Examination
If a characteristic abnormal noise appears after starting the engine and does not disappear after the engine warms up, the hydraulic valve clearance compensators may be faulty and the following check should be performed.
Notes
(1) Abnormal noise caused by a malfunction of the hydraulic valve clearance compensators appears immediately after the engine is started and changes with the engine speed, regardless of its load. If the abnormal noise does not appear immediately after starting the engine or does not change with engine speed, then the hydraulic valve clearance compensators are not the source of the noise.
(2) If the hydraulic valve clearance compensator is faulty, the abnormal noise rarely goes away when the engine warms up at idle.
However, the abnormal noise may only disappear when the seizure is caused by engine oil contamination that is not properly maintained.
1. Start the engine.
2. Verify that the abnormal noise appears immediately after starting the engine and changes with the change in engine speed.
If the abnormal noise does not appear immediately after starting the engine or does not change with engine speed, then the hydraulic valve clearance compensators are working. Check the engine for other sources of noise. If the abnormal noise does not change with engine speed, it is likely caused by a malfunction of other engine components.
3. With the engine idling, move the selector lever from position N to position D, and check that there is no change in the abnormal noise level.
If the abnormal noise level changes, the main or connecting rod bearing shells may be worn (In this case, the hydraulic valve clearance compensators are in good working order).
4. After warming up the engine to check for abnormal noise, leave it to idle.
If the noise decreases or disappears, clean the hydraulic valve clearance adjusters as they may be stuck. If the abnormal noise level has not changed, go to step 5.
5. Bleed the hydraulic valve lash adjusters.
6. If abnormal noise does not disappear after bleeding, clean the hydraulic valve clearance compensators.
Bleeding hydraulic pushers
Notes
(1) After the vehicle has been parked for a long time, engine oil may leak from the hydraulic valve clearance compensators, and air will enter the compensator high pressure chamber when the engine is started.
(2) After the vehicle has been parked for a long time, engine oil may drain from the oil supply port and it will take some time before engine oil is supplied to the hydraulic valve clearance compensators and air is forced out of the compensator pressure chambers.
(3) In any of these cases, the abnormal noise can be eliminated by venting the hydraulic valve lash adjusters.
1. Check the engine oil level and top up if necessary (pic. 2.11).
Pic. 2.11. The location of the marks on the dipstick for measuring the level of engine oil.
Notes
(1) If the engine oil level is too low, air escapes through the oil filter and enters the lubrication passage to the hydraulic valve clearance adjusters.
(2) If the engine oil level is too high, the engine oil can foam up from the rotating crankshaft, causing more air to enter the oil.
(3) If the quality of the oil deteriorates due to mixing with air, the air will be difficult to separate from the engine oil and its content in the oil will increase.
(4) If air mixed with engine oil is supplied to the high pressure chamber of the hydraulic valve gap adjuster, the air is compressed when the valve is opened, resulting in abnormal noise when the valves are closed (pic. 2.12). This phenomenon is analogous to increased valve clearance. The hydraulic valve clearance compensator recovers its performance after removing all air from the compensator high pressure chamber.
Fig. 2.12 Location of the high pressure chamber of the hydraulic valve gap compensator.
2. Start the engine and warm it up for 1-3 minutes while idling.
3. Carry out the cycles shown in Figure 2.13 with the engine running without load. Usually the abnormal noise is eliminated after repeating 10-30 cycles. However, if no change in noise is observed after 30 cycles, the noise may be caused by other engine problems.
4. After eliminating the abnormal noise, repeat the action shown in Figure 2.13 five more times.
5. To make sure that the abnormal noise is eliminated, let the engine idle for 1-3 minutes.
Pic. 2.13. Cycles of changing engine operating modes when pumping hydraulic valve clearance compensators