When I bought my 1991 318i in May, it was a nice clean example, California car until 2006, no rust. There was just one strange noise on the test drive - something that sounded like a rotational metallic interference, or a rattle against the header. At least something from down in that area.
I bought the car anyway, thinking that it definitely needed a clutch, and the noise was probably something in the bell housing.
I replaced the clutch with my dad. If you've done this yourself, you know how involved it is.
Noise was still there.
I then thought that it has GOT to be the chain rattling. I have the extensive service history, and there is no mention of a timing chain in the last 100,000 miles. So, I had the chain, tensioner, guides, crank gear, water pump, and thermostat done.
Noise was still there.
I changed out all the crap under the intake.
Noise was still there.
Maybe it's engine knock? Seafoam, techtron, valve cleaner, three different kinds of plugs.
Noise still there.
Finally, I took it to the giant local BMW dealer. The tech could not hear any ping.
I pulled on the throttle and got it up to about 2,000 rpm, where I'd been hearing the noise. HE REACHED DOWN NEXT TO THE VALVE COVER AND BENT THE HEAT SHEILD PROTECTING THE PLUG WIRES AND THE NOISE WENT AWAY.
The heat shield was rattling in a way that resonated through the valve cover in a way that sounded like "pennies in a jar," or the telltale sound of engine knock. It only rattled at part throttle around 2,000rpm and vaugely at 3,400rpm.
EVERYTHING ELSE WAS A RED HERRING.
I mean, I'm glad that I did all this maintenance, and had LOTS of quality time with my dad....but still...
...don't let this be YOU!
Topic: An Object Lesson in Self (auto) Diagnosis (Read 1832 times)