It is important that you listen to your engine noise occasionally.
The combustion engine is a complex mechanism that ignites an air-fuel mixture, which moves the pistons. The pistons are connected to the crankshaft, which in turn rotates the wheels of the car. If you hear a knocking sound under the bonnet that sounds like someone hitting your car with a big hammer, you could be suffering from rod knock.
You can confirm this by cranking up the engine – the noise will get louder. Some people refer to the problem as spark knock, engine knock or engine pinging.
What causes rod knock?
To understand what causes engine knock, you need some basic knowledge of the relationship between the pistons and the crankshaft. The piston moves up and down due to the ignition of the air-fuel mixture by the spark plugs. A connecting rod connects the piston head to the crankshaft. On the underside of the crankshaft, there are bearings that facilitate the movement of the rod and crankshaft. Oil lubrication is used to protect all moving engine components from overheating due to friction.
Rod knock occurs when the bearings wear and this causes the metal parts to collide. When this happens, you will hear a knocking sound. The noise increases when you turn up the car. They could also collide because the oil level in the engine drops, which leads to a loss of lubrication.
The rod knock is similar to the piston slap that occurs when the wrist pin is worn out and starts to wobble the cylinders.
You should never ignore rod knock, as the problem gets worse with increasing mileage. If the bearings continue to wear due to friction, they will get worse and worse, and eventually, they will detach from the crankshaft and blow out your engine.
Video of the sound of rod knock:
How to fix it
If you hear rod knock inside your engine, you must replace the rod bearings. Damaged rod bearings will in most cases also damage the crankshaft and rods. You may need some help measuring the crankshaft and rods before replacing the bearings to make sure they are not too badly damaged.
The main cause of rod knock is wear and tear on the rod bearings. Oil is used to lubricate all moving engine parts. Oil leaks can be caused by a cracked head gasket or a defective oil pump. If you do not have sufficient lubrication of the moving parts, there will be more friction between the parts, which will cause the engine to overheat.
You should stop driving your car the moment your car makes that knocking sound. A lack of immediate maintenance will result in further damage to pistons, rods, and crankshaft.
How to identify rod knock?
Rod knock is identified by a repeated rattling and knocking sound coming from the engine. The noise becomes louder the higher the engine speed. If it only occurs when starting the car, it could be a problem with the main bearing and not with the rod bearings.
Depending on the damage caused to the car, the mechanical costs can be considerable. If further damage to the engine has occurred, you will be forced to buy a new engine. You will need some mechanical ramps, an oil pan, an oil filter wrench, and a new oil filter to fix rod knock problems.
You will need the help of your mechanic to determine the extent of the damage. If the rod knock is due to an insufficient oil level, the following steps can be used to change the oil:
- First, drive the vehicle to the mechanical ramps. This should place the engine in a position suitable for repairs. Make sure that the handbrake is engaged.
- Place the oil pan under the oil drain valve and remove the oil plug. This will drain engine oil into the oil pan. Ensure that all oil in the vehicle has been drained properly. Replace the oil plug.
- Remove the oil pan and check your rod bearings for wear. This may require some skill and the use of a mechanic’s workshop manual. Have your mechanic do it for you if you are not sure how to.
Some vehicles have carburetors that you must clean to prevent the accumulation of dirt and other foreign particles. Dirt in the engine is a major cause of rod knock. If you do not eliminate rod knock the moment you start hearing it, you may have to replace the entire engine. Rod knock affects critical engine components such as rods, crankshaft, and pistons.
The biggest problem is when several bearings fail at once. When the bearings are completely worn out, the rods grind against the crankshaft.
Rod knock is caused by the rod bearings being worn out or if you have low oil pressure. There are several moving parts in the engine, all of which require engine oil to stay lubricated. When oil leaks, these moving parts rub against each other and cause excessive heating due to friction.
You can distinguish rod knock from other engine noises from the fact that it increases the moment you rev up the car. The first thing you need to do to remedy the rod knock is to replace the existing engine oil. This is a simple do-it-yourself process where you have to drive your car to a mechanical ramp.
Change the oil filter and pour in new engine oil. The noise should be reduced. However, if you notice that the noise gets worse even after changing the oil, this could mean that your bearings are irreparably damaged. There could also be other engine damage.
In this case, you will be forced to call your mechanic for further repairs or, in the worst case, be forced to buy a new engine. Rod knock is a serious engine problem that must be treated urgently at the moment it occurs.