Mazda Hatchback Range

The first thing to do is drive the car yourself and see if there’s a pattern to what’s happening. Until then, you have even less idea of what’s going on and a diagnosis is all but impossible at that point. You might find that the car is cutting out after a period of driving (maybe caused by a dirty fuel filter) or when the engine reaches a certain temperature (possibly a sick crank angle sensor).

I’d also recommend an electronic scan to see if any fault codes show up. These codes can be very specific and will often lead you straight to the root of the problem.

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.