Checking Abnormal Noise

If an abnormal noise (rattling noise) probably caused by the lash adjusters is heard, and the noise does not stop, check as follows:
1. Check the engine oil, and if required, refill or change it.

NOTE:
- If the amount of the engine oil is insufficient, air will be sucked in from the oil strainer and mix in the oil passage.
- If the amount of the engine oil is more than the specified amount, it will be stirred by the crankshaft to make a lot of air mix in with the oil.
- If the oil is deteriorated, it will not easily separate from air and the amount of air mixed in the oil will increase.





- If the air which has mixed in the oil due to the above causes enters the high-pressure chamber in the lash adjusters, the air in the high-pressure chamber will be pressurized during opening of the valve, which causes the lash adjusters to shrink excessively, and an abnormal noise will be generated when the valve is closed. This is the same phenomenon as the one when the valve clearance has been excessively adjusted by mistake. In this case, if the air which has entered the lash adjusters is bled, things will be normalized.

2. Start the engine and perform gentle racing several times (less than 10 times). If the abnormal noise stops by racing, the air is bled from the high pressure chamber of the lash adjusters and the function of the lash adjusters is normalized. After raising the engine speed from idling to 3,000 RPM (gradually in 30 seconds), drop the speed gradually (in 30 seconds) to idling.

NOTE:
- If the vehicle is parked on a slope for long, the oil in the lash adjusters will be decreased and air may enter the high-pressure chamber when the vehicle is started.
- After the vehicle is parked for long, air may enter the high-pressure chamber because the oil in the oil passage will be gone and it will take a time before the oil is supplied to the lash adjusters.

3. If an abnormal noise does not stop by racing the engine, check the lash adjusters according to the following procedures:
(1) Stop the engine.
(2) Set the No. 1 cylinder of the engine to the compression top dead center.





(3) Push the rocker arm indicated by the white arrow mark as shown in the illustration and check whether or not the arm lock goes down.
(4) Turn slowly the crankshaft 360° clockwise.
(5) Check the rocker arm indicated by the black arrow mark as shown in the illustration.





(6) If the rocker arm can be lowered easily when the part of the rocker arm which is directly above the top of the lash adjuster is pressed, the lash adjuster is defective and should be replaced with a new part. Furthermore, when replacing the lash adjuster, bleed all of the air from the lash adjuster and then install. After this, check that there is no problem by checking in steps (1) to (5).

NOTE: A leak-down test can be carried out to accurately determine whether the lash adjuster is defective or not. Furthermore, if the rocker arm feels extremely stiff and cannot be lowered when it is pressed, the lash adjuster is normal, so investigate for some other cause of the abnormality.