wheelspk2131

Hello,

My 2012 c63 has 48,000 miles on it, totally stock car.

Only on warm-start up just for 1 sec as the car is about to start i hear a loud pinging sound like the car knocks asif it has bad fuel or bad spark plug, it does not sound like lifter rattle or tick.

this knock/ping only happens if the car is warmed up Never on cold start and is very audible from in side and our side.

https://youtube.com/shorts/p6peb_atfyU?si=oHxoyYSyO_tev8Ao

car idles very good and drives normally not pinging even at wot or accelerating but i do hear a faint bussing sound coming from the right side of the cabin as I accelerate slowly from 2500 rpms in gear only never when i rev in neutral gear or parking, even if i rev it i don't hear any knock its just only warm startup.

please help me figure out what this is as im really worried about it .

thanks

wheelspk2131

Anyone?

skratch77

Car sounds normal to me

wheelspk2131

i had this car for 2 years and this sound ( clunk/knock ) just before it fires up, sound comes from the right side head only ,maybe you cant hear it but everyone around me can. Its definitely not normal.

jonii

power steering reservoir is clogged.

wheelspk2131

yes power-steering pump is making whining sound but what does the power steering reservoir or the pump whine have to do with a knock sound on warm startup?

Kamal Clarke

Hi OP,

I think I heard a chirp/chirping sound just before it started. I have this problem on my M156 when the fuel injectors need cleaning/replacement. Check your fuel injectors for leaks/dripping. Normally I just change all 8 injectors and i'm good to go again. If you have a good fuel injector shop near you, you can have them test and clean them. I have also gotten away with just doing cosmetic cleaning as well.

Regards
Kamal