Warning noises from under the hood of a car that cannot be ignored

Every car owner knows how his car sounds in good condition. The appearance of extraneous noise, clatter and cod should be alarming. It is better to play it safe and show the car to specialists in order to detect and eliminate defects in time, as well as to avoid larger breakdowns and expensive repairs.

The appearance of extraneous noise from under the hood may be due to the wear of the power unit or other components of the vehicle. The most alarming symptom is ICE tapping, which can appear at idle or high speeds, in cold weather or when the engine is warm, be present or disappear, and also sound muffled or loud.

Whistle and hum

The whistle of attachment belts is usually associated with their tension and most often manifests itself in an unheated car or when you sharply press the gas pedal. If belts with roller tensioners are installed, then the problem is solved by replacing these parts. How can a whistling bridle be dangerous? If the belt rotates the power steering pump, generator, air conditioning compressor, then if the belt breaks, the car will be left without power steering, battery and heating / cooling system, respectively. In this case, it will be possible to get to the service or to the house, charging a good battery is enough for about 50 km. If the cooling pump is driven by the belt, then you should not drive a faulty car. Eliminating the consequences of an internal combustion engine overheating is expensive.

One of the reasons for the squeak, crunch and hum is the wear of the generator bearings. In this case, they will need to be replaced, since the load on the belt increases, and its tension becomes insufficient.

Do not delay repairs. If the whistle is heard regularly, then the belt has begun to wear. And in some car models, attachment and timing belts are located close to each other, and a break in one of them can most likely lead to a break in the second.

Something is knocking

Knocking from under the hood can be of different intensity. If two timing parts made of hard material are worn out, the motor can make a uniform knock for a long time. If the soft elements that work in tandem with the camshaft, main or connecting rod bearings are worn out, then the knocking sound will increase rapidly. Here are a few possible causes of failure:

Pistons can make a dull click if even a small gap has appeared. Usually, the defect manifests itself at low speeds or in cold weather, and when the car warms up, the thermal expansion of the piston occurs and the clicking disappears.

Piston pins knock loudly, the knock is clearly metallic. It is located in the cylinder block. It shows up well when you press the gas pedal hard or press the accelerator to accelerate. May occur due to the use of unsuitable fuel or under heavy loads. For example, when going uphill in high gear.

Main bearings (liners) of the crankshaft. Metallic tapping, well audible at low speeds of a warm engine. With a sharp gas supply or gas discharge, it is heard from the crankcase area. Knocking can be caused by low quality engine oil. In this case, flushing the system and changing the oil is required.

Connecting rod inserts. The tapping sound will be similar to a main bearing failure, but louder. Increasing intensity at the moments of a change in speed indicates the need for urgent repairs, otherwise the engine may “catch a wedge”.

Something is cracking

If the machine crackles noisily during operation, then it may be a faulty phase regulator. This is a problematic place for various Toyota car models, as well as for Renault with a 1.6-liter engine with 113 horsepower. In addition to cod, symptoms of a malfunction can be unstable rpm during warm-up and lack of traction in a certain range.

How to fix the problem? It depends on the particular ICE. If the cause is in the phase shifter valve, then you can try replacing the oil with a better one recommended by the car manufacturer. Replacing the camshaft position sensor (sometimes called the phase sensor) can help. But before buying this rather expensive part, do a diagnostic in a good car service.

A stretched chain can also cause rattling, growling or humming. Usually, before the appearance of this malfunction, cars travel up to 200 thousand kilometers, but there are exceptions when you can hear the “death song” of the chain at any time. A breakdown should be reported by the Check engine light on. If the mileage is low, then the problem is most likely in the tensioner, which needs to be changed.

The most dangerous causes of knocking

If the starter buzzes with a transition to a rattle. This is an SOS signal. Means that the starter does not disengage from the engine after starting. Anchor breaks in seconds. Starter is a replacement.

A slight whistle from the turbo is normal. A strong whistle or hiss is a sign of air leakage in the cold part and gases in the hot part. If the turbocharger makes a grinding sound, then the impellers are touching the turbine and compressor volutes. And this is the verdict of the engine.

Variable intake system. If the engine intake piping has a mechanism for changing the length of the channels, dampers inside it can make a knock. Loose shutters can come off the axis, and this is dangerous.


Any breakdown of the internal combustion engine is dangerous. If the mechanism jams, the repair will cost several times more. In the worst cases, the engine is changed as an assembly, spending up to 50-70% of the cost of the car.

When you hear that the engine is knocking, you need to immediately find the place where the noises come from. If they are emitted by the upper part of the engine, then you can get to the service station on your own. But you can’t delay the repair – the longer you wait, the higher the cost of work. The most dangerous knocks come from the bottom of the engine. When you hear them, turn off the car immediately. You will have to get to the place of repair in tow or on a tow truck.

Some problems can be solved with little bloodshed. For example, when adding oil to the recommended level, the knocks of the crankshaft and hydraulic lifters disappear. But driving on a “dry” engine could damage some components. It is better to take the time and visit the service station for diagnosis. In most cases, the wizard will reveal hidden problems. Repair at this stage will require less time and money.

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