Hello, dear friends! I propose to discuss with me today such a topic as valve knocking on a hot engine. You probably know what a timing belt is, what this abbreviation means and what purposes the gas distribution mechanism serves.
One of the key components of the timing belt is the valve. In addition to valves, the assembly contains pushers, hydraulic compensators, rocker arms, hoses, etc. Also, do not forget about the camshaft, or simply camshaft. It is he who is responsible for ensuring that each of the timing elements works correctly.
The essence of the mechanism is that the shaft rotates and actively interacts with its cams with the pushers. The latter rises along with the so-called barbell. The upper edge of the rod acts by pressing on the rocker arm. It, in turn, as it rotates, opens groups of intake and exhaust valves located in the cylinder head.
At the same time, in a car or motorcycle, motorists may notice how the valves begin to knock on a warm and hot engine. You need to know the possible causes and further actions on the part of the car owner.
Sign of severe valve wear
True, as the working resource is exhausted, this picture gradually changes for the worse. Miracles do not happen, and thoroughly worn-out metal parts begin to rumble, rumble and tinkle more clearly and frighteningly.
- Such changes in the functioning of the engine are signs of increasing valve damage.
- In this material we will talk about the reasons for the knocking of valves in the engine and what needs to be done to put an end to this alarming phenomenon.
Let's sum it up
The appearance of valve knocking indicates the need to quickly solve this problem. In addition to increasing the gap, the causes of increased noise may be:
- worn camshaft cams;
- broken valve spring;
- there is a defect in the valve guide;
- the timing belt/chain has become loose;
- there is a decrease in the efficiency of lubricant supply through the camshaft channels to the valve stems;
- there were problems with fixing the camshaft;
For high-quality repairs, you will need to disassemble the engine (remove the valve cover or cylinder head), after which the camshaft and other timing elements are repaired. Let us add that timely professional adjustment of valves can significantly increase the life of the gas distribution mechanism and the internal combustion engine itself.
Source
The characteristic ringing sound of breaking valves
It can be very difficult for inexperienced car enthusiasts to identify by the nature of the sound alone the segment of the power plant that has begun to operate abnormally.
There are too many components and assemblies in a modern car, and only a driver who has covered hundreds of thousands of kilometers can study all the details of their functioning in the event of severe wear and tear.
At the same time, knocking valves stand out somewhat from the background of other failing mechanisms. The valves make a ringing sound, reminiscent of an iron rod hitting a rail. This noise comes from the timing belt area.
It is important to note that a drop or increase in engine speed does not in any way affect the intensity of this sound.
Typical causes of ringing “fingers” during normal operation of the internal combustion engine
If the “fingers” knock during acceleration in the Kalina, the mass air flow sensor may have failed. If it is not working correctly, then the ECU will receive incorrect information and issue incorrect commands. Another reason is an incorrectly set ignition timing. For this reason, the point at which the fuel will burn maximum is approaching TDC. This leads to increased pressure in the combustion chamber. If the “fingers” knock when accelerating on a Ford Focus, then the knock damping sensor may have failed. It's definitely worth checking this item. If it stops working, it should be replaced.
Difficulty identifying specific valve problems
If the car enthusiast is able to accurately recognize that the knocking noise is coming directly from the area where the valves are located, then only those who have extensive experience in engine repairs, including major ones, will be able to identify the specific cause of this malfunction.
With all this, even a novice motorist can use a clear scheme for finding the source of problems, thanks to which it is possible to almost accurately indicate the problem that caused the knocking.
Algorithm of diagnostic procedures
The sequence of operations in this case is as follows:
- You should lift the hood and unscrew the cap on the neck into which the engine oil is poured;
- Next you need to listen to the operation of the motor. Typically, an increase in the intensity of the knocking noise when the cover is removed definitely indicates that the valves are the root cause of the observed problems;
- A stethoscope, which must be placed in close proximity to the likely source of mechanical problems, will provide additional clarity in diagnosing such problems.
“Fingers” knock during acceleration: the main reasons. Troubleshooting rules
Any extraneous noise in a car engine often makes owners feel wary. And even if these sounds do not affect driving performance in any way, their very appearance makes the driver think about diagnostics. Many cars have knocking pins when accelerating, but this problem is often ignored. The sound appears when the car picks up speed. If you do not pay attention to this in time, much more serious problems arise. At the same time, car enthusiasts cannot determine the reasons for the appearance of knocking noises, nor can they fix this problem on their own. Let's look at the reasons for these sounds that are unpleasant to the driver's ear, and also find out how to fix these problems with the engine.
Top 5 causes of valve knocking
The most common reasons why valves begin to annoy and make strange sounds are as follows:
- The size of the technological gap that should separate the pushers from the valves changes. During assembly of the machine on the conveyor, this gap is fine-tuned. If, as a result of long-term operation of the engine, this gap goes beyond the permissible limits, a characteristic knock with metallic notes inevitably follows.
- Knocking in the valve area is a consequence of purchasing cheap, low-quality fuel. The price for such savings is engine problems. In order to prevent them, you should strictly follow the instructions for selecting fuel given in the vehicle documentation. In the worst case scenario, so-called engine detonation may well occur. This destructive process will inevitably affect the performance of the valve system.
- It often happens that the valves start knocking only when accelerating or when driving very fast. This is a consequence of a decrease in oil pressure in the lubricating motor units.
- When a knocking noise makes itself felt after updating the timing belt, it means that the pulley was installed incorrectly. As a result, it works abnormally, which leads to misadjustment of the valve mechanism.
- The most common causes of knocking include banal wear of valves after the car has traveled a certain mileage. In this case, the factory resource is exhausted, and the only effective way to solve this issue is to completely update the worn parts.
Engine breakdown after gap expansion
Practice shows that the main reason for valve knocking is misadjustment of the gap, which separates the cams on the camshaft and the levers.
- If the gap exceeds the normal parameters, it results in the knock of the cam on the rocker.
- This sound is somewhat reminiscent of the iron clanking made by a hammer and chisel.
Due to the expansion of the gap, rapid depreciation of the power plant occurs, which is fraught with destructive phenomena for the engine.
For a number of models, this gap has the same dimensions, but in some cases engineers set a unique parameter.
Clamping and incomplete closure of the valve
It is important to note that narrowing the gap also adversely affects the functioning of the valve mechanism. With this development of events, there is a risk of clamping the valve, and later incomplete closure will become the order of things.
Continued use of the engine with insufficiently closed valves will lead to a drop in compression and excessive heating of the engine.
The need to periodically adjust the gap
If in such a situation you do not take timely measures to maintain and restore the valve system, then you should expect one hundred percent failure of the cylinders.
- Moreover, it is not at all a fact that only some of them will stop functioning, since failure often occurs in the entire cylinder block at once.
- In order not to find yourself in such a deplorable situation, the way out of which will be an expensive call to a tow truck and ruinous major repairs, you need to regularly check the width of the gaps and, if necessary, correct it.
A car usually needs such a service after every fifteen thousand kilometers.
What's wrong with them
Now we will describe common reasons explaining why valves knock. In modern engines, the camshaft is located on top, its cams push the valves through rods - a simple, best mechanism. The rods are called pushers.
- There is always a minimum gap between the tip of the pusher and the cam, regulated by the manufacturer. An increase in the gap is one of the reasons why the valves began to knock. As the gap decreases, knocking will also appear, and the valve may eventually stop closing tightly.
- Another possible cause of monotonous valve song could be a knocking engine, for example, due to bad gasoline.
- If valves knock only during acceleration, this is most likely due to increased engine speed and insufficient oil pressure.
- The malfunction may occur due to a poorly tensioned timing belt.
- Finally, it is simply wear of parts or shaft cams.
With all this, it is necessary to distinguish between two main types of the problem being analyzed. Valve knocking sometimes occurs only on a cold engine or, on the contrary, only on a warm one. Let's look at these varieties separately.
If the valves knock only when cold, then the essence of the phenomenon is as follows:
- the engine is a bit old, worn parts show themselves with large gaps when starting up, gradually, when warming up, the iron expands, the gaps decrease, the sound disappears, this is the main answer to the question why valves knock only on a cold engine;
- The gap between the pusher and the cam is no longer normal, but on a warm engine it still does not produce an extraneous sound.
If the problems with the valves are only hot, then the possible prerequisites are as follows:
- the bolt securing the camshaft to the bed is not tightened well; when warming up, the cam seems to move away from the pusher;
- insufficient oil level in the engine, severely clogged oil filter - because of the latter, for example, there is no longer enough oil for the valves when it’s hot;
- hydraulic compensators are knocking.
About hydraulic compensators and more
Let's talk about them separately now. If they are not there, for example, when a VAZ 2109 (which does not have them) has a valve knocking somewhere, then the last reason from the above list immediately disappears... So, if they are not there, the valve clearances are adjusted using special washers, and if they are there are... They perform a self-regulatory function.
In general, a hydraulic compensator includes a housing and a plunger. Both are located just between the cam and the valve. When the cam moves, oil from the engine enters the housing, pushing out the plunger. It fills the entire thermal gap between the cam and the end of the valve stem when the valve opens, and when it closes, the oil leaves. This solves the problem.
