Device
Pic. 2.140. Cylinder head and valve train
The cylinder head is cast aluminum alloy with pressed cast iron seats and valve guides. The upper part of the bushings is sealed with rubber-metal oil seals.
Guide bushes with larger outside diameters are available as spare parts.
In the upper part of the cylinder head, there are supports for the camshaft journals. The supports are detachable. The top half is in the bearing housings and the bottom half is in the cylinder head. The bearing holes are machined complete with bearing housings, so they are not interchangeable and the cylinder head can only be replaced complete with housings.
The valves are actuated by camshaft cams via hydraulic tappets. Adjustment of gaps in the valve drive mechanism with hydraulic tappets is carried out automatically during engine operation.
Disassembly
Pic. 2.141. The procedure for removing the cylinder head bolts
With a special tool (wrenches for cylinder head bolt 09221-32001, 09221-11000) unscrew the cylinder head bolts in the order shown in the figure (pic. 2.141).
Pic. 2.142. Removing crackers, spring plates, springs and valves using a special tool
With a special tool (valve spring compressor tool 09222-28000 and adapter 09222-28100) remove the crackers from the valve spring plate. Then remove the valve spring cap, valve spring, valve spring seat and valve (pic. 2.142).
Note. Keep the parts for each valve separately as a set to avoid confusion during installation.
Pic. 2.143. Removing oil seals
With a special tool (oil seal remover 09222-29000) remove oil seals (pic. 2.143).
Note. Valve stem seals must not be reused.
Checking the cylinder head
Check the cylinder head for cracks, damage and signs of coolant leakage. If cracks are found, replace the cylinder head.
Completely clean the cylinder head of scale, carbon deposits and remnants of the old sealant and gasket. After cleaning the oil passages, blow them out with compressed air to remove any blockage.
Pic. 2.144. Checking the flatness of the mating surface of the cylinder head
Check the flatness of the mating surface of the cylinder head in the directions shown in Fig. 2.144.
If the flatness exceeds the limit in either direction, either replace the cylinder head or lightly sand the mating surface of the cylinder head.
Non-flatness of the mating surface of the cylinder head:
- nominal value - less than 0.03 mm;
- the maximum allowable value is 0.06 mm.
Valve train parts
Pic. 2.145. Valve cleaning
Use a wire brush to thoroughly clean the valve (pic. 2.145).
Pic. 2.146. Valve check
Check each valve and valve stem for wear, damage, and poppet distortion (pic. 2.146).
Replace valve if necessary. If there are dents or significant wear on the end of the valve stem, remake the end of the valve stem. The thickness of the layer to be removed during mechanical processing of the end of the valve stem should be minimal. In addition, process the working chamfer of the valve seat.
Replace the valve if the valve disc thickness is less than the limit.
Valve disc thicknesses are shown below.
Rated value:
- intake valve - 1.15 mm;
- exhaust valve - 1.35 mm.
Maximum allowable value:
- intake valve - 0.80 mm;
- exhaust valve - 1.00 mm.
Valve springs
Pic. 2.147. Measuring the length of the valve spring in the free state
Check the free length of each valve spring. If the spring length is less than the limit, replace the valve spring (pic. 2.147).
Pic. 2.148. Checking the deviation of the spring axis
Using a square, check the deviation of the axis of each spring from perpendicular to the supporting surface (non-perpendicularity) (pic. 2.148).
If the misalignment is greater than the limit, replace the valve spring.
Valve spring
Nominal free spring length: 48.86 mm.
- Spring length under load 183 N: 39.00 mm.
- Spring length under load 400 N: 30.50 mm.
- Spring axis deflection (non-perpendicularity): 1.5°or less.
Maximum allowable value:
- Spring free length: 47.86 mm.
- Spring axis deflection (non-perpendicularity): 3°.
Valve guides
Pic. 2.149. Checking clearance between valve guide and valve stem
Check clearance between valve guide and valve stem (at several points along the length). If the clearance is greater than the limit, replace the valve guide (pic. 2.149).
The clearance values between the valve guide and the valve stem are given below.
Rated value:
- intake valve - 0.02–0.05 mm;
- exhaust valve - 0.035–0.065 mm.
Maximum allowable value:
- intake valve - 0.10 mm;
- exhaust valve - 0.13 mm.
Valve seat rebuild
Pic. 2.150. Valve seat repair diagram
Check the valve seat for signs of overheating and uneven contact with the valve face. If necessary, or restore (machine), or replace the valve seat. Check the valve guide for wear before rebuilding the valve seat. If the guide bushing is worn, replace it first and then rebuild the valve seat. Restoration of the valve seat is carried out with a special tool (cutters or on machine tools). The width of the contact surface of the valve seat must correspond to the nominal values and the contact patch must be located evenly in the center of the working chamfer of the valve disc. After restoring the seat, the valve and valve seat should be lapped using lapping paste.
Valve seat replacement
Machine (cut off) replaceable valve seat from the inside to reduce the thickness of its walls.
Pic. 2.151. Scheme of boring holes in the cylinder head
Bore a hole in the cylinder head to install a valve seat of the appropriate repair size (increased diameter) (pic. 2.151).
Heat the cylinder head to approximately 250°C and press a new oversize seat into the cylinder head bore.
Lappe the valve to the new seat using lapping paste.
The width of the contact surface of the valve seat for the inlet channel is 1.1-1.5 mm, for the outlet channel - 1.3-1.7 mm.
Valve Guide Replacement
Pic. 2.152. Pressing out the old valve guide
With a special tool (mandrel for installing the guide bushing 09221-22000А/В) press the old valve guide out of the cylinder head towards the gasket surface (pic. 2.152).
Ream the cylinder head bore to install the correct oversize valve guide (increased diameter).
Pic. 2.153. Difference between guide sleeve lengths for intake and exhaust valves
With a special tool (mandrel for installing the guide bushing 09221-22000А/В) Press in the new valve guide from the top surface of the cylinder head. Pay attention to the difference in the lengths of the guide bushings for the intake and exhaust valves (pic. 2.153).
Note. Do not install the valve guide if it does not match the oversize.
After installing the valve guide, insert the new valve and check that the clearance between the valve guide and the valve stem is correct.
After replacing the valve guide, check that the valve is properly seated in the seat. Rework the valve seat if necessary.
Assembly
Apply engine oil to all rubbing and rotating parts.
Install the valve spring seats.
Note. Thoroughly clean all parts before assembly.
Pic. 2.154. Installing the valve stem seal
With a special tool (mandrel for installing the valve stem seal 09222-22001) with a light blow, install the oil scraper cap in place (pic. 2.154).
Note. Reuse of valve stem seals is not allowed.
Note. Improper installation of the valve stem seal can result in oil leaks through the valve guide.
Lubricate the valve stem with engine oil. Insert the valve into the guide sleeve.
Do not apply force when passing the valve stem through the valve stem seal. After installing the valve, check the smoothness of its movement.
Pic. 2.155. Valve spring installation diagram
Install the valve spring so that the painted coil of the spring is located near the spring seat (up), and then install the valve spring cap (pic. 2.155).
Pic. 2.156. Installation of crackers
With a special tool (valve spring compressor tool 09222-28000 and adapter 09222-28100) compress the valve spring and install the crackers. Before removing the special tool after installing the valve, check that the nuts are securely installed (pic. 2.156).
Note. When compressing the valve spring, make sure that the spring plate does not touch the valve stem seal.
Clean the mating surfaces for the gasket on the head and cylinder block.
Check that the cylinder head gasket identification marks match the specifications.
Install the cylinder head gasket on the cylinder block with the identification mark facing up (to the cylinder head).
Pic. 2.157. The order of tightening the cylinder head bolts
Tighten bolts of fastening of a head of the block of cylinders the nominal moment in the order shown in drawing fig. 2.157.
Tightening torque for the cylinder head bolts:
- М10–25 Nm + (60–65°) + (60–65°);
- М12–30 Nm + (60–65°) + (60–65°).