4G15 / 4G63 / Mitsubishi - Lash Adjuster Check & Air Bleeding

Previous Clean Job - Diesel Cleaning & Bleeding Tappets/Lash Adjusters/Hydraulic lifters - MD171130 MD376687 - 4G15, 4G63 etc
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LASH ADJUSTER CHECK

If an abnormal noise (knocking) that seems to be coming from the lash adjuster is heard after starting the engine and dose not stop, carry out the following
check.
NOTE: .
• If the vehicle is parked on a slope fir a long period of time, the amount of oil inside the lash adjuster will decrease, and air may get into the high pres-sure chamber when starting the engine.
• After parking the vehicle for long periods, the oil drains out of the oil passage, and it takes time for the oil to be supplied to the lash adjuster, so air can get into the high-pressure chamber.
• If either of the above situations occur, the abnor-mal noise can be eliminated by bleeding the air from inside the lash adjusters.
• The abnormal noise which is caused by a prob-lem with the lash adjusters is generated after the engine is started, and will vary according to the engine speed. However, this noise is not related to the actual engine load.
Because of this, if the noise dose not occur immedi-ately after the engine is started, if it dose not change in accordance with the engine speed, or if it changes in accordance with the engine load, the source of the noise is not the lash adjusters.
• If there is a problem with the lash adjusters, the noise will almost never disappear, even if the engine has been run at idle to let it warm up. The only case where the noise might disappear is if the oil in the engine has not been looked after properly and oil sludge has caused the lash adjusters to stick.

1. Start the engine.
2. Check that the noise occurs immediately after the engine is started, and that the noise changes in accordance with changes in the engine speed.
If the noise dose not occur immediately after the engine is started, or if it dose not change in accordance with the engine speed, the problem is not being caused by the lash adjusters, so check for some other cause of the problem. Moreover, if the noise dose not change in accordance with the engine speed, the cause of the problem is probably not with the engine (In these cases, the lash adjusters are normal).
3. While the engine is idling, check that the noise level does not change when the engine load is varied (for example, by shifting from N to D).If the noise level changes, the cause of the noise is probably parts striking because of worn crankshaft bearings or connecting rod bearings (In such cases, the lash adjusters are normal).
4. After the engine has warmed up, run it at idle and check if any noise can be heard. If the noise has become smaller or disappeared, oil sludge could make the lash adjusters stick. Clean the lash adjusters (Refer to GROUP 11D − Rocker Arms and Camshaft − Rocker Arms and Camshaft Inspection P.11D-30). If not improved, go to step 5.
5. Bleed air from the lash adjusters (Refer to P.11C-16).
6. If the noise has not disappeared even after the air bleeding, clean the lash adjusters (Refer to GROUP 11D − Rocker Arms and Camshaft − Rocker Arms and Camshaft Inspection P.11D-30).

Air Bleeding
1. Check the engine oil and replenish or replace the oil if necessary.
NOTE: .
• If there is an only small amount of oil, air will be drawn in through the oil screen and will get into the oil passage.
• If the amount of oil is greater than normal, then the oil will being mixed by the crankshaft and a large amount of air may get mixed into the oil.
• If the oil is degenerated, air and oil will not separate easily in oil, and the amount of air mixed into the oil will increase.
If the air which has been mixed in with the oil due to any of the above reasons gets into the high pressure chamber of the lash adjuster, the air inside the high pressure chamber will be compressed when the valve is open and the lash adjuster will over-compress, resulting in abnormal noise when the valve close. This is the same effect as if the valve clearance is adjusted to be too large by mistake. If the air inside the lash adjusters is then released, the operation of the lash adjusters will return to normal.




2. Run the engine at idle for 1 − 3 minutes to let it warm up.
3. With no load on the engine, repeat the drive pattern shown in the illustration above and check if the abnormal noise disappears (The noise should normally disappear after 10 − 30 repetitions, but if there is no change in the noise level after 30 repetitions or more, the problem is probably not due to air inside the lash adjusters).






















4. After the noise has disappeared, repeat the drive pattern shown in the illustration above a further 5times.
5. Run the engine at idle for 1 − 3 minutes and check that the noise has disappeared.