Knocking sound for 10 seconds at startup
 

Helping a buddy out. Anyone had this issue before? Seems to be coming from towards the rear of the engine.
Length of the knocking varies with the cold weather so quesitoning if it s a oil thing. Checked for loose heat shields, bolts, the usual.

does it change whether or not youre on the clutch or with rpm?

Sometimes. It lessens when the clutch is pressed in/ let out or revved. Cant put the exact timing of what gets it to stop.

next time its cold, take the inspection plate off the bottom and start the car. just watch the clutch spin until it stops. its possible it could be coming from inside the transmission but i think you would notice something wrong if it were. how heavy of knock sound are we talking here? can you post a video?

Pretty heavy. Checking on the slave cylinder to see if the rod might be sticking or anything else. Ill try and post a vid

video attached.

no opinions?

thats not a knocking sound homie..... i dont mean knock in the technical term either. im saying it in the literal sense as in *knock knock*. thats a rattle. this is important because a sound like that is either an exhaust leak or a loose heat shield.

Sounds to me like a metal door rattling (heavier than a heat shield) - maybe the wastegate or similar.

I would try using a mechanic's stethoscope to locate the source of the noise. Or you can use a 3 foot section of garden hose, or even a large screwdriver as a listing device.

Yeah, we tried looking for a loose heat shield or bolt. Its strange because it goes away after a few seconds. Perhaps whatever is loose is settling.

exhaust leaks do that too

Can't listen to the video at work, but I would suspect the turbo control door in the exhaust manifold. If the actuator isn't preloading it slightly it will rattle when the car is cold and shut up once the car warms up and the metal expands.

Dale

Had a similar sound years ago when the clutch was depressed. It's possible that the front transmission cover has broken and is rattling around between the throw out bearing and the input shaft.

Jump under the car and open the clutch inspection plate, check to see if the cover has broken off.

https://cimg4.ibsrv.net/gimg/www.rx7...c0f342b670.jpg

Dale's definitely onto it here, it does sound very much like ceramic knocking against cast iron.

Thanks. Hard to tell through the inspection plate with the clutch and flywheel in the way. But i believe its gotta be in the clutch area. Sound goes aways after several clutch pumps.