What to do if a hydro-compensator knocks

What to do if hydro-compensators knock?

What to do if the hydro-compensators knock Among the possible problems that may arise with the engine, even a new car, is a knock hydro-compensators. Moreover, the knocking of hydro-compensators does not yet mean a malfunction of this part, the reasons for this may be very many. Therefore today we will talk about why hydro-compensators knock, and what should be done about it?

The knocking of hydro-compensators can be traced both on a cold engine, and on a warmed up engine, depending on the cause. It is worth noting that in any case, this should not be left alone. When hydrocompensators knock, the service life of the cylinder-head is significantly reduced and the risk of malfunctions increases. Now let’s look at the causes of what may be causing the knocking. How do you determine which hydrodynamic expansion joint is knocking?

To check the tappets, you need to press on it with a soft metal mallet or a screwdriver (with the camshaft cam should be turned to the tappet “back of the head”). In its normal state, the hydraulic tappet should be squeezed with a considerable force. If the force is low, the hydraulic tappet must be replaced. Install the cams of the camshaft one after the other with the tabs facing upward and check for clearance between the tappets and cams. By pushing in (e.g. with a wooden wedge) the hydraulic tappet to be checked, compare its speed with that of the others. If there is a gap or increased speed, disassemble the tappets and clean the components from dirt or replace the tappets. Knocking at the expansion joints when they are hot

The simplest and most common cause of a knocking sonic taps is poor quality oil. Yes, if the oil has not been changed for a long time, or is of poor quality, the first thing that will respond will be the hydrodistributors. If you just change the oil, the problem will disappear at once.

A dirty oil filter may also be the cause of the hydro-compensator knocking. The oil simply won’t flow to the tappets under the necessary pressure, which will cause them to knock. The problem can also be solved very easily, just by replacing the filter with a new one.

The problem with the knocking of the tappets can also be found in the oil pump. If it does not create the necessary pressure, the oil simply will not flow to the pressure regulators.

If the oil flows through the gap between the plunger and the sealing sleeve, which has increased due to wear, replace the worn out timing belt assemblies.

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Finally, the cause of the knocking may also be a defect in the hydrodynamic expansion joint itself. A knocking of the timing belt when cold

A hydro-compensator knock may also occur when the engine is cold, i.e. disappear as the engine warms up. There may be several reasons for this phenomenon, too.

One of the causes of hydro-compensator knocking in a cold engine can be contamination of its channels. The fact is that cold oil has the same viscosity, which does not allow it to penetrate a clogged channel. When heated, becoming more liquid, the oil is already able to penetrate into the tappets and, accordingly, the knock will disappear.

In addition, the cause may be, again, in the oil. If the oil is too viscous, you will hear a knocking when the engine is cold. When it becomes more fluid as it warms up, the knocking will disappear.

Finally, the problem could be a hydro-compensator valve. If it does not hold the oil and blows it out when the engine is off, it is quite logical that a knock will be heard when starting the engine, until it is warmed up.

The hydro-compensators knock at high rpm, and there is no knock at low rpm:

The cause of the malfunction is foaming with excess oil (above the upper mark on the dipstick) in the oil sump due to it being churned by the crankshaft. Air-foam oil mixture getting into the expansion joints will disturb them. Air intake from oil pump due to excessively low oil level in oil sump. Damage of the oil receiver due to deformation of the oil sump when impact on a road obstacle.

How to fix – bring the oil level in the oil sump to normal. Bring the oil level in the oil sump to normal. Repair or replace defective parts. Constant noise of one or more valves, independent of crankshaft speed:

The cause of the malfunction is a gap between the tappet and cam of the camshaft due to damaged or contaminated hydro-compensator parts.

Remove the cylinder-head cover, install the camshaft cams one after the other with the tabs facing upward and check the clearance between the tappets and cams. By pushing in (e.g. with a wooden wedge) the hydraulic tappet to be checked, compare the speed of its movement with the others. If there is a gap or increased speed, disassemble the tappets and clean the parts from dirt or replace the tappets.

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Don’t rush to disassemble the engine and look for the reason, try just to replace the filter and oil with one recommended by the manufacturer.

In principle, the knocking of hydro-compensators is not an abrupt phenomenon. It begins to appear gradually, more and more reminding. So if you have noticed, that hydro-compensators in your car began to knock, do not panic. It is quite possible to drive for a while, but it is better not to delay with the repair. If you do not pay attention to the knocking of hydro-compensators, there is a risk of damaging the cylinder head.

A knocking of hydro-compensators when warm

The most frequently the knocking of hydro-compensators while hot is caused by low-quality or old engine oil, a clogged oil filter, poor performance of the oil pump, insufficient oil quantity, or a mechanical breakage. Accordingly, the first thing to do when they knock is to check the engine oil level and condition, as well as the oil filter. A faulty or clogged filter prevents oil from circulating through the oil channels.

Knocking at the expansion joints when hot

Usually, the hydro-compensators (in common parlance – hydraulics) first start banging exactly “when they are hot”. If the hydraulics are jammed or the oil channels are clogged in them, they will start knocking immediately, and after warming up, the sound may subside, since they do not get the necessary amount of lubrication. In this case only their replacement will help. But, when the knocking occurs a few minutes after starting and warming up the engine, the problem can be solved easier, if the cause is not in the oil pump.

Signs of hydro-compensator knocking in the hot

It is very important for the motorist to know how to understand that one or more hydrocompensators knock. After all, its knock can easily be confused with other sounds of problems with the piston pin, crankshaft liners, camshaft or other parts inside the engine.

A hydro-compensator knock when the engine is hot can be diagnosed by opening the hood. The sounds will start coming from under the valve cover. The tone of the sound is specific, characteristic of metal parts hitting each other. Some people compare it to the sound made by a chirping grasshopper. What is characteristic – the knocking from defective expansion joints occurs twice as often as the engine speed. Accordingly, with the increase or decrease of engine rpm, the sound of knocking from the expansion joints will behave accordingly. Under a throttle reset, you will hear sounds like your valves are out of adjustment.

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Causes of knocking of the expansion joints on hot

In most cases, there can be one of two reasons why the expansion joints bang when warm – too little viscosity of the warmed oil, or insufficient oil pressure. There can be a variety of reasons for this.

  • Low oil level. This is a very common reason why the expansion joints bang when hot. If there is not enough lubricating fluid in the crankcase, there is a high probability that the expansion joints will run “dry”, without oil, and, accordingly, will knock. However, it is harmful for the tappets also too much oil. In this case a foaming of lubricating fluid occurs that leads to clogging of the system, and as a consequence, incorrect work of expansion joints.
  • Clogged oil filter. If this element has not been changed for a long time, over time it becomes clogged with dirt, which prevents the normal oil flow through the system.
  • Improperly chosen viscosity . Often motorists are interested in the question of why hydro-compensators knock on hot after oil change. In most cases, the problem is just because of wrong oil viscosity or poor quality oil. There is no such a thing, that some oil likes hydro-compensators, and some does not, you just need to choose it correctly. If the oil is too thin, you may not have enough pressure to completely fill the hydraulics. And when it is of poor quality, it simply quickly loses its operational properties. Changing the oil will help solve the problem, and don’t forget to change the oil filter along with the oil.
  • Defective oil pump . As a rule this reason is typical for cars with high mileage, where the pump is simply worn out and unable to create the proper pressure in the engine lubrication system.
  • Use of oil additives . Most oil additives perform two functions – they change oil viscosity (reduce or increase it), as well as change the temperature mode of the oil. In the first case, if the additive has lowered oil viscosity, and hydro-compensators are already sufficiently worn, then just the conditions arise, when the hydraulics knock on a hot engine. As for the temperature mode, the oil works optimally when it is “hot”, and the additive can change this property. Accordingly, after pouring the additive into the oil, the expansion joints may knock when there is not enough pressure to press the oil into them. Usually because the oil is too thin.

What to do if the expansion joints knock when hot

The only way to get rid of the knocking is to find and eliminate its cause. Further will depend on the situation.

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First you need to check the oil level in the crankcase. It will determine how it will circulate through the oil channels. It’s also worth checking that the oil pressure is sufficient, even if the oil light isn’t on.

The wrong level and pressure of the engine oil will affect not only the operation of hydro-compensators, but also the work of the engine as a whole!

In every engine the working pressure of oil depends on its construction (it is necessary to specify in the documentation), however it is considered that at idle revolutions the pressure should be about 1,6 … 2,0 bar. At high rpm it should be up to 5…7 bar. If you don’t have such pressure check oil pump. Most likely due to oil liquefaction its efficiency is reduced. Often the cause is not eliminated to provide pressure, at the knocking of scrollers in hot conditions the motorists drink thicker oil. But you should not overdo it, as too thick oil is hard to pump through the system. As a result, oil starvation may occur!

And do not be in a hurry to judge the pump itself. Faulty oil pump can be caused by different reasons – worn parts, faulty reducing valve, worn working surfaces of the parts, and also its work can worsen with an elementary clogging of oil intake grid. You can see if there is no dirt on the screen by removing the sump. But, even with such work, you should not hurry. It can get dirty only if the overall condition of the oil is bad, or an unsuccessful cleaning of the oil system has been made.

Check the condition of the oil . Even if you change it according to the regulations, it could be out of order earlier (under severe machine operating conditions or you got a fake). If you find a deposit and slag, it is often unclear what to do if hydro-compensators knock on hot. It is advisable to flush the oil system, because most likely the oil ducts can get clogged. To check the condition of oil it is enough to make a small drop test.

Most often, the problem is solved elementary – just change the oil and the oil filter. Or it is simply time to change the hydro-compensators.

How to check the hydrodynamic taps

You can check the hydrocompensators by one of three methods:

  1. Using a car stethoscope . However, this method is suitable only for experienced motorists who know how to “listen” to the engine. By applying it to the different areas of the hydro-compensators, you can compare the sounds coming from there.
  2. With the help of test probes . For this purpose special test dipsticks with a thickness of 0.1 to 0.5 mm are needed. Accordingly, on a hot engine, you must use the feeler gauges to check the distance between the compensator and the cam. If the corresponding distance is more than 0.5 mm or less than 0.1 mm, the hydrator to be checked is unsuitable and has to be replaced.
  3. The indentation method . This is the simplest and most common test method. However, to perform it, the hydro-compensators must be removed from the engine. After that, you must try to push the central rod of the compensator inside with a wooden bar or screwdriver. If an expansion joint is operational and is in more or less normal condition – you can hardly press it with a finger. And vice versa, the rod of a defective compensator will easily fall inside.
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The last method of testing can also be performed without removing the scrolls from the engine, however it will not be as convenient to do and the result will not be as obvious. Usually, failed hydrocompensators are replaced with new ones, but in rare cases you can try to restore it by flushing. Another option is to clean and repair the hydrocompensator. Practice shows that repairing and cleaning the Hydraulic Compensator does not often help, but it is still worth trying to repair it. When you decide to replace it, it is better to replace the whole set, otherwise the situation will repeat soon, but with other hydraulics.

If you drive with knocking hydro-compensators from 6 months and longer, then when you take off the valve cover, there is a high probability that on the “bed” of the camshaft, from the bottom, there will be burrs from rockers (rocker arms). Consequently, whether it is possible to drive with a knocking of expansion joints is up to you to decide.


The first thing to do upon occurrence of hydro-compensator knock is to check the level and condition of engine oil. At the same time, you should also check the oil filter. Often changing the oil together with the filter saves from a knock, and preferably with flushing oil. If change of oil does not help, the problem is most likely in the oil pump, or in expansion joints.

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