Diagnosing engine noise

[Carolyn]

We see lots of posts from folk trying to get help with this 'knock' or that 'rattle'.  Last week I was listening to a 1ZZ with an intermittent loud rattle that was hard to locate. I won't go into all the symptoms, but suffice to say that. after much stethoscoping (a very cheap and useful tool), and having three time -served mechanics listen to it, we were only able to conclude roughly which part of the engine it was coming from.  

If you seek advice on the internet the responses will be no better than educated guesses.  Putting up a video with the sound of the fault is not a lot of help either, as the sound quality will be to poor to be of much use.

If one listens all around the engine, with a stethoscope, the general area can almost always be identified.  Then the only thing to do is to open up the part of the engine under suspicion and inspect the components.  Some noises (like pulley bearings) will be easily isolated with a stethoscope.  More internal noises won't.

This particular engine was rattling in the region of the timing gear and case.  When I opened it up, it turned out to be a stretched chain and damaged timing gear.  It could have been the oil control valve, it could have been the VVTi hub on the end of the cam, it could have been a blocked oil-way.  All those possibilities had to be checked and eliminated. (There could have been more than one fault causing such a rattle.)

I won't go into the cause of the damaged timing gear (see: Understanding your chain tensioner in the 'How To' section).

There is no way this rattle could have been cured without inspecting the possibilities 'in the flesh'.  If you have a rattle or a knock and you're not a professional mechanic, get someone to listen for you.  Doubtless, somewhere in you neighbourhood there will be someone with the experience to assist.  Grey hair is a good sign!