Ask The Guide

I’d be interested to know what happens after the 30 minutes when the system switches itself back on. Does it disable again if you give the connecting plug a wiggle? If so, it’s probably a poor electrical connection somewhere inside the plug assembly. If you need to turn the ignition off and back on to make the system disable itself again, then you might be dealing with some kind of computer (body computer?) problem.

The thing is, if this is a genuine Isuzu accessory option, then it should come under the car’s new-car warranty. At which point it’s Isuzu’s problem to fix, regardless of whether the dealership you use has seen this issue before or not.

The filling point for this transmission is on top of the gearbox, under the ECU (drive-line computer). So, to access it, you’ll need to move the computer (which attaches to the battery tray) out of the way. Take lots of photos before removing bits and pieces so you’ll know how it all goes back together.

However, it’s doubtful that a lack of gearbox oil is your problem here. If the oil was low, the transmission would probably be making some seriously bad noises or would be completely seized up, not just refusing to shift out of reverse. The refusal to abandon reverse probably has more to do with a mechanical selector problem. But don’t rule out a worn or maladjusted clutch, either.

It sounds very much like there’s a blow-by problem with this engine. The pressure created by the combustion process is somehow getting past the pistons and into the crankcase, causing the dipstick to leave its tube and blowing oil all around the engine bay.

Blow-by is often caused by worn or broken piston rings or a damaged piston itself. But modern turbo-diesels are also prone to problems with their crankcase ventilation and emissions-control systems which can become full of gunk and not allow the crankcase to breathe properly. At which point, the same symptoms can occur.

A mechanic will be able to do some tests and determine what’s causing the pressure build-up inside the crankcase. If it’s internal wear, a rebuild may be required. But if it’s a build-up of crud inside the emissions-control systems, a manual disassembly and clean might be required. Either way, your car’s warranty might cover you for this, so the Hyundai dealer is your first port of call.

The 4X4 indicator light should appear on the dashboard only when you’ve selected four-wheel-drive. So, no, it’s not normal for it to flash on an off randomly. Since it’s unlikely the car is engaging four-wheel-drive itself (you’d feel it anyway) the fault is probably either a short-circuit in the globe’s wiring or a faulty sender unit that should switch on the light when 4X4 is selected.

The coincidental nature of these faults would make most mechanics suspect the body computer is having a nervous breakdown. This computer is the one that controls functions ranging from central locking, the immobiliser, power windows, dashboard and even the entertainment system. It’s also responsible for the indicators, climate control and probably the gear selector. See the pattern?

And because the computer itself – rather than an individual component – has gone on the blink, it won’t always throw an error code. An auto electrician is the first place to visit as your diagnosis of an electrical fault is almost certainly spot on. Don’t rule out a simple bad earth connection, either, as these can also cause electronic havoc.

I’m not aware of a recall or class action over this problem, but it would definitely be worth talking to Mercedes-Benz’s Australian customer service department to see if there’s any help on offer. Provided the car has a complete service history, you might get a sympathetic ear, but, that said, don’t count on it.

The counter-argument you’ll likely be met with is that you should have been paying attention to the car’s temperature gauge and stopped the engine when it began to overheat. "That’s why cars have temperature gauges", will probably be the response at dealership level, but go straight over the dealer’s head and talk to head office.

A manifold leak will throw the engine’s fuel-air ratio out the window and can cause poor cold running and hard starting. The old school way of checking for a vacuum leak is to get the engine idling and then spray either carburettor cleaner (or something else flammable) around the intake area of the engine. If the engine suddenly picks up revs, you almost certainly have a vacuum leak. But be careful, spraying flammable stuff around a running engine comes with a fire risk.

The other thing to check would be the throttle body and the sensor attached to it that tells the computer how much throttle has been applied. Again, these can start to give false readings, throwing the fuel-air mixture out.

That’s a fair question, because the subject of towing limits is a pretty topical one right now as caravans get heavier and heavier and the police crack down harder on overloaded vehicles. That said, Audi makes no distinction between the towing capacity of its Q7 based on what accessories (including the moon-roof) are fitted.

But it definitely pays to remember that many vehicles, once hitched up to their heaviest legal towed load, can then be very close to their Gross Combination Mass (GCM) which is the mass of the trailer, the vehicle and everything in it including people, fuel, luggage and any aftermarket accessories fitted to it.

As an example, there’s one US-made ute on the market now that, when towing its maximum legal load, is so close to its GCM (has so little payload remaining) that it could only be legally operated by one small person with no luggage, nothing in the tray and no fuel in the tank.

The three brake lights are almost certain to be on the same circuit, meaning that if two are working, the third one is likely to be suffering from something as simple as a blown globe. Perhaps the globe is loose in its socket, but if two out of three are working, then you probably don’t have an issue with the wiring or fuses.

The wiper issue could be to do with the body computer (which controls a huge number of a modern car’s functions) but, equally, could be something as simple as dirty contacts in the switch part of the stalk that controls the wipers. Some contact-cleaning spray into the switch might do the trick.

Based purely on your symptoms, a broken clutch is the most likely cause. When a clutch loses the ability to fully disengage the engine from the transmission (through either wear or damage) the gears can become very difficult to select. Sometimes they will engage with a crunch, at other times you may not be able to select them at all.

This is a different problem to a worn clutch which has lost its clamping ability and is slipping, but the ultimate fix is the same: A new clutch assembly.