Engine Ran Out of Oil Now Knocking

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    if my car ran low on oil and now there is a knocking sound what may be the cause


    If your car runs out of oil and on restoring the oil level it knocks, then it is likely you have done some major damage internally to the powerplant.

    Let’s face it, aside from other major liquids in an engine, oil plays what is perhaps the most important role in motoring. First, as you can guess, oil lubricates the engine. It enables the metal-on-metal contact that various parts such as gears and the drivetrain to handle the constant exposure to other metal parts without breaking down.

    If the oil is allow to go too low, engine parts lose their protection and become worn out almost immediately. In fact, if you let the oil go too low, then when the episode ends all you will have is the shell of car with no engine. Replacing that engine and getting it to work properly costs you the better part of $4,000, including labor, most of the time.

    You can see then that oil plays an important part as the engine’s primary lubricant. It also plays another part as a coolant. You see, engine oil has a major, but secondary job, it carries off lots of the heat generated by your engine.

    In order to do this, the gallery system of your car is of key importance. Not only does the series of conduits within the engine act to move oil around the engine, as it moves, it picks up the heat and carries it to the outer extremities of the engine. At that time, the engine oil passes its heat to the water jacket where it is then carried to the radiator and then on out of the engine. At the same time, the oil is cooled and it is then moved around the engine again where it is heated up and cooled down again.

    If the engine were left to just use the radiator and antifreeze/coolant to handle the cooling chores within your engine, then it is likely the system could only handle percentage of the car’s cooling requirements. Yes, the coolant does handle major cooling, but it is cooling and engine that already been cooled by the oiling system, in the first place.

    Now, as to the knocking that you have been left with, it is quite likely that when the oil went below acceptable limits and your engine overheated that something burned or went out of spec. For example, if the engine oil dips below the minimum levels needed by the driveshaft or half-shafts, it is quite possible that the bearings on the shaft were harmed. If the oil is too low, bearings can quickly go out of round and instead of orbiting in a circular manner they become eccentric ever so slightly that the do work but the also slap the side of their carriers as well. Thus you have the engine slap.

    It is also possible that the dip in the oil level also exposed your cylinders to damage where the piston crowns may have burned a bit and may have gone out of round like the bearings. And, while this is only ever so slight, the pistons can also become a bit eccentric in shape and instead of moving smoothly up and down the cylinders, they will slap a bit against the cylinder walls. The same is true of rings which can easily become eccentric and instead of holding the piston close to the side of the cylinder where they seal the cylinder and scavenge any leftover oil, they also tend to favor one side and can also slap against the cylinder wall.

    You can see then, it is important to keep checking the oil and not allowing it to fall below the recommended level from your car’s manufacturer. It is also important to change it as the intervals recommended by the manufacturer as well. In general, the old oil change knowledge and standard of changing oil and lubing the chassis at 3,500 miles is still a good rule to follow.

    However, if you can’t follow the 3,500-mile standard, using a 5,000-mile rule will also work as most manufacturers recommend that as the right oil change interval. Some even recommend 7,500 miles but, in my opinion, that’s really stretching it. I hope this helps.

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