Usually we begin to inspect and replace the hydraulic lifters when increased noise occurs during engine operation. As a rule, this is a ringing sound in the upper part of the engine.
Faults of the hydraulic lifters and methods for their correction are given in the table at the end of the article.
The hydraulic lifters of the VAZ-2112 engine, made in the form of cylindrical lifters located between the camshaft and the valves, combine two functions: transmitting force from the camshaft to the valves and eliminating clearances in their drive.
The operation of the hydraulic lifter is based on the principle of incompressibility of the engine oil, which constantly fills the internal cavity of the hydraulic lifter during engine operation and moves its plunger when a clearance appears in the valve drive. This ensures constant contact of the lifter with the camshaft lobe without clearance. Thanks to this, there is no need to adjust the valves during maintenance.
The operating principle of the hydraulic lifter is shown in Figure 1. Oil at the pressure required for the hydraulic lifter to operate is supplied to the internal cavities (А) and (Б) from passage В of the engine lubrication system through a side hole in the lifter 6, made in an annular groove on its cylindrical surface.
With the valve 1 closed, the lifter 6 (through the plunger 7) and the sleeve 9 are pressed by the expanding force of the spring 8 respectively against the camshaft lobe 5 and the end of the valve stem. The pressure in cavities (А) and (Б) is the same, the check valve 3 of the hydraulic lifter is pressed against its seat in the plunger 7 by the spring 2 — there are no clearances in the valve mechanism.
As the camshaft rotates, the lobe 5 runs onto the lifter 6, moving it and the plunger 7 connected to it. Movement of the plunger 7 in the sleeve 9 causes a sharp increase in pressure in cavity (Б). Despite small oil leaks through the clearance between the plunger and the sleeve, the lifter 6 and the sleeve 9 move as a single unit and open the valve 1.
As the camshaft continues to rotate, the lobe 5 reduces the pressure on the lifter 6, and the oil pressure in cavity (Б) becomes lower than in cavity (А). The check valve 3 opens and lets oil from cavity (А), connected to the engine oil line, into cavity (Б). The pressure in cavity (Б) increases, and the sleeve 9 and plunger 7, moving relative to each other, take up the clearance in the valve mechanism.
The pressure of the oil supplied to the hydraulic lifters is regulated by a valve installed in the cylinder head.
Since after the engine is stopped the oil from the passages coming from the oil pump drains into the oil sump, while the oil supply passages to the hydraulic lifters remain filled, air locks may form in the cavities of the latter after the engine is started. To eliminate them, calibrated compensation holes are provided in the engine oil supply passages, ensuring automatic purging of the hydraulic lifter cavities.
In addition, the compensation holes allow somewhat reducing the pressure of the oil entering the hydraulic lifters at high crankshaft speeds, when the pressure in the hydraulic lifter cavity may become so high that its lifter, resting on the back of the camshaft lobe, slightly opens the valve at a moment not corresponding to the valve timing phase.
Almost all faults of the hydraulic lifters are diagnosed by the characteristic noise produced by the valve train in various engine operating modes.
Sometimes valve noise can be eliminated by slightly turning the spring or the valve around its longitudinal axis. To do this, proceed as follows:
- Turn the crankshaft to the position in which the noisy valve begins to open slightly.
- Turn the spring slightly — the valve will turn at the same time.
- Start the engine. If the noise does not disappear, repeat operations 1 and 2.
If turning the spring and valve does not give the desired result, check the condition of the spring and measure the clearances between the valve stems and the guide bushings. Eliminate the increased (compared to nominal) clearances.
If the valve and spring are in good condition, but valve knocking is still heard during engine operation, the hydraulic lifter is faulty. Replace it as follows.
Replacing the hydraulic lifters
- Remove the receiver.
- Close the openings of the intake manifold with covers so that foreign objects do not get into it.
- Remove the ignition module.
- Disconnect the crankcase ventilation hose from the cylinder head cover pipe.
- Using a 10 mm wrench, loosen the bolt securing the bracket of the injector wiring harness connector.
- Using an 8 mm socket, loosen the 15 bolts securing the cylinder head cover (valve cover).
- Remove the cylinder head cover.
- Check the hydraulic lifter by pressing on it with a soft metal drift or a screwdriver (the camshaft lobe must be facing the lifter with its “back”). In normal condition, the hydraulic lifter should compress with considerable force. If the force is small, the hydraulic lifter must be replaced.
- To do this, remove the camshaft timing sprockets (see information on removing the sprockets).
- Disconnect the wire from the oil pressure warning lamp sensor.
- Using an 8 mm socket, loosen the 20 bolts securing the camshaft bearing housing.
- Using a 15 mm socket, loosen the three nuts securing the rear support bracket.
- Remove the rear support bracket.
- Remove the camshaft bearing housing.
- Take the spark plug guide tubes out of the housing.
- To distinguish the intake camshaft from the exhaust one: on the intake camshaft, near the first journal, there is a band.
- Take out the camshafts together with the oil seals.
- Remove the two rear plugs of the cylinder head and the camshaft bearing housing.
- By applying a magnet to the end face of the hydraulic lifter, take it out of its seat in the cylinder head.
- If necessary, replace the hydraulic lifter with a new one and install it in the seat.
Assembly
- Before assembly, clean the cylinder head and the camshaft bearing housing from remnants of old sealant and oil.
- Lubricate the support journals and cams of the camshafts with engine oil and lay the shafts in the supports of the cylinder head.
- On the surface of the shaft bearing housing that mates with the cylinder head, apply Loctite No. 574 sealant in a bead about 2 mm thick.
- Install the bearing housing and evenly tighten the fastening bolts.
- After lubricating the O-rings of the guide tubes with engine oil, install the tubes in the openings of the cylinder head and the bearing housing.
- Press in new camshaft oil seals.
- On the other side of the cylinder head, press in the plugs.
- Perform further assembly in the reverse order of disassembly.
- Before installing the cylinder head cover, apply Loctite No. 574 sealant to its surface mating with the bearing housing.
After replacing the hydraulic lifters, the engine may run with increased noise for a short time.
Possible faults of the hydraulic lifters, their causes and remedies
| Fault | Cause | Remedy |
|---|---|---|
| Increased noise immediately after starting the engine | Oil leakage from some of the hydraulic lifters during long parking. | Noise that disappears a few seconds after starting the engine is not a sign of a fault, since oil has leaked from some of the hydraulic lifters that were under the load of the valve springs of open valves (the oil supply passages remained open), and this lack is replenished at the beginning of engine operation. |
| *If the noise does not disappear for a long time — see other faults. | ||
| Intermittent noise at idle, disappearing when the crankshaft speed increases | Damage or wear of the check valve ball | Replace the hydraulic lifter |
| Contamination of the hydraulic lifter mechanism with wear products due to untimely oil changes or low oil quality | Clean the parts of the mechanism from contamination. Use the oil recommended in the operating manual | |
| Increased noise at idle of a warm engine, disappearing at increased crankshaft speed and completely absent on a cold engine | Oil flowing through the clearances between the plunger and the sleeve of the hydraulic lifter, increased due to wear | Replace the worn hydraulic lifter as a complete unit |
| Increased noise occurring at high crankshaft speed and disappearing at low speed | Foaming due to excess oil (above the upper mark on the dipstick) in the oil sump because of its churning by the crankshaft. The ingress of air-oil foam mixture into the hydraulic lifters disrupts their operation | Bring the oil level in the oil sump to normal |
| Air being drawn in by the oil pump when the oil level in the oil sump is excessively low | Bring the oil level in the oil sump to normal | |
| Damage to the oil pick-up due to deformation of the oil sump when hitting a road obstacle | Repair or replace the defective parts | |
| Constant noise of one or more valves, independent of crankshaft speed | Appearance of clearance between the lifter and the camshaft lobe due to damage or contamination of the hydraulic lifter parts | Remove the cylinder head cover, successively set the camshaft lobes with their projections upward and check for clearance between the lifters and the lobes. While pressing in (for example, with a wooden wedge) the hydraulic lifter being checked, compare the speed of its movement with the others. If there is clearance or increased movement speed, disassemble the hydraulic lifter and clean its parts from contamination or replace the hydraulic lifter |
*The following causes of increased noise at idle are possible, intensifying as the crankshaft speed increases to 1500 min-1 and not related to the operation of the hydraulic lifters:
- increased clearances between the valve stems and the guide bushings;
- misalignment of the valve and seat increased to a value exceeding the permissible one;
- non-parallelism of the ends of the valve springs;
- runout of the valve head chamfer greater than the permissible one.
