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2009 SLK 55 AMG
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966 Posts
Discussion Starter #1
DansSLK/et al

Hi Dan/all,

Here is the continuing saga of the ticking/clicking/tapping sound of my engine with a so far happy ending:

Fyi: not associated with engine whine in previous posts.

To recap:

For about a month’s duration (mid feb-mid mar), I have had an intermittent engine squeak. The sound closely resembles the sound your metal belt clasp would make when striking your pants metal belt buckle over and over or a rock that would be inside a hubcap (No hubcaps). The sound would be there at any speed and even after stopping the car with the engine running in park so I ruled out wheels, etc. I have had the brakes inspected anyway by Mercedes and therefore ruled out pads, calipers and rotors. The sound sometimes shows up after my morning commute of 25 miles/20 mins. But usually, after parking the car after a trip where the car is at normal operating temperature 95 c for about 1 hour, the sound returns and after approximately ten minutes it disappears, after car engine goes down to 80 c not to be heard again until this scenario is repeated. The one time I was fortunate enough to be at the Mercedes dealer when the sound occurred a passing mechanic said, "That is your pulley". They replaced the 'v' pulley and the sound returned the next day. Last week I had the dealer test the radiator electric fan and air pump and there was no noise. The purge valve was also checked. The sound was still there after leaving dealer.

So since mid-march everything is great. No noise. Then in April, after 4 weeks of no noise, the ‘check engine’ light comes on. What they hey!!? Since I am familiar that if the gas cap is not tight, you may get a ‘check engine’ error message I retighten cap. Light does not go out. This is a Saturday about 10 am and mb service is open. Off I go.

After having the car for 1 and a half hours, the tech brings the car around and he says it was the gas cap. I say, ‘hold on there’. I checked the cap. He said, “It is not that the cap is tight, it is the gasket inside that needed lubricating”. He removes the cap and boy could you
now hear the pressure escape. There is also a noticeable difference closing the cap.

So Dan/all, here is my question:

Could the issue with the gas cap gasket/seal not sealing properly have in some way contributed to my original engine squeak? By that I mean, if the gasket/seal was intermittently sealing the pressure I got no noise but when it was NOT sealing the pressure I got the squeak? My logic is that with fuel injection, maybe air was causing something to not do something and that is why it made the noises (that is about the extent of my knowledge with fuel injection).

Thanks Dan and all for any input to this mystery. All I know is that I am squeak free for about 6 weeks now.
 

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2009 SLK 55 AMG
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966 Posts
Discussion Starter #2
dansslk reply from slkworld forum:

It shouldn't have really because the fuel is drained from the bottom of the tank it also used as coolant for the pump the pressure downstream of the pump should be unaffected by a loss in the tank so long as there was a big enough head of fuel to keep up the flow rate into the pump if air was in the system it would have shut down either from the pump overheating and tripping off or from the ME killing it because the engine would be misfiring badly.

The tank pressure is only used by the evap emissions system if the tank is very low on fuel the pressure can help keep the flow rate up but you would have to be running on empty for it to get that bad to be honest.
 
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