Camshafts are replaced in the following cases: – pressure drop in the engine lubrication system
The cause of this malfunction is often increased wear of the camshaft journals and seats in the camshaft bearing housings.
When the sockets are worn out, the cylinder head assembly is replaced, since the sockets are processed together with the bearing housing installed on the head; – knocking of valves with serviceable hydraulic pushers (see “Checking and replacing hydraulic pushers”) in the valve mechanism.
This happens due to wear on the camshaft cams due to the use of low-quality engine oil or damage to the oil filter.
Remove the camshafts from the engine (see “How to replace the valve stem seals of a VAZ-21126 engine”).
Inspect the camshafts.
On the working surfaces of the journals 2, scuffs, nicks, scratches, and enveloping of aluminum from the bearing seats in the housings and the block head are not allowed.
On the working surfaces of cams 1, scuffing and wear in excess of 0.5 mm, as well as cut-shaped wear on the cams, are not allowed.
Replace the shaft with detected defects.
In workshops equipped with special devices and tools, you can check the radial runout of the camshaft journals (it should not exceed 0.02 mm).
Measure the diameters of the shaft support journals. They should be 23.915–23.931 mm.
Inspect the bearing housing...
Inspect the camshaft supports in the cylinder head.
Cracks on the body are not allowed.
No risks, scratches, scuffs, or excessive wear are allowed on the working surfaces of the journal supports.
Install the camshaft bearing housing on the cylinder head and tighten its mounting bolts to the recommended torque.
Measure the inner diameters of the camshaft housing supports.
They should be 24,000–24,025 mm.
Calculate the gaps between the shaft journals and the supports using the difference in size.
For new parts, the gaps should be 0.069–0.11 mm.
If after use the gaps exceed 0.2 mm, replace the camshafts.
If, even after replacing the shafts, the clearances exceed the maximum permissible value, replace the cylinder head assembly with the camshaft bearing housing.
Install the camshafts and all removed parts in the reverse order of removal.
Apply Loctite-574 type sealant in the form of a bead with a diameter of 2 mm to the surface of the cylinder head mating with the camshaft bearing housing.