Removal and disassembly of the engine cylinder head is discussed in the relevant articles.

After dismantling the cylinder head, you need to rinse all the parts of the head, clean them from carbon deposits.

We prepare parts for inspection.

We check the seating surface of the head and the height of the cylinder head.

Ремонт головки блока цилиндров двигателя К4М

Высота h головки блока должна составлять 137 мм (рисунок 1).

Ремонт головки блока цилиндров двигателя К4М

Using a ruler and a dipstick, we check the flatness of the cylinder head seating surfaces (Figure 2).

Maximum flatness of 0.05 mm is allowed. Surface grinding is not allowed.

Ремонт головки блока цилиндров двигателя К4М

We check the cylinder head (no cracks and through corrosion) using an appropriate tool (Figure 3).

We check the length of the head mounting bolts. The length of the bolts, excluding the head, should be no more than 117.7 mm.

If we install new bolts, then they do not need to be lubricated before installing them, used bolts should be lubricated with engine oil.

Subsequent tightening of the cylinder head bolts is not required and is not allowed, otherwise the probability of the bolts breaking when unscrewing sharply increases.

Before tightening the bolts, remove any dirt and oil that remains in the threaded holes of the cylinder block.

Ремонт головки блока цилиндров двигателя К4М

We measure the thickness of the gasket (Figure 4). The thickness is measured at the location indicated by the arrow in Figure 4.

The thickness of the new gasket should be 0.96 ± 0.06 mm; the thickness of the crimped spacer shall be 0.90 ± 0.02 mm.

Ремонт головки блока цилиндров двигателя К4М

We inspect the hydraulic pushers and rocker arms.

We measure the valves in accordance with Figure 6. The dimensions of the valves must correspond to the data in the table.

Ремонт головки блока цилиндров двигателя К4М

Main valve dimensions

Description Size mm.

Bar diameter D1

Intake valves 5,470-5,485 *

Exhaust valves 5.456-5.471 *

Head diameter D2

Intake valves 32.70 ± 0.12

Exhaust valves 27.96 ± 0.12

Valve length L

Intake valves 109.32

Exhaust valves 107.64

Working chamfer angle A:

Inlet valves 45˚ 45 '

Exhaust valves 45˚

Minimum thickness of the cylindrical shoulder of the valve disc T

Intake valves 1.15

Outlet valves 1.27

Valve stroke

Intake valves 9.221

Exhaust valves 8.075

* the diameter D1 of the valve stem is measured at a distance of X1

Intake valves X1 = 75.14 ± 0.35 mm;

exhaust valves X1 = 77.5 ± 0.35 mm;

Valve guides

Ремонт головки блока цилиндров двигателя К4М

The slope of the intake valve guide is 63˚30 '(figure 7).

The inclination of the exhaust valve guide is 66 °.

The height of the protruding part of the valve guide H for inlet and outlet valves is 11 ± 0.15 mm.

Valve stem seals

The valve stem seals are removed using tool Mot. 1335.

The valve stem seals are fitted with tool Mot. 1511.

The valve stem seals must not be lubricated before installation.

Install the valve stem seals as shown in Figure 8.

Ремонт головки блока цилиндров двигателя К4М

- Insert the valve into the cylinder head.

- Fit the tip of tool Mot. 1511 onto the valve stem (the inside diameter of the tip must be the same as the stem diameter) (see figure 8).

- Press the valve against the seat.

- Place a non-lubricated valve stem seal onto the handpiece.

- Advance the valve stem seal by pushing it through the tip.

- Remove the tip.

- Place a mandrel on the valve stem seal. The inner diameter of the mandrel must match the diameter of the valve stem.

In addition, the lower part of the mandrel should partially abut against the valve stem seal, along the surface that supports the valve spring washer.

- Gently press on the valve stem by tapping the top of the mandrel with your palm until the valve stem contacts the cylinder head (see E, Fig. 8).

- Repeat the above steps for all valves.

Checking valve springs

Spring defects are shown in Figure 9.

Ремонт головки блока цилиндров двигателя К4М

In case of deformations B and C, the operation of the spring is permissible if the deviation from the vertical is not more than 1.2 mm; in case of loss of shape (D), the spring must be replaced.

Even if the shape of the spring is maintained, it is necessary to check its mechanical properties (height under a certain load). Only after such a check is the suitability of the spring for further work determined (see the table).

Valve spring parameters

Parameter mm

Free height 41.30

Spring height in working condition 23.20

Inner diameter 18.80 ± 0.20

Outside diameter 27 ± 0.2

Wire section - Oval

Height / under load

34.50 / 180-200

24.50 / 563-617

If a new spring is available, its performance can be compared with that of the old springs.

Install the new and old springs one after the other through the washers onto the long bolt.

Tighten the bolt nut so that the height of the new spring is reduced by 10 mm.

Measure the height of the old spring.

If the height of the old spring has decreased from 9 to 11 mm (± 10%) - it will still serve, if more - replace the old spring.

Checking valve clearance in the guide sleeve

There are two ways to check the clearance between the valve stem and the valve guide.

The first way

Ремонт головки блока цилиндров двигателя К4М

Lift the valve head by 25 mm, then measure the valve movement in the direction of the arrows (see Fig. 2.68) with an indicator at an angle of 90˚ to the camshaft axis.

Half of this will give the clearance between the stem and the valve guide.

Second way

Measure the diameter of the valve stem and the inside diameter of the guide bush (see figure 11).

Ремонт головки блока цилиндров двигателя К4М

Nominal clearance, mm:

- inlet valves 0.015-0.048;

- exhaust valves 0.029-0.062.

Checking the camshafts

Ремонт головки блока цилиндров двигателя К4М

The height of the cams H (see Fig. 12) of the camshafts must correspond to the data in the table.

Camshaft dimensions

Parameters mm

Axial clearance of camshafts

intake and exhaust valves 0.080-0.178

Diametral clearance in supports 0.040-0.082

Number of supports 6

Camshaft journal diameter (see Figure 14):

- neck number 1; 24,979-25,000

- neck number 2, 3, 4, 5; 24,979-25,000

- neck No. 6 27.979-28.061

Cam height H (fig. 12):

- intake valves 40.661 ± 0.030

- exhaust valves 40.038 ± 0.030

Otherwise, replace the camshaft or carry out refurbishment.

The main dimensions of the camshafts are shown in the table.

- Check the clearance of the camshaft journals in the bearings of the block head, for this;

- Reinstall the block head cover, tighten the bolts of its fastening to the specified tightening torque.

Ремонт головки блока цилиндров двигателя К4М

- Using a bore gauge, measure the diameters of all holes in the camshaft bearings (see Fig. 13), write down the measurement results.

Note. Measurements should be made in the vertical plane of maximum wear.

Ремонт головки блока цилиндров двигателя К4М

- Use a micrometer to measure the diameters of the camshaft bearing journals (see Fig. 14).

Measurements should be taken on each neck in two perpendicular planes. Take the smallest value on the neck for the baseline.

- Compare the measurement results with the limit values.

Then calculate the clearances for all necks and compare the obtained values ​​with the maximum permissible values. According to the results:

replace the camshaft, cylinder head, or both.

Note. If the camshaft and block head are worn out, remanufacturing (spraying with subsequent processing) is possible.

Often the price of such repairs is much cheaper than buying new parts.

- If previous checks did not show the need to replace parts, then check the axial clearance of the camshafts as described below, if necessary replace the worn parts.

If the parts are new, check it anyway, it is not difficult, but important to be sure of the results of the repair being carried out.

- Install the camshafts ensuring that they are in the correct position.

- Install the cylinder head cover.

Ремонт головки блока цилиндров двигателя К4М

- Tighten in the order shown in fig. 15, the required moment:

- cylinder head bolts 13, 20, 22, 23, Nm 8;

- bolts of the block head cover from 1 to 12, from 14 to 19 and from 21 to 24, Nm 12.

- Loosen the head cover bolts 13, 20, 22, 23.

- Tighten in the order shown the cylinder head cover bolts 13, 20, 22, 23 to 12 Nm.

Ремонт головки блока цилиндров двигателя К4М

Attach the magnetic support of the axial clearance tester Mot. 588 on the cylinder head using the retaining plate (3) tool Mot. 588, tighten it with the bolts (1) fastening the oil separator and spacers (2) with the following dimensions (see Fig. 16):

- outer diameter, mm - 18;

- bolt hole diameter, mm - 9;

- height, mm - 15.

- Check the axial clearance of the camshaft, which should be between 0.080-0.178 mm.

- Remove the cylinder head cover and camshafts.