Gasoline, hydrogen sulfide and burnt cardboard: what do the smells in the car tell us?


“I recognize him from a thousand… ”

The most common automobile odor is the smell of gasoline. Let’s not talk about carbureted cars now: there are almost none left, and the reasons for their gasoline stench are a bit distinctive. Therefore, only the injector, only the mainstream.

In principle, there are many sources of gasoline odor, but some of them manifest themselves rarely. Let’s start with the most popular ones, then we’ll get to the exotics.

So, more often than not, gasoline stinks in the car interior because of the gasoline pump, which is usually under the rear couch. The immediate cause is a rubber ring, a gasket through which the gasoline pump is pressed to the gas tank through a hatch in the body under the seat. Over time, this rubber, like any other, will get cold and start leaking gasoline fumes. The way to fix it is simple – to replace the gasket. And the good news is that in this case, the smell is certainly annoying, but is not too great a danger. It’s worse if gasoline leaks in the engine compartment.

The second common cause is a problem with the gas tank neck. Theoretically it is a separate part, though it may be riveted to the tank. But tightly is not always forever. The seam can leak, too. And the clamp of plastic neck all the more so. True, there is one “but”: there will be nothing leaking in the literal sense of the word – the petrol level is much lower. Unless you fill it up at a gas station, but that’s not exact either. But the stinking gasoline vapors pass there for sure. And the saddest part is that it’s hard to reach when inspecting it.

A less common cause also has to do with the gas tank. Sadly, the iron tank also rusts and sometimes has holes in it. And it can also rub against another body iron or a shattered fastener. Usually such damage is easier to find: the tank starts leaking.

By the way, a plastic gas tank can be ruined on an off-road if you wish. It will stink, too, but not for a long time: as a rule, gasoline will flow out quickly, and there will be nothing to stink. So this is just information for thought.

Causes related to the gas tank are the most likely. Just in case, I’ll name two more: a clogged absorber and a faulty gas tank lid. In the first case, absorber (it’s a thing that collects gasoline vapors and returns them to the tank) fails to cope with its work (for example, filter is clogged), in the second case – the cover in an old car, which begins to let gasoline vapors through. The reasons are not the most obvious, but possible.

If the gasoline smell is not from the gas tank, there is reason to be even more upset. Because leaking fuel under the hood is not only unpleasant to the nose, but also dangerous to life. In a carbureted car, gasoline could leak through all the connections and fittings of the gasoline pump and fuel filter, all right next to the engine. The injector has all these things too, but they are hidden further away. And they leak less often. But here there are small parts, which can be the reason of unpleasant smell – fuel injector o-rings. There will be no puddles of gasoline around them, but the smell is quite possible.

Of course, the smell can appear there, where someone tried to do something with wrong hands. But here the search is simple and obvious: look at everything that was repaired before the smell appeared.

One last thing: don’t look for gasoline leaks with a lighter in your hand. Dangerous, you know.

“And the smoke of the fatherland… ”

The easiest to diagnose, but not the most pleasant smell is the smell of exhaust. If you smell it in the cabin of your car, not standing in a traffic jam with KamAZes, there is a reason to strain: this gas is very dangerous to life and health. It is much easier to look for leaks in frosty weather – the smoke, coming out from somewhere under the car in a wrong place, is noticeable at once. And what can fall apart in the exhaust system, we have already told in detail.

Another thing is if the smell of exhaust gases is felt in a traffic jam or in a dense stream in the city. If old trucks stand next to each other and flail with their diesels, it’s from them that the smell of exhaust gases appears in the cabin. It is not necessary to panic, but it is possible to take some measures. Firstly, it is desirable to switch your heating or ventilation system to recirculation mode (the air from the street will not get into the cabin). Secondly, you should think about what can go wrong with cabin filter (if there is one at all). Maybe it makes sense to stop cutting when buying cheap paper of dubious manufacture and pay attention to some normal manufacturer. Sometimes it happens that the filter is just not very well made and does not sit tightly in its place, letting in all the smells from the street.

But it is important to understand that in the majority of cars it is impossible to avoid the smell of exhaust from an old truck or bus completely. Especially if you stand right behind its exhaust pipe. Sad but true. By the way, with this incredible aroma of an old diesel can be confused with another smell – burning oil.

It leaks and smells.

The stench of old diesel is essentially the stench of burning oil. So the smell is similar, but unlike the first situation, the car stinks on its own – without any traffic. So if the road is clean and the smell is there, you need to check your car.

The main reason for the burning oil smell is its leakage from the engine. There can be a lot of sources, but first of all it is worth checking the valve cover. It sometimes “drips” very sneakily: imperceptibly, without obvious oil drops, but due to its upper location it floods the whole engine from head to foot (pardon, to the sump of the crankcase). It’s good if the valve cover gasket (or sealant joint) is immediately visible, but if there’s a cap on the motor, you’ll have to take it off. If it’s dry, you have to keep looking. Glands, joints, gaskets – leaks can be everywhere. So there’s a lot of room for creativity.

Sweet? Bitter!

One more smell is not perceived by everybody as dangerous, and they should be. The smell is specific – sweet. That’s what antifreeze smells like. If you can smell it in the cabin, it means that the antifreeze is leaking somewhere here too. As a rule, it is the heater radiator, which is somewhere under the panel.

At first, of course, you should check antifreeze level in expansion tank – you may overheat the engine. Then, we inspect the floor. If they are wet, we poke them with a finger and see what he got into. Most likely, in antifreeze. The heater seldom bursts badly at once, so apart from the smell, two other things may alert you: the windows sweating too much from inside and sometimes – hardly noticeable fume, flying out of deflectors when you switch on the heater.

Although the smell tastes sweet, the situation can be bitter. For example, the second Kalins and Grants have the ability to burst the radiators of heaters instantly, and their location provides a flow of very hot bubbling antifreeze directly to the driver’s legs. And it threatens not only with burns, but also with emergencies. Even without it, the story is not pleasant: to drive with running antifreeze is dangerous for engine’s health. So, the sweet smell is a reason to urgently look for a coolant leak.

Paper? Cardboard? Sawdust?

This smell is hard to describe in words, you have to smell it. How do you imagine it? Well, let’s say like burning a dirty and oily cardboard box on red-hot bricks. That’s what burning brake pads smell like. The cause is usually impossibly trivial – a jammed caliper. The smell is better felt after stopping and outside the car. Carefully touch the discs of the wheels, and if one of them is hot – the culprit of the smell is found.

The rest is up to your taste. Either go to the service, or do it yourself. But to start repairing the caliper is also quite dangerous. Okay, if you just wear out the pad too quickly. Worse, if the brake disk will overheat (it will be at least warped) or the brake fluid will boil. In this case, you can stay without brakes at all. And also constantly hot wheel will threaten hub bearing grease very quickly. In a word, consequences may be various, but always unpleasant.

Something seems to be burning.

Everyone probably recognizes the smell of burning plastic. It’s the smell that melts the wiring insulation and everything associated with it: burned switches, connectors or contacts. First of all, you should pay attention to what the smell is associated with. It is worse, if it is right after you turn on your ignition (by the way, the contact groups of ignition locks love to melt – there is a lot of current there. For example, on starter). If not, we check lights, heaters, music. Especially, of course, what is installed out of order.

Head light wiring burns most often, if you put too high power bulbs. In some cars (especially American ones) contacts of light switches that don’t have relay switches in their circuit get burnt with an enviable regularity. If the smell of burning appears after turning on the light, you can safely start checking them.

You can also look at the fuse box. Sometimes a Chinese fuse is the only thing left intact after the rest of the car burns out.

A separate story is the smell from the power wiring and units like the starter or alternator. It can burst into flames, and since the source of the smell is not localized in the passenger compartment, but under the hood, it is not always found in time. Moreover, the cause may not necessarily be closed windings of the generator, but, for example, in a bad contact of the plus wire or “common ground”. Fortunately, this happens rarely.

Probably there is no need to say that this smell should not only cause panic, but concern should cause frantic. It is impossible to drive with it, go to service at once.

Who has done it?

There are two more unpleasant smells in a car, which are sometimes confused. The first one is very specific. They say about it delicately: hydrogen sulphide smell. Spare me the description of this odor, I’m squeamish. The appearance of such a smell at high speed is usually not the fault of an overly frightened passenger, but of the catalytic converter. Theoretically, it’s not dangerous: the catalytic converter gets very hot under heavy load. But sometimes it can be a signal of some malfunction. For instance, in ignition system, if petrol burns down somewhere in exhaust, raising temperature of exhaust too much.

If the smell bothers you too often or palpably, it makes sense to go for a diagnostic. And if the mileage is too high and you suspect the catalytic converter is clogged, you can have it removed (or replaced, if your dad is a Rockefeller).

The second smell is similar to the first, but not as unambiguous. It is the smell of rot or mold. The smell is safe in principle, but unpleasant. And it can have many sources. If you do not keep the cabin clean, an apple under the seat may exude the aroma of rotting from last year. God forbid to spill some kefir or yoghurt on the upholstery – it is possible to remove them infinitely long time, but they aromatize your car ruthlessly. However, it’s boring.

It’s more interesting if the odor appears after the air conditioner is turned on. It means that it should be cleaned. If you do not care about this procedure, you can get some disease: whole colonies of microbes and bacteria live and flourish in the system.

And the last thing: the smell of rot can be caused by high humidity of a salon. We are not going to look into extreme cases (holes in the VAZ-2106 floor), but let us remind you, for example, about drain holes – they must be cleaned. A sunroof, doors (especially back doors of crossovers and hatchbacks), a trunk lid on seals may leak. It is necessary to struggle with moisture, otherwise the car will rot offensively fast.

And one more time: there must not be any smell of “technique” in a salon. You should not calm yourself with the fact that there is oil, and gasoline, and hot iron. Certainly, there are, but it is impossible to smell them inside. And if it smells, something is wrong. And it’s very likely that it’s going down a dangerous path.


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