Shock Horror

[jackabea]

Hi All just an introduction, 63 yrs old in to Cars and just had a Z3, the shock horror part is that on the way home the other day there was a knocking noise developed from the engine compartment, to me it sounds like a big end gone, however various people are telling me "I have never known one of those fail" and suggested altenator air con unit etc, this does not sound like any of those but maybe? i am unsure, a little confused with all the input
So i came to the experts! you guys, any help would be great.

Thanks in advance and anticipation of course.

- - - Updated - - -

Sorry forgot to mention it is a 3 Ltr petrol.

[one wolf]

1. Video tape it with your phone
2. Upload video to youtube
3. Provide link in this thread

[Cobra1956]

Did you open the hood? A/C should not be turning if off unless the clutch is stuck. Alternator would be brushes and could be a bearing but doubt you would get knocking. My guess is that if it is that loud you will find out where it is pretty fast. If you want to get really crazy you can take the belts off and start it eliminating the other two items

[z3forlife]

Check for loose spark plugs

[zellamay]

I was convinced I had a rod knock for a couple of days. I know engines a bit, so I'm not a novice. It sounded like a knock, but duller. I found 3 loose spark plugs, one a couple of turns.

[Cobra1956]

That's crazy! Just vibrated loose or not torque enough in the first place?

[zellamay]

That's crazy! Just vibrated loose or not torque enough in the first place?

D. All of the above. .............. Apparently, I suffered from "fear of stripping out aluminum heads" syndrome. I did that once on a 1965 BSA Lightning.

[z3forlife]

So .... what's the verdict

[jrkoupe]

yup...could b plugs.....could be a chunked belt...it sounds awful