What's wrong with this engine? (video)
 

1999 911 Cabriolet, loud tapping noise on drivers side. Car runs and drives, doesn't smoke.

What do you think is wrong?

Video doesn't work for me?

I can't really tell from the video, since I have minimal sound. Is it throwing any codes ? I wouldn't recommend driving it until your able to figure it out.

Difficult to tell from the audio how much of that is exhaust and what part is mechanical; but it really seems to have the potential to be very serious - as in don't run the engine & have it towed in serious. GL & post further diagnosis.

The noise is about 8Hz @idle => coinciding with one of the cylinders. Hopefully it's just a loose spark plug. +1 on not driving it till it's been looked at.

Hope it's just a manifold gasket maybe? But I don't really think it is, its most likely terminal to be honest :-( piston slap due to bore wear? hope I'm wrong.

that is a lot of noise coming out from there.. not sure if they are exhaust related noise like misfiring or mechanical noises though...

Yikes. That sounds like a rod or a piston since the sound gets louder as you accelerate. Doesnt sound like a bad valve. Could be an exhaust leak, I would start there. How is your oil pressure? If the pressure is low, that indicates a rod.

Take the oil filter out and check for metal. If there is metal in it, not good.

No CEL? No smoke? Vital fluids ok?

Do not start the engine again, just to be safe. Flat bed the car to a qualified shop and have an expert give a listen.

I am not a professional mechanic but the noise sounds like one horrific exhaust gas leak (but it could something else though equally as benign (though you do not want to let this go at all!).

My thinking is if the noise was really really something serious internally the engine would be showing more than just the noise about now.

Sounds like a GIGANTIC exhaust leak.... Im optimistic! :thumbup:

Dang, pretty "ballsy" to drive the car with it sounding like that. Best of luck getting it sorted out.

P.S. The rythmic staccato reminds me of the sound made by small engines used on outriggers

That sounds like really bad rod knock; I certainly wouldn't drive the car. Shouldn't be lifters or valve train, the frequency is too slow.

How in the world would that be manifold gasket related?

Much like all the other posters. Stop driving that car. Does the sound become louder at the rear with the engine lid opened? Get it into a garage for a better diagnosis. It sounds awful and would scare me half to death if it was coming from my car. Best of luck.

Combustion leak... Probably a loose spark plug, or you blew a chunk out of a head.. PLEASE DO NOT START IT AGAIN!!!!!! It is very easy to drive these engines to death and a simple issue can become a huge one in just a few seconds.

No noise is a good noise, especially under load...

Sounds like a GIANT exhaust leak!