Mazda 3 Engine Problems

It all depends of what sort of a leak we’re talking about here. If the tank is constantly leaking after it’s been filled up, there’s clearly some sort of hole somewhere in the tank or its plumbing from the filler neck to the tank proper. You could surmise that the level of fuel in the tank at which the leak stops, is also the level of the hole or crack. As the fuel drains further (as you drive the car) the fuel level is below that of the leak-point and the leak stops. Either way, this is a dangerous situation as even if there’s no liquid fuel leaking, there’s almost certainly fuel vapour escaping (which is more flammable than petrol itself).

While it’s rare for a tank to fail, much more common is having the plumbing which takes the fuel from the filler neck to the tank cause a leak. But if the leak stops soon after you’ve filled up, it could simply be that a small amount of fuel has sloshed out of the filler neck and into the car’s body near the neck, where it can drain away, thanks to gravity, towards the bottom of the car where you’re seeing it. Next time you fill up, be sure not to overfill the tank and remember to use the watering can on hand to slosh away any spilled or excess fuel.

That’s not a bad innings for a four-cylinder engine, even a modern one (although I’ve seen similar engines with more kilometres and still going strong). There’s a fair chance the piston rings and valve stem seals have lost some of their mojo and are allowing the oil to be burned in the engine. It’s normal wear and tear, but it needs to be fixed on the basis of the pollution being produced from the tailpipe. Also, eventually, something major will fail spectacularly and leave you stranded.

Your options include rebuilding the current engine or finding a second-hand engine with fewer kilometres on board and simply swapping it into your car. Thanks to the fact that the Mazda 3 was a popular car with younger drivers, they’re somewhat over-represented in wrecking yards, often with engines in very good condition. This would certainly be cheaper than rebuilding your current engine.

Many diesel engines don't appreciate being run out of fuel and will exhibit this behaviour if you allow them to run dry. That's because a lot of diesels have a fuel system that doesn't automatically prime itself and start pumping fuel once it's run dry.

As a result, some diesel cars have a hand primer under the bonnet that allows you to prime the diesel fuel pump and get going again. But modern ones like your Mazda often don't, and priming them involves a specific procedure to get the fresh fuel from the tank to the engine. Most workshops will be able to carry out this job for you, but simply continuing to crank the engine with your fingers crossed will do nothing more than flatten the battery.

Cars have never been more dependent on their electrical systems than they are today. Sometimes, changing a dead battery can lead to the sorts of problems you've noted, and while it could be something more mechanical, there's one thing you can try at home before phoning the mechanic.

Disconnect the battery and leave the car for at least half an hour. Then, reconnect it, start the engine and go for a drive of at least 30 minutes. That will usually be enough to perform what's called a reset and may solve your problems.

If not, you need to have the car scanned at a workshop to see what problems the on-board computer has identified.

The Mazda 3 timing belt or chain question is a common one, but one with a fairly simple answer. Unless the Mazda 3 in question is the very first turbo-diesel model (sold in Australia between 2007 and 2009) then the engine powering it uses a timing chain rather than a rubber belt.

The exception was the 2.0-lire turbo-diesel which used a rubber, toothed timing belt. The design seems sound, however, and Mazda’s recommended replacement interval for the belt and its tensioner is every 120,000km. Make sure this has been carried out promptly, as a snapped belt will probably destroy the engine. A small sticker somewhere in the engine bay should record the most recent belt change. The complete kit to replace the timing belt on this engine is available for around $200 and you should budget another few hundred dollars to have the job carried out by a workshop. Best practice is to also change the water pump and thermostat at the same time as these live in the same area of the engine.

The task of the timing chain or timing belt is exactly the same: They take drive from the engine’s crankshaft to the camshaft and, in the process, keep all the moving parts in harmony. Many car makers moved away from a timing chain to the rubber, toothed drive belt as a way of simplifying engine design and driving down the cost of each engine. The rubber timing belt is also quieter in its operation and is also less prone to stretching (as a timing chain can) so the camshaft (commonly referred to as the cam) stays in perfect synch with the rest of the engine’s rotating parts. The rubber belt is a simpler design because it doesn’t need to be tensioned via oil pressure from the engine as many timing chain systems are.

The timing chain, meanwhile, is preferred by some manufacturers because it should last the lifetime of the engine and never need replacement. This isn’t always the case, however, and some engines designs from a variety of manufacturers suffer problems in this regard. But, in a properly maintained engine of sound design, the timing chain should never need attention, while the rubber timing belt generally has a replacement interval of between 60,000km and 120,000km, depending on make and model.

It has a chain, so there’s no regular maintenance required. The only reason you might replace the chain is if it were to wear.

The engine is most likely overheating, even though the gauge is at zero. Check the coolant level, and for leaks from the radiator or hoses. It could also be a blown head gasket. The bottom line is it needs investigation by a mechanic.

Yes! No! Quite possibly! The largest factor in achieving good fuel efficiency is the nut behind the wheel (the driver). If you drive with efficiency in mind you will find Mazda's sales-dominating compact car will be able to travel hundreds of kilometres between refills, averaging approximately 5.7L per-100km for the 2.0-litre engines and approximately 6.5L per-100km for the 2.5-litre engines.

Drive the car gently for 10 minutes to get the oil warm. Park the car on level ground, lift the bonnet and loosen the oil filler cap on the engine, and slide a tray or pan with at least 5-litres of capacity under the car. There is a flap held on by a couple of plastic screws protecting the drain plug and oil filter. You may not be able to reach the drain plug on the sump underneath the car without lifting the vehicle. If this is the case remember to use multiple chassis stands to securely hold the car in the air, and to ensure the car is as level as possible (so you might need to jack up the rear of the car to keep it flat). After 10 minutes the oil should have stopped dripping from the sump plug so put it back it and snug it tight - don't over-tighten it as you could strip the thread in the sump which would require removing the engine to fix! Remove the oil filter, allowing it to drain, and ensuring the rubber seal isn't stuck on the metal mating surface. Once drained wipe a smear of fresh oil on the new oil filter's rubber O-ring, fitting it a quarter-turn past snug. Check on your owner's manual for how much oil is required for your particular engine, and what grade of oil you should use.

Has it just started making the noise, or has it been doing it since new? Try running it on higher octane fuel and see if the noise goes away.