Various deviations from the norm may occur as a result of wear of individual elements of attachments, drives, bearings, pulleys or belts. Also, one should not exclude the possibility of a breakdown of the power unit itself and its components. Drivers often notice that when starting the engine on a cold, a rattle is heard, something creaks in the engine, a whistle appears, etc.
We also recommend reading the article about what it means. From this article, you will learn about the various noises and knocks that pose a greater or lesser danger to the engine, as well as how to properly differentiate them in the self-diagnosis process.
It should be noted that usually many sounds are heard better at the moment of a cold start, although in some cases the noise does not go away even after the power unit has warmed up. It should also be added that in some cases the problem is noticeably progressing, that is, the sound increases each time or gradually. In other situations, extraneous noise may not change its tone and intensity for hundreds or even thousands of kilometers.
In this article, we will talk about what breakdowns can lead to the fact that noise is heard during a cold start of the engine, as well as how and by what additional signs you can determine the malfunction yourself.
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A rattle is heard when starting the engine
If the driver turns the ignition key to the "start" position and at that moment a rattle is heard, while the noise disappears after the engine "grabs" and starts to work on its own, then the most common cause is considered to be a starter malfunction.
If, when starting the engine, a starter rattle is heard on a cold or hot, then there may be several reasons for such a malfunction.
As a rule, it is necessary to check the solenoid relay, starter bendix and. The fact is that the bendix may not engage with the flywheel properly, as a result of which a crack is heard when the engine is started or a characteristic rattle of the starter appears.
Whistle is heard when starting the engine
The whistling sound at the time of starting is usually made by the alternator belt or (pump). The malfunction manifests itself in the form of a high-frequency squeak or squeal after starting the internal combustion engine, and can also make itself felt already on a warm engine when you sharply press the gas pedal and increase speed.
- In case of a problem with the belt, it is necessary to check its condition and tension. Sometimes it helps temporarily to apply special rubber care compounds that allow the surface of the belt to remain soft and supple, protect against cracking, etc. With a clear weakening of the tension, the alternator belt must be tightened, while checking the condition of the pulleys and tensioner in parallel. We add that it is not recommended to tighten a strongly stretched belt, since the whistle will appear again after a short period of time. In this case, and also when it is not possible to further tighten the alternator belt, only replacement is shown. If the belt is normally tensioned, does not slip on the pulleys, but still whistles, then it may be of poor quality and needs to be replaced.
We also add that the cause of the whistle can be not only the belt, but also the generator itself. More precisely, problems may arise with the bearings of its drive. This is indicated by the characteristic rustling, whistling, slight crackling while the engine is running at idle.
- The pump also emits a thin whistle at idle, the problem may be accompanied by a rumble or crackle. This feature is the reason for the mandatory check and replacement of this element.
To check the generator and / or pump, you can take a block of wood, you can also attach a tin can, etc. to the end of a wooden stick. Then one end of the bar or stick is applied to the drive area of the generator or pump with the engine running, and the other end of the bar or a tin fixed to the stick is brought to the ear. This solution allows you to more accurately determine the source of noise and localize the fault. By the way, if possible, instead of a home-made device for listening to noise, you can use the so-called car stethoscope (sometimes they use a medical one).
If the noise source is not fully installed, then it is necessary to remove the alternator belt, after which the pump or alternator pulley is turned sharply by hand. The appearance of noise, difficulty during rotation, beating, play and other abnormalities will indicate a problem. In the case of a generator, the device can be repaired by replacing the bearings. It is recommended to change the pump immediately, since on many cars the jamming of the water pump leads to a broken timing belt.
An additional reason for replacing the pump is considered to be the appearance of streaks at the place of its installation. Coolant leaks pose a danger in the form of overheating of the internal combustion engine, a break means that it hits, causing the valve to bend. In the end, if you ignore these problems, the motor may need an expensive or even.
Knocking sound when starting the engine
The appearance of a knock in the engine should be divided into problems with and elements of the internal combustion engine itself (and, pistons, crankshaft, etc.) Extraneous sounds in the timing area may indicate significant wear on the rollers, or belt defects.
The rollers may whistle, howl, crunch, or rattle. In some cases, the timing belt rubs over the protective cover. We also note that on motors with a chain, when the chain itself is stretched or the tension is insufficient, the sound resembles a rustling chirp, and pops can also be heard. If you increase the speed, such sounds disappear and appear again after releasing the gas. In this situation
A characteristic knock of the gas distribution mechanism is the knock of intake and / or exhaust valves. Such a knock differs in frequency from other knocks, has uniform intervals. The fact is that the camshaft rotates twice as slowly as the crankshaft. It can lead to knocking.
Why a cold engine can knock: various malfunctions. Analysis of the nature of the knock in the power unit: sonorous, metallic, muffled, etc.
Any extraneous sounds from under the hood during engine start or immediately after it are a serious reason for diagnosis. Grinding, creaking, whistling or knocking can be both signs of wear on elements such as drives, bearings, pulleys and belts, as well as a sign of a breakdown of the engine itself and its components.
PROBLEM rattle when turning ignition key
Cause : If the rattle is heard only at the moment the key is turned to the “start” position, and then the noise disappears and the engine starts to work as usual, the starter itself is most likely faulty.
Solution: check the operation of the solenoid relay, starter bendix and flywheel (the bendix must engage with the flywheel).
PROBLEM whistle sounds when starting the engine
Cause: A whistling sound at the time of starting the engine is usually associated with a malfunction of the alternator belt or the water pump of the cooling system (pump). The sound is high-frequency, very unpleasant - a search or a screech. It can occur not only at the time of starting, but also on a warm engine, when the driver abruptly squeezes out the gas, and the crankshaft speed jumps. If during the operation of the internal combustion engine at idle, rustling, whistling and slight crackling are heard, the reason may lie in the wear of the generator drive bearing.
Solution: check the condition of the alternator belt, whether it is well tensioned. You can try lubricating the surface of the belt with a special rubber care compound to give the belt more elasticity and prevent cracking. If the belt is loose, you need to tighten it, paying attention to the condition of the pulleys and tensioner. A severely stretched belt should be replaced.
A wooden block or stick will help diagnose a problem with the generator and pump. A tin can is tied to one end and brought to the ear. The free end of the bar (stick) must be attached to the junction of the generator or pump and the engine (the motor is running). Such a simple method will allow you to better listen to the malfunction and determine its localization. You can also use a car stethoscope for the same purpose. Some even use medical.
If the source of the noise cannot be identified, the alternator belt must be removed. Then the pulley of the pump or generator is turned sharply by hand. Noises, difficult rotation, beating, backlash and other deviations are a sign of a breakdown.
The generator can be repaired by replacing the bearings. It is better to change the pump immediately, without waiting for the timing belt to break.
PROBLEM knocking sound when starting engine
Cause: The problem is with the gas distribution mechanism, with the elements of the engine itself - the crank mechanism, the CPG, pistons, connecting rods, etc. Either wear of the rollers, defects in the timing drive - chain or belt.
Solution: Diagnose the sounds yourself, and then consult a specialist.
Rollers can make many different sounds - whistling, howling, crunching, tapping. When the timing chain is stretched, the sound is similar to a rustling chirp, muffled pops can be heard. Moreover, with an increase in speed, the sounds will disappear, and after releasing the gas, they will reappear.
Problems with the gas distribution mechanism are determined by the sound of valves. This is a very uniform muffled knock with a characteristic interval - after all, the camshaft rotates twice as slowly as the crankshaft. When the oil reaches the bearings, the knock disappears. The average is three seconds.
Causes of wear of the camshaft bearings and, in fact, knocks are extensive. This is bad or dirty oil, and its insufficient pressure, and scratches and minor defects in the camshaft itself.
You can still ride with such a malfunction (if there are no hydraulic lifters in the timing, which will cause accelerated wear and breakage of the part). But it’s not worth delaying the repair: the problematic camshaft will shift slightly until the gaps between it and the associated parts are broken. As a result, the valve opens slightly, compression drops, difficulties with starting and uniform engine operation, the threat of overheating and burnout of the piston and valves.
A loud knock, the same frequency as the knock of the camshaft, is a sign of improper valve operation. Usually caused by enlarged clearances. If the engine design involves a hydraulic compressor, the same knock indicates wear on the latter or insufficient filling with oil.
When starting the engine in a cold, when it is running in XX mode or at low speeds under load, the knock of the pistons can be recognized by a dull sound, as if someone is hitting pottery.
A metallic, slightly muffled sound indicates that the main or connecting rod bearings (plain bearings) of the crankshaft have worn out. In this case, after a sharp pressure on the gas in XX mode, the sound will increase, and with an increase in speed, its frequency will increase.
Sharp knocks at irregular intervals, especially audible with a smooth change in speed, are a sign of axial play of the crankshaft.
The knock of connecting rods in a diesel engine is a sign of a serious breakdown, and in no case should you drive such a motor. It is necessary to deliver the car to a service for subsequent repairs - crankshaft boring, replacement of connecting rod bearings, etc.
Why does the crankshaft knock at all?
There are enough reasons: over time, large gaps appear in the main or connecting rod bearings, the necks or liners wear out. Non-observance of the normal oil change interval, antifreeze leaks, fuel getting into the oil due to damage to the cylinder block gaskets, a drop in oil pressure, and even a trite clogged oil filter - all this can lead to crankshaft knocks on a diesel engine. There are cases when the crankshaft knocks even after a single trip with a critical oil level in the crankcase - we are talking about the so-called engine oil starvation.
Why else can there be noise in the engine compartment
- Separately, among the problems of extraneous sounds in the engine compartment, one can single out the situation of starting a diesel engine on a cold one.
- Strong vibration and a characteristic knock may also indicate a problem with the pillows that hold the internal combustion engine.
- The power steering pump, its drive or steering rack may make a screech, squeak, howl or whistle at the time the diesel engine is started.
- If the engine start is combined with the air conditioner on, the cause should also be looked for in the air conditioner compressor or in its drive.
- Due to the fact that in many cars the gearbox is located close to the engine in the engine compartment, it can be difficult to distinguish its noise from the noise of the engine. Most often, a dead release bearing is responsible for the rumble of the transmission.
- Another very dangerous sound that can hardly be confused with anything is the knocking sound of the engine, when a mini-explosion occurs as a result of improper combustion of the fuel mixture in the cylinder. The shock wave is reflected from the piston, destroying it. Indirect signs of diesel engine detonation are, in addition to a sharp metallic knock, engine tripping, a decrease in its power, and unstable operation.
Total
There are many reasons for the appearance of extraneous sounds in the engine compartment. For inexperienced drivers, determining the cause of knocking can be difficult. In any case, any metal knocks - metal on metal, clanging, grinding - a reason to abandon the trip and urgently go for diagnostics.
You can preliminarily determine the cause of the malfunction by paying attention to the nature of the sounds:
- engine knocking when starting "cold" or hot
- sound appears at low or high engine speeds
- is there any periodicity and rhythm in knocking
- whether the engine knocks with the same force, or the sounds intensify (subside)
- a loud or dull thud comes from under the hood.
For a number of very old engines with impressive mileage, the presence of certain noises is unavoidable. This is due to the development of a motor resource and the natural wear of parts - a camshaft, valve mechanism, etc. Such an engine can be operated, and repairs are most often not major.
Dangerous knocks include piston, connecting rod and crankshaft knocks. They talk about those breakdowns that destroy the engine, and an attempt to drive a car with a distinct metallic knock can lead to jamming of the internal combustion engine, after which it will become, in principle, unrepairable. Therefore, in these cases only tow truck and service station.
We also examined the causes of extraneous sounds from the engine compartment, which are not related to the operation of the internal combustion engine itself. We are talking about the noise of the timing drive, water pump, air conditioning compressor, power steering, flywheel and gearbox.
- How not to boil in the heat, if you have a diesel engine, read
- How to extend the life of your diesel engine, we wrote.
If you are looking for quality parts for your diesel engine, check out our catalog
Engine screeching at startup is quite common, especially for older cars. But, this malfunction did not bypass the new vehicles. The appearance of this problem is associated with the failure of one or more elements in the motor.
Causes of engine rattle
When starting the engine, a rattle is heard - this means that the starter does not catch. This problem is related to the bendix, retractor relay or flywheel. But if a crack is heard when starting the engine, then here the matter is much more complicated and the consequences can be more difficult - a malfunction in the piston mechanism or in the details of the cylinder head.
Methods for diagnosing and troubleshooting
Many motorists, leaving the house in the morning and starting the vehicle engine, were faced with the fact that rattle and crackling was heard during start-up. In this case, the malfunctions are different and it is worth understanding what sound, what it can mean.
Starter, flywheel and retractor
Perhaps it is worth starting the consideration with the fact that a rattle appears during the start-up of the power unit. As it was clarified earlier, the matter here is in the starter or flywheel. So, if the rattle is accompanied until the engine starts, then this is due to the wear of the bendix or the flywheel crown.
To be more precise, the teeth of one or the second element are worn out, and the part clings poorly to the part. Also, the case may be in the retractor relay, which does not fully pull the bendix, which does not grab the flywheel.
To eliminate the malfunction, it is necessary to dismantle the starter and inspect the condition of the bendix, namely its teeth. If there is a characteristic wear in the form of "licking" of the teeth, then it is recommended to replace the part. But, and that's not all. Also, since the starter has already been removed from the vehicle, it is worth checking the solenoid relay.
To do this, you just need to connect it to the on-board network of 12 volts and listen to see if the retractor relay clicks. If clicks are not heard, then you will have to disassemble the starter and replace the failed part.
Also, this malfunction and the rattle effect can be caused by the fact that the flywheel crown has worn out. It is worth noting that not all engines have a collapsible flywheel, so the entire assembly often changes. Thus, the wear of the teeth leads to the fact that the bendix cannot catch on them and turn the crankshaft. It is at this moment that a rattle occurs in the engine compartment.
Crack - where to run and what to do
Crack is a malfunction in the crank mechanism or cylinder head. So, first of all, it is worth checking the cylinder head. Faults must be sought in the guide bushings, where wear could have occurred, and the valve simply dangles, and hydraulic compensators can also knock and crack, which should be changed, since they have exhausted their resource.
The second place to pay attention to is the cylinder block and its elements. So, cracking can be caused by a lack of lubrication (engine oil), as a result of which the oil scraper rings scratch the cylinder walls. Also, special attention should be paid to the main and connecting rod bearings, which can rotate due to wear on the part of the block itself.
In this case, special attention should be paid to the condition of the crankshaft, on which scratches and deep grooves could form.
The last element that can also cause cracking and damage to the cylinder walls are the connecting rod bushings. They could loosen up and go beyond the pressing aisles. In this case, the danger is that the bushings can damage the cylinder walls so much that the only way out is to liner the block or replace it.
Conclusion
Rattle and crackle in the power unit indicate that some parts of the motor are out of order. So, the rattle is accompanied by a malfunction in the starter or flywheel. As for the cod, the situation is much more complicated - most likely the problem lies in the crank mechanism or in the cylinder head.
Starter necessary for every car - this small device starts the engine, without which, for obvious reasons, movement is impossible. At the same time, the starter serves a rather short period, rarely exceeding six to seven years, after which it requires a complete replacement with a new one, as a result of wear. But even during six years of operation the starter is prone to minor breakdowns and malfunctions which you can fix on your own.
Starter repair with serious damage, it is better to provide specialized car services, which today there are a fairly large number.
One of the symptoms of a starter malfunction can be a sharp unpleasant sound during start-up, which is similar to a mechanical rattle - there can be quite a few reasons for this phenomenon, but the main one is starter gear failure.
During operation, the teeth of the starter gear wear out - scratches appear on them, they bend and gradually fail - by itself, a gear with bent teeth cannot function normally.
To eliminate such a malfunction is simple - you just need to disassemble the starter and, having pulled out the gear, replace it with a new one. Bendix- one of the most inexpensive starter parts, but not timely replacement of this part can hit your pocket hard. Quite often, due to gear wear, the bendix cannot disengage from the flywheel, and the starter continues to work with the engine until the device is completely destroyed. It will not work to set bent teeth with the help of improvised means - a hammer or pliers that every ordinary motorist has in their arsenal, so it's better not to try, but simply replace the bendix with a new one.
The next reason for the rattle may lie in the buffer spring - this is the most common reason why car starter repair- the spring weakens its tension over time and the bendix does not come out completely, thus creating proper engagement with the car's flywheel. The only way out of this situation is its complete replacement, which can be done both independently and in a car service. Work of this kind is not expensive.
The last reason for such a malfunction lies in the adjustment of the gear stroke itself, which can only be corrected in a car service, with the help of qualified professionals with the appropriate education and work experience. In addition, the incomplete output of the bendix can be caused by wear on the plug of the retractor relay, and it is rather difficult to find this part in retail.
You should always remember that if you are not sure that you can independently carry out a quality repair of a faulty part, it is better not to undertake it. It is quite possible that you will only make it worse, the final repair can be much more expensive.
Often drivers are interested in why a crackling and rattle is heard when the engine is started. There may be several reasons for this phenomenon. In any case, the source of this sound should be eliminated as soon as possible. Otherwise, you risk getting a breakdown at the most inopportune moment. In general, when any strange sounds appear, you should check their origin. After all, this is just a sign of a breakdown.
The sooner you eliminate it, the better. After all, most of the malfunctions can cause a chain reaction. And provoke breakdowns of other elements of the engine. Therefore, always listen carefully to the operation of the power unit.
Causes
Why is there a crackling sound when starting the engine? This question is often asked by beginners and not so motorists. Many are frightened by an incomprehensible sound heard when starting the engine. Although in many cases this is not a difficult problem. But it still needs to be fixed, and for this it’s good to know where to look for the problem. There are several places that give out crackling and grinding at startup:
- Starter;
- Flywheel;
- Roller mounting bolt (timing).
Starter
There are several reasons for this behaviour. In order to understand the reasons in more detail, you need to know the starter device and the principle of operation. It consists of an electric motor, on the shaft of which an overrunning clutch with a drive gear is installed. In everyday life, the clutch and gear are called - bendix. Also in the design there is a starting relay with a solenoid. This design is referred to as a "traction relay". It is connected to the clutch by the starter lever.
This construction works as follows. When turned on, the electric motor starts to turn the bendix. At the same time, the traction relay, having actuated, moves the overrunning clutch forward with the help of a lever.
As a result, the gear engages with the teeth of the flywheel and spins the engine. After the engine is started, the overrunning clutch is activated. This prevents the starter from being damaged. When the power supply to the device is turned off, the relay stops working and returns to its original position. Passenger car starters typically use a roller type overrunning clutch.
There is only one reason for the rattle at startup. For some reason, the bendix cannot fully engage the flywheel. Therefore, when starting the starter, a gnash of slipping teeth occurs. This problem needs to be fixed as soon as possible. Otherwise, the flywheel and starter gears may be damaged. You need to check the following points:
- First, check the starter mount. Sometimes vibration can loosen the mounting bolts. In this case, the starter warps and the gear loses full contact with the flywheel. In any case, remove the starter and check the condition of the bendix;
- Sometimes gear wear can be the cause of problems. In this case, the efficiency of the starter is reduced. When starting the engine, the rattle of the bypassing Bendix will be heard. Over time, the starter will not be able to turn the flywheel at all. After removing the part from the machine, you can see the gear wear with the naked eye;
- Sometimes the bendix does not walk well on the shaft and simply does not reach the flywheel. In that case, remove it. It is necessary to anoint the shaft with any engine oil (or whatever is at hand). Also check the operation of the traction relay.
Cracking at start can also occur due to problems with the power supply to the starter. It appears when the positive wire is loosened. With poor contact, a spark discharge occurs, which then produces a crack. Check wire. Tighten if necessary.
Flywheel. The cause of the rattle may be in the engine. With a lot of wear on the flywheel teeth, they cannot form full contact with the starter gear. As a result, you can hear an unpleasant rattle. It is advisable to replace the flywheel. Otherwise, the wear of the bendix will increase and you will have to change it regularly.
Since we are talking about the flywheel, read our two articles on this topic.
