How to check the valve?

If exposed to temperaturemetal parts, then this necessarily leads to their expansion. The influence of the temperature factor is constantly exposed to the details of the gas distribution mechanism in internal combustion engines. To compensate for this effect, the designers of automobile engines provide a thermal gap between the cams of the camshaft and the valves. How can I check the valves for setting the thermal gap and how can they be checked for leaks? You will learn about this from our article.

How to check the correctness of the thermal gap

To carry out this work you will need two probes (0.2 mm and 0.35 mm) and wrenches.

  • If the gap between the valves and the distributorshaft is set correctly, the engine is running in a stable mode, since this process is not difficult at all. In those cases when there are extraneous noises when the engine is idling, which disappears if the crankshaft speed is increased, then it's time to check the gaps between the valve rods and the camshaft cams.
  • Check the necessary parameters only on a cooled engine.
  • Before you check the valves on the cold engine, you need to remove the valve cover, which is located on the cylinder head.
  • After that, the crankshaft must be installedat the top dead center of the first cylinder. The reference point in this case is the "slider" of the interrupter-distributor. It will need to show the direction towards the contact terminal of the first cylinder.
  • If everything is set correctly, then both valves of the first cylinder must be completely closed. Check the intake valve gap with a feeler gauge of 0.2 mm, and check the outlet clearance with a feeler gauge of 0.35 mm.
  • A large clearance of the exhaust valve, in comparison withinduction, is not accidental at all. The fact is that the exhaust gases leaving the exhaust valve have a high temperature, which heats up this part more. And this, contributes to a greater expansion of the valve.
  • How to check the valves of the second cylinder? For this, the crankshaft must be turned 180 degrees. After that, in exactly the same way, the gaps of the inlet and outlet valves from the second cylinder are checked.
  • Similarly, the valves are checked at the third and fourth cylinders.
  • If you find inappropriate gaps between the camshaft cam and the valves, then adjust them.

How to check the tightness of valves

Normal operation of the car in many respectsdepends on the correct operation of the gas distribution system. A key role in this is assigned to the exhaust and intake valves. They must have a snug fit on the cylinder head to their seats. Only in this case, the necessary pressure will be created in the combustion chamber.

  • Before checking the tightness of the valves withtheir saddles, it is necessary to remove the cylinder head (cylinder head). Clean it and the bearing housing from dirt and carbon deposits, remove deposits from the combustion chamber with a metal brush, and wash oil deposits on it.
  • Carefully inspect the bearing housing andthe cylinder head. They should not have cracks and be whole. It is necessary to inspect the working surfaces of the bearing housing, the camshaft bearings and the wall at the mounting holes of the hydropushers. On them there should be no traces of metal and scuffing. The valve guides and seats must sit tightly in the cylinder head. Do not allow their displacement during the operation of the gas distribution mechanism. Valves and saddles should not have cracks and traces of burn-out.
  • Check the flatness of the cylinder head with a special template. If it is not available, this can be done with a wide-angle locksmith. It is applied diagonally with an edge to the lower base of the block head. Make sure that there is no gap between the edge of the ruler and the plane. It can be either in the middle part of the plane or along its edges. For both diagonals, the gap is measured with flat probes. 0.1 mm is the maximum allowable value for the gap. For large gap values, the bogie plane is milled or replaced.
  • Check the tightness of the cylinder head. To do this, the coolant supply window to the thermostat located on its end surface is muffled. After this, turn the head to fill with the kerosene of its internal cooling jacket.
  • It should be ensured that there are no kerosene leaks from the cylinder head. If you find it, then the head of the block, either repaired with cold welding, or replaced with a new one.
  • How to check the tightness of the cylinder head valves? To do this, the head of the block must be placed on a horizontal surface, so that the bogie plane is at the top. Then the combustion chambers of the cylinder head are filled with kerosene. Then it is necessary to wait 10 minutes. If the liquid level has decreased, this means that one or both valves are leaking.
  • The leakage of valves is eliminated bytheir lapping to the saddle. But this is the case if there are no mechanical damages and cracks on the valve plate and on the valve itself. To carry out this work, the oil-removal cap is removed from the valve. A valve is pulled out of the guide bushing. Lapping paste is applied to the working surface of the valve. Most often apply "Diamond". The valve is installed in the head of the unit, and a lapping device is fixed on its shaft.
  • The valve is pressed against the seat and turned fromside to side. After 12-15 turns, it is rotated 90 degrees and the process continues. Lapping is carried out until a uniform surface is formed on the valve plate and the seat, and a smooth layer of paste having a characteristic color should appear on the working surface. The remains of the lapping paste will need to be removed from both elements. The valve is replaced in the reverse order, and the oil removable caps are replaced.

Keep in mind that lapping is needed more forquality control of the interface itself, than for processing. If you wipe dry ground surfaces, and then turn the valve several times in both directions and simultaneously press it to the saddle, then on the facets of the parts should appear a shiny line. If it turned out to be closed, that is, it runs along the entire circumference - this will mean that the fitting of the parts is good, and you did everything right.

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