REMOVAL & INSTALLATION
See Figures 1 and 2
The hydraulic lash adjusters are designed to keep the lash between the rocker arm and the valve at a constant rate, and also eliminate almost all periodical adjustment of the valve lash. The lash adjuster is a precision part, and it needs to be kept free from dust and other foreign matter. The lash adjusters do not need to be disassembled.
For the procedures on these engines refer to the camshaft removal and installation procedures, located in this section.
On Vehicle Inspection
See Figures 3 and 4
If a clanging noise due to the lash adjuster produced immediately after the engine has started or during operation persists, perform the following checks:
Check the engine oil, and add or replace if necessary.
- If the engine oil is low, the air drawn in from the oil strainer will be trapped in the oil passage.
- If the engine oil level is higher than the specified level, agitation of oil by the crankshaft could cause a large amount of air to enter the oil.
- A deteriorated oil contains a large amount of air, because the air, once trapped, is not readily separated from the oil.
If the air trapped due to these causes enters the high pressure chamber in the lash adjuster, the air in the high pressure chamber will be compressed while the valve is in the opened position. The lash adjuster will be drawn too far in, and will produce noise when the valve closes. This is the same phenomenon that occurs when the valve clearance is adjusted to an excessive dimension.
In this case, the normal condition will be restored if the air escapes from the lash adjuster.
Start the engine and slowly race (accelerate the engine from idling speed to 3,000 rpm in 30 seconds and then decelerate it to the idling speed in 30 seconds) it several times (less than 10 times). If racing the engine causes the noise to die away, it means that the air has escaped from the high pressure chamber of the lash adjuster and that the lash adjuster has regained its normal functions.
- When the vehicle is parked on a slope for a long period of time, the oil in the lash adjuster will decrease. When the engine is started, the air might enter the high pressure chamber.
- After a long period of parking during which the oil in the oil passage goes away, it will take some time before the oil is re-supplied to the lash adjuster. Therefore, the air could enter the high pressure chamber.
If any abnormal noise is not eliminated by racing, check the lash adjuster.
- Stop the engine.
- Set the engine so that cylinder No. 1 is positioned at the top dead center of the compression stroke.
- Press the rocker arm at the area indicated by the white arrow mark to check whether the rocker arm is lowered or not.
- Slowly turn the crankshaft 360° clockwise.
- In the same procedure as step "c", check the rocker arm at the area indicated by the black arrow mark.
- Push down the rocker arm at a portion located right above the lash adjuster. If the rocker arm goes down readily, the lash adjuster is defective. Replace it with a new one in accordance with Step 4. In addition, when replacing the lash adjuster, be sure to remove air positively from the lash adjuster before installation. Then perform inspection in accordance with steps "a" through "e" to make sure that there is no abnormality. In addition, if the rocker arm is felt to be very stiff or cannot be pushed down when it is pushed, the lash adjuster is in the normal condition. Therefore, check for other causes of noise.
Bleeding and Checking
When cleaning or checking the lash adjusters, use only clean diesel fuel. To test the lash adjusters, follow this procedure.
- Immerse the lash adjuster in clean diesel fuel.
- While lightly pushing down the inner steel ball using a small wire, move the plunger up and down four or five times to bleed air. The use of the retainer facilitates the air bleeding of the rocker arm mounted type lash adjuster.
- Remove the small wire and press the plunger in. If the plunger is hard to be pushed in, the lash adjuster is normal. If the plunger can be pushed in all the way readily, bleed the lash adjuster again and test again. If the plunger is still loose, replace the lash adjuster.
Upon completion of bleeding the air out of the lash adjuster, hold the adjuster upright to avoid the diesel fuel from spilling.
- After air bleeding, set the lash adjuster on the special tool (leak down tester MD998440).
- After the plunger has gone down somewhat 0.008-0.020 in. (0.2-0.5mm), measure the time needed for it to go down an additional 0.04 in. (1mm). Replace if the measured time is not between 4-20 seconds.