Please do the following:
- inspect the engine from above and below;
- minor oil leaks should not cause concern;
- the appearance of oil stains under the car while it is parked is a sign of a leak in the seals;
- periodically clean the engine with an engine cleaner;
- take a test drive of a few kilometers and check where the oil is leaking.
Possible leak locations
Places where oil may leak:
- sealing of crankshaft and camshaft;
- seals in the cylinder head cover;
- cylinder head gasket;
- oil pressure switch;
- oil filter seal;
- oil pan seal;
- rear crankshaft oil seal (at the engine/gearbox housing junction).
Bearing damage
The appearance of knocks in the engine compartment, which intensify as the oil heats up, is a consequence of bearing damage. The reasons for this may be:
- water in engine oil as a result of a damaged cylinder head gasket;
- insufficient lubrication due to too low oil level;
- too high revs on a cold engine (high oil viscosity).
Most often, connecting rod bearings fail, less often - crankshaft main bearings. When a bearing fails, serious engine repairs are required. But if you identify a damaged connecting rod bearing in time, when the crankshaft journal has not yet been damaged, then it is enough to replace its liners.
Determining a failed bearing
During this operation, all cylinders are switched off in turn for a short time.
Warning: Observe safety precautions when working with electronic ignition systems that contain high voltage. Also, do not run the engine with the spark plug caps removed to avoid damage to the control unit.
The following must be done:
- turn off the ignition;
- remove one spark plug tip. Instead of a spark plug, insert a nail, screwdriver or spare spark plug into the free tip. Firmly press this auxiliary structure to the "ground", it is best to clamp it through the emergency starter connection cable to the auxiliary battery;
- ask an assistant to start the engine and bring it to high speed;
- if the knocking becomes weaker when the tip is removed, then this cylinder has a faulty bearing;
- turn off the ignition, put on the spark plug tip and check the next cylinder in the same way.
If it is not possible to tow the car, you can drive with a damaged bearing at very low revs to a service station or to a parking place:
- turn off the ignition;
- disconnect the cylinder corresponding to the damaged bearing;
- remove the spark plug;
- as a result, the load on the bearing through the piston under pressure will decrease;
- to avoid damage to the control unit, the high-voltage wire from the faulty cylinder must be connected to ground:
- remove the tip from the wire;
- firmly connect the bare end of the cable to the "ground". The high-voltage wire should not hang freely in the air when the engine is running;
- you will no longer be able to reach your usual speed on the remaining cylinders. The engine should operate at a maximum of medium rotation speeds.
Note: When the engine is running and the spark plug is removed, air is sucked in and forced out again through the spark plug hole by the piston, causing a whistling noise. This should not be annoying.
Replacing connecting rod bearings
For this repair you will need connecting rod bearings - nominal size or oversize if the engine has already been overhauled once.
Engine running-in
During the first 1,000 km, engine parts (pistons and cylinders; bearings and shafts) must be run in. During this time, do not subject the engine to high loads:
- don't give it "full throttle"; with an automatic transmission, avoid the position of maximum and sharp pressing of the accelerator pedal.
- set medium speed only when the engine is warm; when the engine is cold, shift gears earlier;
- when the mileage reaches 1000–1500 km, gradually bring the car to maximum speed and the engine to maximum permissible speed.
Nominal and maximum speed
The combustion engine produces maximum power at its nominal speed. Attempts to exceed this speed do not increase power. High speeds provide an advantage only when overtaking.