Have any of these ever happened to you? Don't worry, Haynes is here to help...
1) The Car Has Gone Into Limp Mode!
If you’re driving along and your car suddenly refuses to go past a certain rev limit, or if it will only go 30 mph, there’s no need to panic. This is a trait of modern computer controlled cars, but don’t worry. The car is doing this as a safety measure.
Modern car electronics are wired into pretty much everything, so if there is an issue somewhere along the line, the car will know. When the computer detects a major fault, besides lighting the check engine light (CEL), it will go into what most manufacturers call ‘limp mode’ which limits the power, revs, and speed of the car. The idea behind it is to stop any serious damage occurring.
'Limp mode' means you won’t be stranded on the side of the road, but you won't be moving very fast. You should be able to get home or to a garage safely, though slowly. Sometimes, just like your computer, shutting the car off, waiting a minute and then restarting it, will allow you full power again
2) The Serpentine Belt Snapped!
People often get the serpentine auxiliary drive belt and the timing belts mixed up. The timing belt is of course a crucial part of your engine and if it does snap, it could mean you need a new engine. Which is why periodic timing belt inspections and replacements are so important.
But as the name suggests, the serpentine auxiliary drive belt is not quite as important. This belt drives things like your car's water pump, alternator, air conditioning compressor, and sometimes the cooling fan.
If it snaps, you can still drive the car, though not for very long. A snapped serpentine belt means the battery won’t be charging, but a full battery should still have enough juice to get you to safety. The more pressing issue is likely that coolant is no longer being circulated through the motor by the water pump.
Avoid using any electrical items like wipers, radio, or rear window defogger, and turn the heated control to hot, but avoid turning on the blower. You should be able to drive a few miles in open traffic without issue, or get to a safe parking spot in traffic before the car overheats.
Don't miss our one-job manuals for fixing the most common problems on your specific vehicle!
3) Where Is All This Steam Suddenly Coming From?
Admittedly an overheating car is rare these days, what with all the computers adjusting the ignition and fuel mixture, and even the cooling fan speed in some cars (see number 1 about ‘limp mode’). But it can still happen because of a leak, or a bad serpentine belt (see 2 above).
If you’re lucky enough to own a car that has a temperature gauge (a surprising number of new cars don’t) it’s simple enough to keep an eye on it. If the temperature does suddenly skyrocket, the course of action is simple: turn off the motor ASAP. If the gauge just starts to creep up above the normal operating range, especially in heavy traffic, hot weather, or going up a big hill (or a combination of these factors), there is no need to panic. Turn the AC off, turn the heater on, try to get to more open road, or if climbing a hill, downshift to get the revs up.
There’s no quick fix here. If you do boil over, you have to stop and let it cool down. Once it is cool to the touch, you can check the overflow tank or radiator and see where the coolant level is.
NEVER OPEN THE RADIATOR CAP OF A HOT MOTOR!
If the coolant is low, you can add some water, which may well fix the issue for now.
Most importantly, though, stopping the car and letting it cool should stop any further damage, like a blown head gasket. Modern aluminum engines don’t like prolonged exposure to high temperatures.
If you don’t have a temperature gauge, your car will flash a warning light on the dash should things begin to get too hot, before steam shoots out. Again, stop the car and let it cool down.
And whatever you do, DO NOT mess with things while it’s still scorching hot.
Unfortunately, if just topping off the radiator and letting the engine cool doesn't solve the issue, you are most likely going to have to call a tow truck, or drive to the nearest service station.
4) Wait, Where Are My Keys?
We’ve all been there. That sinking feeling when you shut your car door then suddenly see your keys on the seat, or even worse in the ignition. But what do you do? Smash the window?
Sure, that's an option, though a bit too extreme. Bend the top of the door back? Unless you drive something exceptionally poorly made, or you’re the Hulk, this isn’t going to work either. You’re going to have to call a locksmith, unless you happen to be good with a coat hanger, and also have one handy. If you have a late model car, especially a GM, you may have the option of calling the company's customer service roadside assistance hotline. Many cars these days can be opened remotely via satellite or cellular phone network, if they are equipped with keyless entry and an internet connected infotainment system.
You can prepare for this sort of situation by being a AAA member, or having another roadside assistance service. They can often open the door with little effort, and no additional cost.
If you have completely lost your keys however, the only option is a good locksmith. You can make his job easier, and your bill smaller by writing down the key code and keeping it in your wallet. It is also useful to read your owner's manual and see what it says about getting replacement keys and alarm fobs for your particular make and model, before you have to find out the hard way late one rainy night.
It’s usually far cheaper to get a new key from the dealer or made from the code than having a locksmith mess with the lock to make a key that fits. Trust us, we’ve been there.
5) This Doesn't Smell Like Diesel!
If you drive a diesel powered car or truck, it’s surprisingly easy to accidentally fill it up with unleaded gasoline. You can’t do it the other way around, as all modern gasoline cars have a smaller filler neck than diesel, so the diesel pump won’t go in. If on some bleary-eyed Monday morning commute you fill your TDI with unleaded do not under any circumstances start the car.
If you need to move it, push it. DO NOT START THE ENGINE
As long as you don't start the engine, fixing this is just a matter of draining the tank (though you’ll probably have to pay a shop a few hours labor to do it). Once you do, it’s just a case of filling up with the correct diesel fuel.
If you try to start it though, you’ll pump all that gasoline into an engine that doesn’t know what to do with it. Not only is gasoline bad for all the rubber and plastic parts in the diesel's fuel system, it will cause detonation and all sorts of bad things for the few moments the motor likely runs.
