with fresh oil and spark plugs will not fix the underlying condition.

The problem of a clutch pedal hitting the floor without actually disengaging the clutch is usually caused by either a faulty clutch master cylinder, slave cylinder or a loss of clutch fluid from the system.

These are not expensive or complex things to fix and new master cylinders and slave cylinder are readily available from parts stores and online sellers. However, if the problem is a lack of hydraulic fluid, you also need to figure out where the old fluid went. There must be a leak somewhere and until that’s fixed, topping up the fluid will only be a temporary fix.

If you’re really unlucky, you might find the clutch has collapsed internally, at which point a whole new clutch will be needed. This vehicle also used a dual-mass flywheel, so you’ll often need to replace that as well to do the job properly.

The EGR system is an important part of any modern turbo-diesel’s emissions control package. So if it’s not working properly, or telling the on-board camera that it has a problem, the computer may presume the problem is serious enough to not start the engine to avoid further damage.

You need to go back through your work, checking and double checking that each wire, sensor and fastener is properly fitted and secure. You may also need to check the EGR valve itself to make sure it hasn’t been damaged in the cleaning process. The on-board computer may need a reset after this procedure, so a visit to a diesel specialist might be the best next step.

Conventional wisdom says the first place to start looking is the turbocharger and its plumbing. A turbocharger operates at very high speeds and a whistling noise is quite common. What you shouldn’t have, however, is a loud version of that noise, or a whistle that is suddenly louder than ever before.

Cracked or leaking turbo-plumbing can allow the noise to escape, but a turbocharger with a worn bearing can also suddenly become louder in its operation. So that’s where to start looking.

Why does the noise drop in the higher gears? Perhaps because you’re cruising in those gears and not accelerating hard as you do in the lower gears. Less throttle input means a slower turbocharger speed and a drop in turbo volume and pitch.

Sometimes head units need a reboot or a return-to-factory-settings button to be pressed. Often, there will be a tiny hole somewhere on the face of the head unit. Into this, you insert a thin piece of wire or a toothpick (or similar) and press just hard enough for the screen to go blank and the unit to reboot. It sounds like you’re using the factory Mazda reversing camera with an aftermarket head unit, so you may need to visit a car audio specialist to get it all working together.

Changing a car’s battery can often be enough to scramble the settings on things like cameras and stereos. You may need to find the security code for the head unit to make it all work properly, too.

You might be looking at two distinct issues here. The high idle could be caused by any number of things including a dirty intake system, or something electronic. It could simply be that the idle was set too high the last time the vehicle was serviced.

This may be contributing to the feeling of the engine shuddering when you switch it off, but in reality, a lot of diesel engines exhibit this. It’s all to do with the heavy-duty nature of the diesel engine design. Because of the high combustion chamber pressures inherent in the diesel’s design, the whole thing needs to be more physically robust than a petrol engine of the same size and capacity. That means everything from the crankshaft to the con-rods, pistons and even the cylinder head and crankcase need to be made stronger. And that means more material and that means more mass.

This is why diesels generally don’t rev as high as petrol engines (there’s much more reciprocating mass) and why they can feel a bit lumpy when you load them up and even at idle. So, when you switch one off, it can feel like it’s trying to jump out of the engine bay. However, if this sensation has become more pronounced over the years, it might be wise to check the engine and transmission mounts for wear. Any wear or looseness here can contribute massively to vibrations from the driveline being passed through to the cabin.

A trip to your local transmission specialist is the first step here, and don’t even think about driving the vehicle father than that. You could easily do more damage than is already existing. Modern automatic transmissions are incredibly complex things and there’s a lot that can go wrong.

You might be lucky and simply have a low transmission fluid level (although you’ll still need to find and fix the cause of the leak). But, equally, you may have a transmission that is literally on its last legs. The problem is that all these symptoms can show up through all sorts of transmission woes.

Either way, a specialist workshop should be able to diagnose the problem and work from there.

I’d start by talking to a transmission specialist. There’s a fair chance they will have seen these exact symptoms before in this make and model and will know what’s wrong without wasting any time or money on guesswork. It’s probably also worth going back to basics and checking the transmission fluid level, as low fluid can cause all sorts of drive problems. If, on the other hand, the gearbox is worn out internally, you’ll either need to rebuild or replace it, but don’t rule out something less expensive like an internal selector fault or even a torque converter problem.