Checking and bleeding hydraulic valve clearance compensators (Mitsubishi Space Star)

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 must be performed.

Notes

(1) Abnormal noise caused by a malfunction of the hydraulic valve clearance adjusters appears immediately after the engine is started and changes with the engine speed regardless of the engine load. If the abnormal noise does not appear immediately after the engine is started or does not change with the engine speed, the hydraulic valve clearance adjusters are not the source of the noise.

(2) If the hydraulic valve clearance compensator is faulty, the abnormal noise is rarely eliminated by warming up the engine at idle speed.

However, the abnormal noise may only disappear when the seizure is caused by contaminated engine oil that is not properly maintained.

1. Start the engine.

2. Make sure that the abnormal noise appears immediately after the engine is started and changes with the engine speed.

If the abnormal noise does not appear immediately after starting the engine or does not change with engine speed, the hydraulic valve clearance compensators are in good condition. 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 the N position to the D position 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 out (In this case, the hydraulic valve clearance compensators are in good condition).

4. After warming up the engine, let it idle to check for abnormal noise.

If the noise decreases or disappears, clean the hydraulic valve lash adjusters as they may be seized. If the abnormal noise level does not change, proceed to step 5.

5. Bleed the hydraulic valve clearance compensators.

6. If the abnormal noise does not disappear after bleeding, clean the hydraulic valve clearance adjusters.

Bleeding hydraulic tappets

Notes

(1) After the vehicle has been parked for a long time, engine oil may leak from the hydraulic valve clearance compensators, and when the engine is started, air will enter the high-pressure chamber of the compensators.

(2) After the vehicle has been parked for a long time, engine oil may drain from the oil supply passage and it will take some time before engine oil is supplied to the hydraulic valve clearance adjusters and air is forced out of the high pressure chambers of the adjusters.

(3) In any of these cases, the abnormal noise can be eliminated by bleeding the hydraulic valve clearance compensators.

1. Check the engine oil level and, if necessary, top it up to normal (Fig. 2.11).

Notes

(1) If the engine oil level is too low, air will escape through the oil filter and enter the oil supply channel to the hydraulic valve clearance compensators.

(2) If the engine oil level is too high, the engine oil may be foamed by the rotating crankshaft, causing more air to enter the oil.

(3) If the oil quality 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 clearance adjuster, the air is compressed when the valve opens, resulting in abnormal noise when the valves close (Fig. 2.12). This phenomenon is similar to the increased valve clearance. The hydraulic valve clearance adjuster recovers its functionality after all the air is removed from the high-pressure chamber of the adjuster.

2. Start the engine and warm it up for 1-3 minutes at idle speed.

3. Perform the cycles shown in Figure 2.13 with the engine running without load. Usually, the abnormal noise will disappear after repeating 10-30 cycles. However, if no change in noise is observed after 30 cycles, the noise may be caused by other engine faults.



4. After eliminating the abnormal noise, repeat the action shown in Figure 2.13 five more times.

5. To ensure that the abnormal noise has been eliminated, let the engine idle for 1-3 minutes.