ENGINE DIAGNOSIS
| SYMPTOMS | PROBABLE CAUSE | REMEDY |
|---|---|---|
| Compression is too low | Blown cylinder head gasket | Replace the gasket. |
| Worn or damaged piston rings | Replace the rings. | |
| Worn piston or cylinder | Repair or replace the piston and/or the cylinder block. | |
| Worn or damaged valve seat | Repair or replace the valve and/or the seat ring | |
| Drop in engine oil pressure | Engine oil level is too low | Check the engine oil level. |
| Malfunction of engine oil pressure switch | Replace the engine oil pressure switch. | |
| Clogged oil filter | Install a new filter. | |
| Worn oil pump gears or cover | Replace the gears and/or the cover. | |
| Thin or diluted engine oil | Change the engine oil to the correct viscosity. | |
| Stuck (opened) oil relief valve | Repair the relief valve. | |
| Excessive bearing clearance | Replace the bearings. | |
| Engine oil pressure too high | Stuck (closed) oil relief valve | Repair the relief valve. |
| Noisy valves | Incorrect valve clearance < Intake side > | Adjust valve clearance |
| Malfunction of lash adjuster (including entry of air into high pressure chamber) < Exhaust side > | Check the lash adjuster. | |
| Thin or diluted engine oil (low engine oil pressure) | Change the engine oil. | |
| Worn or damaged valve stem or valve guide | Replace the valve and/or the guide. | |
| Connecting rod noise/main bearing noise | Insufficient oil supply | Check the engine oil level. |
| Thin or diluted engine oil | Change the engine oil. | |
| Excessive bearing clearance | Replace the bearings. |
ENGINE DIAGNOSIS
WHEN USING SCAN TOOL MB991958
Required Special Tools
- MB991668: Belt Tension Meter Set
- MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: Vehicle Communication Interface (V.C.I.) MB991910: MUT-III Main Harness A
| CAUTION | To prevent damage to scan tool MB991824, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991824. |
Scheme 156
Scheme 157
- Connect special tool MB991668 to scan tool MB991824.
- Connect scan tool MB991910 to scan tool MB991824.
- Connect scan tool MB991910 to the data link connector.
- Turn the ignition switch to the "ON" position and select "Belt Tension" from the menu scan tool MB991824 screen. CAUTION: The temperature of the surface of the belt should be as close as possible to underhood temperature. Do not let any contaminants such as water or oil get onto the microphone. If strong gusts of wind blow against the microphone or if there are any loud sources of noise nearby, the values measured by the microphone may not correspond to actual values. If the microphone is touching the belt while the measurement is being made, the values measured by the microphone may not correspond to actual values. Do not take the measurement while the vehicle's engine is running.
- Hold special tool MB991668 (microphone) to the middle of the drive belt between the pulleys (at the place indicated by the arrow), about 10-20 mm (0.4-0.8 inch) away from the rear surface of the belt and so that it is perpendicular to the belt (within an angle of +/- 15 degree angle).
- Gently tap the middle of the belt between the pulleys (the place indicated by the arrow) with your finger as shown in the illustration, and check that the vibration frequency of the belt is within the standard value. Standard value: 143-169 Hz NOTE: Because the frequency depends on the belt material, confirm Part No. shown on the reverse of the belt.
Required Special Tools
- MB991668: Belt Tension Meter Set
- MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: Vehicle Communication Interface (V.C.I.) MB991910: MUT-III Main Harness A
Gently tap the middle of the belt between the pulleys (the location indicated by the arrow) with your finger as shown in the illustration, and check that the vibration frequency of the belt is within the standard value.
Note. Refer to for details on the method of measuring the vibration frequency using the scan tool.
Standard value
| ITEM | WHEN CHECKED | DURING ADJUSTMENT | DURING REPLACEMENT |
|---|---|---|---|
| Vibration frequency Hz | 124-160 | 134-151 | 160-189 |
STANDARD VALUE
Scheme 158
INSPECTION
- Check the oil pan for cracks.
- Check the oil pan sealant-coated surface for damage and deformation.
- Check the oil screen for cracked, clogged or damaged wire net and pipe.
Scheme 159
Required Special Tool
- MD998717: Crankshaft Front Oil Seal Installer
Scheme 160
- Apply a small amount of engine oil to the oil seal lip and then insert the o-ring.
- Using special tool MD998717, tap the oil seal into the front case.