Hi, my wife's car has developed a knocking noise and sounds like it's coming from the piston area.

A couple of months ago the oil light came on and we had the oil strainer cleaned out, did 3 oil changes and ran some oil cleaner through it. Last month the alternator belt went so I replaced that and now we have this noise. I please see the video I've uploaded.

Any ideas?

Thanks in advance


https://youtu.be/dI5VKfdH08c

 

Hard to say, but it sounds more like an AC compressor issue to me.

 

So I'm thinking that's the diesel engine? Most folks like me in the US aren't very familiar with Mazda diesel engines (or any diesel engines for that matter), but I agree with Lobstah in that it sounds like it may be from a belt driven accessory. I like to remove the serpentine belt(s) when I have a noise I'm trying to track down and run the engine very briefly to see if the noise goes away.

 

That doesn't sound like a rod knock. More like a rotational mass that's got issues. Head over to the hardware store and get a wooden dowel rod about 2 or 3 feet long. Put your knuckle on the end then use your knuckle to press the cartilage on your ear opening closed. Your knuckle and the cartilage will make a sound chamber like a stethoscope. Press the other end of the rod onto your a/c compressor, the alternator and anything else you want to listen to. Your knuckle will also keep the rod from ramming into your ear if you hit something moving. So stay away from the belt.

If the problem is your a/c compressor for instance, you will know it for sure then.

Now, it MIGHT be an internal issue on the engine like a lower end noise. Not being there and being partially deaf, I can't say for sure. However, try the cheap thing first. If it works, you can fix it quick. If it doesn't, you're only out a buck or two. Usually though a rod knock sounds like a jack hammer and gets worse as you speed the engine up. Your noise just gets faster, that's why I think it's a rotational mass problem.

 

The sound is not distinctive and in the video you are moving far to fast to really conclude much. The sound needs to be narraowed down much better and the best way to do that is with ....
or something similar......
Mechanics Stethoscope (harborfreight.com)

 

If it is the 2.2 SH diesel engine, they are bad news.

Get the oil pressure tested.

 

I recently had that problem and it turned out to be the over head lifters, you can see more about it on YouTube and how to fix it as well