mokawop

I recently purchased a 2020 c63s sedan with 14000 miles. I never noticed until recently, but the engine makes a tick or a clacking sound around the left and right intake area upon startup. It only happens on cold start or if the car has been sitting for more than 3 hours, and it only happens for maybe 20 seconds or less. It's not that loud, and with the hood closed you don't hear it at all. I think it's normal but I'm paranoid and it's never safe to be sorry so I wanted to see what you guys thought. I have included videos below.


https://youtube.com/shorts/dp8bQgtxsZE?feature=share

https://youtube.com/shorts/HSn_CwIjRZ0?feature=share

https://youtube.com/shorts/29Ai6u2pv8s?feature=share

mokawop

I just wanted to add that the sound is faint but still noticeable if the hood is open. I would also take it to warranty, but recently the dealership takes over 2 weeks to even take a look at the car, so if it is a normal noise and Im just being paranoid, I would have left my car sitting at the dealer for nothing.

koifysh

Thats the purge valve 100% if the noise is more noticeable on the driver side. You’ll be fine for now but those purge valve are known to go bad. I changed mine as it was getting too noisy and was causing check engine light, rough idle.. After replacing it, no more noise and engine is smooth as butter

superswiss

Sounds all normal. The primary ticking sound are the injectors. Injecting the fuel under high pressure makes a noise. Initially the engine has a higher idle for about 30 seconds or so after cold start and there are some other noises for a while that eventually settle once everything is running round. It's just the cold engine waking up.

mokawop

Thank you! Just wanted to be sure since these cars make so many noises haha

BinkyTheToaster

FYI, to improve longevity of the motor for cold starts, switch the ignition to "On" prior to starting. This engages all the electric pumps for water, fuel, and most importantly, oil. That way it's not a dry start on top of cold.

superswiss

I'm not sure there's much to this. The pumps prime when you open the door. You can even hear it.

BinkyTheToaster

I think that's the fuel pump. The oil pump consumes far more power, and doesn't run until the ignition is switched on. Also, you can't really "prime" the oil pump in the way the fuel pumps come up to pressure. Oiling's not a closed system, so the pump has to run continuously to keep pressure. Leaving the door open when you hit the button, you can't miss it.

superswiss

That's possible, but even so. With the push button start it goes through the priming before it starts the engine. You can also hear and observe it from the outside if you use remote start. Once the command is received it goes through priming before the engine fires up. When starting the engine from within, there's a delay between pressing the button and the engine actually starting. Don't think you gain anything turning on the ignition first. The only reason to go through ignition on first is if you want to change the drive mode and fire it up in S+ or Race. However with the FL you can press and hold one of the shift paddles and then engine start to trigger the Emotion Start.

BinkyTheToaster

Eh, six of one, I suppose, I just know that the time between pushing the button with the car off, it fires up real quick. Personally I felt that it wasn't quite long enough; I'll have to throw my scan tool on it and datacap the pressure sensor, see what the curves look like versus time-to-fire. In the end it probably doesn't matter given that these engines have roughly an 80k mile rebuild interval.

mokawop

I swear this is the last time haha, I've recently noticed that the sound actually comes from the rear of the engine. I believe the fuel pump area? I just want to make sure it isn't that timing chain bs. I've attached a video below. It's much easier to hear it on your phone and in person the tick is very pronounced. It's not the purge valves as I know that's from the front driver's side. It happens once the revs come down on cold start, and disappears after a minute or two. If anyone has any thoughts please let me know.

https://youtube.com/shorts/2vdRRgHe59c?feature=share

mokawop

Noise was resolved under warranty, turned out to be a faulty fuel pump.

W205C43PFL

Hmm there is a fuel pump recall for many MB models...but might had been about an entirely different issue.

mokawop

Who knows, but it fixed my issue so Im glad its not anything more severe.

W205C43PFL

For sure : )