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This is a really common type of question here at CarsGuide. It seems a lot of car-makers are using these speed warning systems and, in many cases, they’re more of an annoyance than a help.

In your Kia, speed sign recognition which is part of the adaptive cruise-control feature is the culprit. When the car’s cameras spot a speed sign, they compare that info with how fast the car is actually going (sometimes using co-ordinate information from the sat-nav as well). Sometimes, however, the sign detected relates to a side-street or roadworks on a side street, giving you a false alarm. Either way, not everybody likes this warning system.

There’s good news and bad news in the case of your car, Steve. The good news is that you can go into the menu system, select Driver Assistance, then Vehicle Settings, then Speed Alert, and you should find an Off setting that should disable the warning. The bad news is, you have to do this every time you start the car, because the default setting is On.

Perhaps the dealer can suggest a way of turning it off permanently since it appears as though a software update at your first service has enabled the system since you bought the car.

You’ve probably hit the nail on the head, and it is a seat-belt warning you’re hearing. Even though you may have the belt properly fastened, if the sensor that is supposed to detect the seat-belt being latched is not working, then the car will think you’re driving around unrestrained.

Jaguars of this era were not universally known for the quality of their electronics, so it’s very possible that this is precisely the problem. The catch then is that you need to check each seat-belt for a dud sensor, and there are five of them in the S Type. Other things that could trigger the same sort of alarm could be that the park-brake is not fully released or that there’s a door or bootlid ajar. Check it all and rule things out one by one.

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.

This model X-Trail is fitted with active lane-keeping assistance which is sort of a helping hand when the driver isn’t keeping the car in the centre of its lane. It could be that this system is what’s causing the car to feel like it wants to pull you into the next lane.

You need to have this checked under warranty as soon as possible, since it’s an obvious safety issue. This isn’t just a Nissan thing, either. Many brands have had complaints about these systems, and in some cases, cars fitted with collision-avoidance systems have been known to slam on the brakes when the car’s camera 'sees' something like a wheelie-bin on the footpath and mistakes it for a truck entering the road. Speaking of which, your lane-keeping assistance is controlled by a camera at the front of the car. Have a quick check to make sure there’s not a huge dead bug confusing the camera.

The workshop you want is a specialist air-conditioning business. Air-con might have a simple job to do, but it’s a complex system with lots of interlocks to protect the various bit and pieces. If, for instance, the gas level is low, a sensor will detect this and disable the air-con compressor so the system can’t be damaged by running with low gas or lubricant. So, simply replacing sensors and other bits and pieces randomly is a great way to tear up money and still not fix the problem.

You need to have the system checked by somebody who understands the technology. They will test for leaks, check whether the system is holding pressure and then check the operation of the rest of the hardware including the compressor, receiver-drier, condenser, blower-fan and relevant filters.

If you’re lucky, the system may just need re-gassing, but you could also be up for some expensive new parts if there’s other damage or problems. But without a proper diagnosis, you’re flying blind.

Sandy conditions are incredibly hard on every aspect of a four-wheel-drive. The sand itself constantly shifts under the tyres and clings to them as well, dragging them down and making the engine and transmission work very hard to maintain progress. You may have already noticed that you use a lot more fuel in sandy country and it’s all because you need to be constantly making more power to maintain speed than in normal conditions. Turbocharged engines and automatic transmissions, in particular, can get very hot very quickly in sand.

With that in mind, it’s very possible that something in the driveline got hot enough for the car’s computer to go into limp home mode to protect what ever was hot from damage. Limp home mode often involves limiting engine revs and turbo boost, both of which contribute to heat production. This would explain why the car would not climb a crest but came good after a break.

Transmission fluid should generally be a pretty pink or red colour. If it’s black (and/or smells like burned toast) that suggests that it is way overdue for a change of fluid and a new filter, and also that there could be lots of wear inside the transmission.

Tiny bits of the clutches and bands that control an automatic like yours wear off over time and it’s these that are discolouring the fluid. That fact that they’re black, also suggest they’re burned having been overheated at some point in the past.

A transmission shop should be your first port of call, with instructions to diagnose what’s wrong and work out a strategy from there. If the transmission is badly worn, it may need replacing or rebuilding. But you might be lucky and discover that the fluid is simply old and depleted (from a leak somewhere) and the transmission may recover with a full service. Don’t count on it, however.

It all depends on what you call the serpentine belt. If you mean the toothed rubber belt that drives the camshafts, then yes, the engine will need to have its valve timing re-set before it will run again with a new belt. If this is what has happened, you’re lucky that the 3S-FE engine in your car is what’s called a non-interference engine. That is, if the belt brakes, the pistons will not crash into the valves, destroying the engine. In an interference design, you’d be looking at a whole new engine.

If, however, the belt you refer to is the one that drives the power-steering pump, water pump and alternator, then you should be able to simply replace the belt and be back in business.

You could be dealing with either a worn transmission itself (where wear inside the gearsets, shafts or torque converter has made something sloppy) or there’s something else in the driveline (such as a differential or universal joint) that has likewise allowed some looseness or play to enter the equation. In either of those cases, a thump or clunk during shifts can be a symptom. It feels worse under acceleration, as that’s when the maximum stress is on all those moving, meshing parts.

Sometimes, a transmission can be serviced and adjusted to get rid of thumping or banging during shifts. Take the car to a transmission specialist who will be familiar with this transmission and may be able to return it to civility.

Air-conditioning can really add another layer of stress to an engine. Since the air-con compressor is driven off the engine (via a belt) it's just another thing for the engine to deal with. And since the engine has to make more power to run the air-con and travel at the same speed, it uses more fuel. And more fuel burned equals more heat, it's pretty basic physics to that point.

Any vehicle with a cooling system that is already a bit marginal can easily be made to overheat by switching on the air-conditioning. So the first thing to do is make sure there are no leaks in the cooling system, the radiator is not clogged internally or covered externally in dead bugs, the radiator hoses are not collapsing when you rev the engine, the water pump is working efficiently and the radiator cap is holding pressure (the boiling point of the coolant rises as you pressurise the system. Again, basic physics: Water boils at 100 degrees-C at sea level, but at the summit of Mount Everest, if you set up your camping stove, you'd boil water at just 68 degrees-C due to the lower atmospheric pressure).

The other thing to check is the condition of the cooling fans. The engine will have its own fan, but cars with air-conditioning usually have a second cooling fan that starts up when the air-con is switched on. You can tell if this second fan starts up by listening for it when you hit the A/C switch. If it isn't coming on (or the engine's fan is broken, slipping or doesn't have the correct shroud fitted) than this can easily lead to overheating.