Ask The Guide

Traditionally, Mercedes-Benz has taken the entirely logical step of printing a legend of the fuses and what circuits they relate to on the inside of the fuse box cover. By referencing this, you can quickly identify what each fuse does while you’re in there checking whether they’re blown or not.

For some reason, however, sometimes Mercedes placed a paper diagram of the fuse layout in the boot with the jack and tools. So check there as well. The owner’s manual should also offer this information in the electrical section. If none of that works, you can Google the make and model and ask for fuse box information.

Don’t forget, either, that there are often two fuse boxes in many modern cars; one under the bonnet and one under the dashboard or inside the glovebox.

Actually, this is simply how a CVT operates. When you load the engine (and towing a caravan is a great way to do that) the transmission will switch to a lower ratio in order to keep the engine in its comfort zone and making enough power to keep everything moving at the speed at which you’ve set the cruise control. Because there are no set ratios in a CVT, this can sound a feel very alien when it happens. It's one of the things many people dislike about CVTs.

When you turn off the cruise control and allow the throttle to return to idle, the car detects that the crisis is over and changes the ratio to allow the engine to slow down as less power is needed. And that’s why it all feels like it’s returning to normal. But, really, what you’re hearing and feeling is just the CVT doing its thing.

First things first: If you can smell coolant when the engine is warmed up (or any other time) then you have a leak somewhere. Coolant leaks can be hard to spot as they are not always large and are often located in weird, hard to see places. But if you can smell it, it’s escaping the cooling system somewhere and you need to locate it and fix it.

If you have a slow leak, it’s possible you could drive for weeks without the car overheating, but eventually the engine will start to notice the low coolant level and run hotter as a result. Get it fixed now before you damage the engine. You should be fine to use a bit of tap-water (which will dilute the coolant in the rest of the system) until the leak is found, but don’t leave tap-water (or an incorrect or diluted mixture of water and coolant) in the radiator for the long term.

As for the brakes, the problem does, indeed, sound like warped rotors. Sometimes these can be machined back to true, but often they need to be replaced. Either way, replacing the brake pads at the same time is best practice. Worn pads on new rotors can make those nice, new rotors wear faster than they should.

Jaguar began the switch from the EcoBoost engine to the Ingenium unit in its cars late in 2015. In the XE model, however, that change didn’t occur until late 2017, so a car with a build date after that should have the newer unit. The problem is that a car sold in 2018 (by the time it arrived in Australia) could easily have been built sometime in 2017 and, therefore, could carry either engine. For the definitive answer on what engine a particular car has, the best idea is to check the car’s VIN with Jaguar Australia or a Jaguar dealership.

The VW 1.4 TSI engine uses a cam-chain rather than a rubber toothed belt which needs periodic replacement. As such, the cam-chain should last the life of the engine (and the rest of the car) but experience with this engine suggests that is not always the case and some early versions of this engine have required cam-chain replacement. The incidence of this seems a bit random, with no real pattern emerging with some cars going on to record normal mileages with no cam-chain problems.

The car you’re looking at, however, is a later version, so should be less prone to this. But even so, make sure the car has a perfect service record as poor maintenance can shorten the life of the cam-chain.

You really can’t afford to take any chances with a car’s steering system. The thought of this crucial system failing even at low speeds doesn’t bear thinking about, so if there’s any play or looseness in the system, it needs to be diagnosed and fixed properly with new parts if necessary.

Meantime, Loctite and other thread-locking products are designed to stop fasteners coming loose. These products are not designed to take up slack in worn parts and shouldn’t be used that way. Even if the thread-locker stops the fastening nut coming loose, it won’t do anything about the slack in the joint you’ve already noted.

It sounds very much like your car has a problem with what’s called its clockspring. This is an electrical contact that allows the functions controlled by, or mounted on, the steering wheel to operate while still allowing the wheel to be turned. Over time, the clockspring wears and finally breaks which is almost certainly why you lost the cruise control and horn functions at the same time. It’s also why the airbag light has illuminated, as the broken connector won’t allow the computer to talk to the airbag in the steering wheel.

Most workshops will be able to replace the clockspring, but unless you’re a competent mechanic, leave it to the experts as anything to do with an airbag requires utmost care and respect. Even the experts will disconnect the car’s battery before tackling any airbag issue.

This sounds like a rear differential problem. The differential is designed to allow the inside and outside wheel of that axle to rotate at different speeds (which they need to do as the inside wheel describes a smaller arc than the outside wheel in a corner). If something goes wrong inside the differential, that function can be lost and the wheels try to turn at the same speed in corners. When that happens, the rear end will skip and jump about as the two rear wheels effectively fight each other.

Limited-slip differentials (LSD) often have this problem when the clutches that control the amount of lock-up in the differential fail or become worn. At that point, similar jumping and clunking noises can be felt and heard. In some cases, a limited-slip differential can be restored to health with a change of fluid and perhaps an additive, but in other cases, the unit must be rebuilt.

The rear differential in your D-Max should be the limited-slip type, but around this time, Isuzu made the LSD an option, so it would be worth checking. If it’s an LSD, a fluid change would be the first step towards sorting this problem.

This shouldn’t be a difficult job and it’s a good task to ease yourself into maintaining your own vehicle. The simplest way to do this is to replace the entire blade and spine assembly. This will cost more than replacing just the rubber blade, but is very easy with just one catch to unclip (where the blade pivots on the wiper arm) before the whole assembly can be removed and replaced. You can google tutorial videos on this take which take you through the whole process. It should take only a couple of minutes.

If you’re really stumped by this, some parts stores offer a free fitting service for things like wiper blades. You may have to buy a new pair of blades to access this service, however. But if you watch the process and take note of how it works, you’ll be able to change your own blades in the future.

Conventional wisdom suggests that a fusible link failure is most likely to be caused by either an overloading of the circuit in question, or a short-circuit in that same circuit. The starter motor of a car (especially a modern diesel) consumes a lot of power to make it turn the engine over and that means a lot of load being placed on the electrical circuit. The fusible link is there to act as a fuse and sacrifice itself to prevent damage to the rest of the starter-motor system.

Sometimes, the fusible link can blow by chance or if there’s a momentary spike in the power entering the circuit. If the link continues to blow after being replaced, then you need to start searching for a short-circuit or another problem with the wiring.