Identification of knocks and noises
It is not necessary to pinpoint exactly which part in the engine is responsible for the knock, your circuit is simply to determine if there are any major engine parts that may be causing the noise you are hearing. If the knocking part refers to the main parts of the engine, then it does not matter which particular part, the repair in all cases is the same engine bulkhead.
Car enthusiasts use three tools to find a possible source of knocking in a car: high-voltage wires, a stethoscope, and a rubber hose.
High voltage spark plug wires
With the engine idling, disconnect and then reconnect each high voltage wire in turn. If the intensity of the knocking changes when one of the high-voltage wires of the spark plugs is disconnected, then the knocking comes from the connecting rod bearing. If the sound doesn't change much, then it's probably the result of a main bearing failure or something else. Don't forget about such a thing as valve adjustment.
Stethoscope
The mechanic's stethoscope has the ability to detect engine noises. Place the end of the stethoscope on the cylinder block or cylinder head where the suspect part is. When a sound is detected with the stethoscope, move the end of the stethoscope around the area until the sound is at its loudest. The part closest to where the sound is most intense is likely to have a problem. Keep in mind, however, that sound can be transmitted from one place to another through metal.
Rubber hose
If you don't have a stethoscope, use a piece of rubber tubing. It doesn't work as well as a stethoscope, but it still works.
Smoke analysis
Engine diagnostics use the three visible colors of smoke black, white and blue.
Black
Black or dark brown smoke is usually associated with an engine running too rich. Although engine condition can be affected by the air/fuel ratio, especially on fuel injected engines, engine repair is the last resort to reduce smoke. Refer to the injection system repair information for more details.
White
White smoke has two common causes: transmission fluid and antifreeze (coolant). If the car is equipped with an automatic transmission, then pay attention to the vacuum modulator. The vacuum modulator is usually located at the rear of the gearbox (checkpoint) next to the output shaft housing. It is easy to identify as the vacuum hose goes into it. Remove the vacuum hose and check for transmission fluid in the hose. If you find transmission fluid in the hose, replace the vacuum modulator, this is the most likely source of white smoke.
If you can't find transmission fluid in the vacuum hose, or the vehicle is not equipped with an automatic transmission or does not have a vacuum modulator, then the most likely source of white smoke is a damaged cylinder head gasket, a crack in the cylinder head, or the cylinder block itself. These faults can be confirmed with compression test, or better still, cylinder leak test. See below for details on using a cylinder leak detector.
It's pretty easy to tell if white smoke is from transmission fluid or coolant. The coolant has a sweet smell and the transmission fluid has a smoky smell.
Blue
Blue smoke indicates engine oil burning. Pay attention when smoke comes out of the exhaust pipe. If smoke appears during acceleration, then worn piston rings are its source. If it appears during engine braking, then pay attention to the valve guides.
PCV System Check (exhaust gas recirculation)
Crankcase pressure can affect whether or not the intake manifold vacuum will draw engine oil into the intake manifold. Check the PCV system before deciding to repair an engine due to a smoking problem.
You can choose one of two possible ways to check the PCV system. One way is to replace the PCV valve and check the vent hose for blockage. A more thoughtful approach is to purchase a special PCV tester from the auto shop that fits over the PCV vent hose to determine if the crankcase pressure is within the correct limits. Of course, if the pressure isn't right then you need to replace the PCV valve and check the vent hose for blockage.
Checking with a vacuum gauge
The vacuum gauge is a convenient device for diagnosing malfunctions of the gas distribution mechanism and camshaft. Any of these faults will cause manifold pressure pulsation (this can be seen by the jumps of the arrow of the device). However, manifold pressure pulsation can be caused by faulty ignition systems or faulty pistons. The vacuum gauge should only be used to confirm the presence of a fault, not to indicate that fault.
Using a vacuum gauge is an easy way to start separating low compression problems as a result of piston ring or head gasket failures, or as a result of valve failures. With the engine idling, connect a vacuum gauge to the intake manifold. If the gauge pointer jumps back and forth a lot, then some valves are not providing the correct seal. Low compression due to faulty piston rings or cylinder head gasket also results in needle jumps but not as sharp.
Differences between the possible causes of low compression determined with a vacuum gauge require a lot of experimentation and are highly subjective. Two other methods are a compression test and a cylinder leak test.
Cylinder Leak Check
The cylinder leak test is a higher level test than the compression test, although its purpose is the same. It requires more equipment. When the piston is at TDC on the compression stroke, connect the tester (device) to check for leaks in the cylinders to the first cylinder. Measure the leakage percentage. Additionally, use a piece of rubber hose with one end to your ear to determine where the leak is. Insert the other end of the hose into the open hole in the fuel injection throttle body. If a lot of air comes out of there, then you have a damaged intake valve. If a hiss is heard from the exhaust pipe, the exhaust valve is damaged. Look at the coolant in the radiator. If there are a lot of bubbles in it, then you have a damaged cylinder head gasket, a crack in the head or in the block itself.