Engine Sounds - how to pinpoint them
Engine sounds vary from one vehicle to the next, but in general they should sound similar. They should sound smooth, not like a clicking, tapping or knocking noise. If they don't, then you'll probably want to know two things: where are they coming from; and, what's making the sound.
Knowing both will give you an idea of whether you will have continued interest in the vehicle.
Let's do two things here. First, let's talk about the kind of sounds one might hear, and then let's discuss how to pinpoint the origin of the sounds.
It's hard to describe engine sounds, but since most of us have heard them before, we probably know what a normal engine sounds like. So, we just have to identify abnormal sounds and what they might mean. Here's a list to consider:
Spark knock (also known as dieseling and pre-ignition) has a funny sound that I describe as marbles bouncing around inside one or more of the cylinders. It can sound a bit like a diesel engine too. It's caused by premature fuel ignition inside the cylinders. Largely it's a timing issue, but it could also be caused by carbon fouling inside the cylinders.
Rod knock is a distinctive tapping or clacking sound inside the top of the engine. It will clearly sound like a mechanical problem. It's caused by a push rod out of place or valve lifter failure.
Piston slap is rare, but it sounds like a milder case of rod knock, only deeper inside the engine. It's caused by worn pistons and cylinder walls.
Lifter noise is much more common and sounds like clicking inside the top of the engine. Lifters that are dirty, dry or sticky can cause this problem as they bang into the rocker arms.
Rocker arm problems can also sound a lot like lifter noise, but it will be a bit more pronounced, and can cause and engine to perform poorly.slapp crowns and inside the cylinders. Retard the timing and the spark knock will go away. prematurely
while driving and with the vehicle parked with the engine left running.let's talk, like a well oiled machine