Ask The Guide

The important thing here is that you do actually check you oil regularly. It’s a basic home maintenance chore, but one that too many car owners ignore.

That said, it doesn’t really matter whether you check the oil hot or cold, as long as you do it the same way each time. That’s because cold oil will contract a little, while hot oil will, thanks to thermal expansion, appear as though the level is a little higher. All engines use a little oil, so what you’re checking for is any change in the engine’s drinking habits that could indicate engine wear starting to show up. That’s why it’s best to check it the same way every time.

You’re also right in suggesting that the oil takes a little while to make its way back into the engine’s sump when the engine stops. Checking it straight after a drive means it won’t have all returned to the sump and you’ll get a low reading on the dipstick. So, leaving it for a few minutes is the way to do it. Also, you shouldn’t trust a dipstick reading when the engine has been run but not reached full operating temperature. Cold, thick oil won’t drain back into the sump completely and, again, you might have a low reading on the stick.

If the noise is a metallic rattling noise, then you might be on the right track here. But as well as the timing chain, it could also be the tensioner that keeps that timing chain tight at fault. The fact that the noise goes away after a few seconds suggests that the tensioner, rather than the chain, is at fault. But they could both be worn.

What’s happening is that the tensioner is hydraulically operated and needs engine oil pressure to do its job. When the engine has been sitting overnight, there’s a slight time delay between it starting and enough oil pressure reaching the tensioner to tighten the timing chain and stop the noise. What you’re hearing is the chain flailing around until the tensioner steps up and takes the slack out of it, at which point it stops rattling and goes silent.

Why doesn’t it happen every time you start the engine? Because the tensioner needs time for the oil to drain completely out of it. If the engine has only been stopped a short time, there’s sill enough oil in the tensioner for it to build up pressure quickly and keep things quiet.

It doesn’t take much of a leak to allow enough rainwater into a car to wet the carpets. Given your car is a 2018 model, I’d be surprised if the rubber seals have deteriorated to any great extent. The best bet is to open the doors and hatch and have a close look at the surface of the seals. If there’s a nick or a cut in the rubber, you’ve probably found the problem. But also look for a twig or other piece of rubbish that could be stuck to the rubber and be forming a gap for the water to enter.

If the front floors were wet, the advice would also be to check the drain hose for the air-conditioner, but if it’s the rear floors, it’s almost certainly rainwater. Don’t forget the obvious stuff like a window that looks closed but is actually open a fraction.

Without a doubt, the best thing to do now is the have the car electronically scanned. That’s because there are literally hundreds of things that could cause this sort of problem, ranging from (but hardly limited to) a sick fuel pump, a blocked fuel filter, worn injectors, a fuel leak, poor ignition, a low-voltage battery, dirty air-filter, blocked or damaged exhaust, a stray electrical problem and much, much more. Even something simple like a fuel rail that is not holding pressure when the engine is switched off, can lead to symptoms very much like yours.

Hopefully, the on-board computer has logged these random starting problems and will be able to tell a mechanic what’s wrong. Otherwise you’ll simply continue replacing parts that weren’t the problem in the first place. And that costs time and lots of money.

Any time a mechanic sees an illogical pattern of faults like these all at once, their suspicions are always drawn to the body computer. This computer controls all the functions you’ve mentioned as well as hundred more, and when it goes on the fritz (as computers are wont to do) you can suddenly get all sorts of weird behaviour, just like you’re reporting.

Take the car to an auto electrician who might be able to make sense of what could be a complex wiring issue. But the smart money says body computer every time. These can be replaced by a new computer, second-hand ones from a wreck and sometimes even fixed by very clever people. If the auto electrician can’t offer any advice, get online and see what help is out there.

The temptation is to assume that the car is simply low on AdBlue (an additive that is sprayed into the exhaust of diesel engines to clean up their tailpipe emissions and make them less toxic). When this is depleted, the engine is programmed to warn the driver that the level is low, and then not to restart until the AdBlue has been topped up. This is possibly what the dealership did to remove the warning.

But there’s a chance that the AdBlue injecting system has a fault somewhere and the problem is not as simple as low AdBlue fluid. That’s why the error message has returned. Or, you may simply have a dud sensor that continues to think the AdBlue tank is empty.

If you mean shuddering and vibration when you take off from rest, then you’re possibly experiencing the same problem that many owners of this model Nissan have already reported. The problem is caused by wear in the CVT transmission which is allowing the steel drive belt to slip. As the belt slips and grips and then slips again, the driver experiences less-than-smooth acceleration.

The safety recalls (which were actually technical service bulletins) you’re referring to all occurred within the North American market and haven’t been extended to Australian X-Trails (that I know of). Unfortunately, US consumer law is quite different from ours and consumers have very different rights and obligations.

It would be worth having the car assessed and then approaching Nissan Australia’s customer service department to see if there’s any help on offer. But given the age of the vehicle, I wouldn’t be holding my breath. That said, I totally understand your point of view, and 11 years is probably not a suitable lifespan for a modern automatic transmission, given we’ve been making cars for more than 130 years, and Nissan (in one form or another) for the last 90 of those.

You may have a collection of problems rather than just a single one. The vibration through the steering wheel could simply be the vibrations from the diesel engine travelling up the steering column and into your hands. Does the vibration go away when you rev the engine to just off idle? If so, perhaps an adjustment to the idle speed is all that is required there to move the engine out of its resonant patch.

A vibration in the cabin could be a worn wheel bearing, out-of-balance driveline, a worn torque converter, broken or worn engine mount, broken exhaust mount, damaged tyre, a wheel out of balance and plenty more. But the play in the front driveshaft coupling would be a smart place to start looking. Again, the problem comes and goes because of the harmonic periods inherent in things that spin very quickly. Any out of balance problems can easily show up as transient vibrations inside the car.

There’s every chance this is caused by a small amount of wear and slack in one of the joints in the driveline. If that’s the case, those joints and couplings need to be checked and the worn one(s) replaced, as continuing to drive as it is could see the driveline fail spectacularly at speed.

The reason you feel the jolt on the flat and not when you’re parked on a hill is that the driveline is relaxed on the flat, leaving a little slack for the thump to occur. When parked downhill, gravity has caused the driveline to take up that slack (plus your foot is probably on the brake, preventing the car rocking or moving at all) so the thump can’t occur and, therefore, isn’t felt.

Whether this is a problem or not all depends on how much oil you consider to be too much. There’s an old school of thought that says an internal combustion engine shouldn’t use any engine oil. That’s not actually accurate. A small amount of oil is scraped past the engine’s piston rings and burned every time the engine turns over (which it typically does at anything up to 7000 times a minute). So some reduction in the level of oil in the sump is pretty much inevitable.

Some modern engines also use low friction internal components to make them more fuel efficient and, in some makes and models, this has had the effect of increasing oil consumption. Again, this is perfectly normal and the pay-off is you use less fuel.

Rather than just a drop in oil level, you should be looking at the drop compared with the kilometres you’ve covered. A car that consumes, say, a litre of oil (or even two litres) between its 10,000km oil changes is not a problem at all. Some manufacturers even say a greater level of oil consumption than this is still within acceptable tolerances. Anything up to 1.5 litres per 1000km can still be within a car-maker’s specification.

What you’re really looking for when checking your oil level is any change in the engine’s oil sipping habits. A sudden increase in the amount it normally consumes is when you need to start looking more closely.

That said, if the car is using too much oil, then it’s either being burned in the engine (suggesting worn engine parts) or it’s escaping the engine somehow (otherwise known as a good old-fashioned oil leak). A big patch of oil on the ground where the car is normally parked means you need to go hunting for a leak.