Engine Knocking Geräusch (rattle knock sound)???
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GL63
Engine Knocking Geräusch (rattle knock sound)???
Owned this car since 55000 miles and have a tad over 100000 miles now. Suddenly have this Geräusch going on when it’s idling predominantly (I don’t hear it after it goes above 1000 rpm)…but it is there at idle.
Note:
cross posted. This was posted in the suv section of our forum under X166 last week…but no reply.
I assume nobody else has had this issue?
Have always followed regular oil change and maintenance intervals.
This engine has no codes and no issues otherwise. Seems to run fine shall i suspect this is somehow a noise anyone else here has heard??
Note:
cross posted. This was posted in the suv section of our forum under X166 last week…but no reply.
I assume nobody else has had this issue?
Have always followed regular oil change and maintenance intervals.
This engine has no codes and no issues otherwise. Seems to run fine shall i suspect this is somehow a noise anyone else here has heard??
Last edited by MB18436572; May 19, 2025 at 02:15 AM.
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Sounds like a bad spitzer valve, bad muffler bearing, low on blinker fluid, or your 40 weight ball bearings are shot. JK, it's really hard to tell anything from a video online. Whatever it is, doesn't sound good. Have you tried to use a mechanic's stethoscope to find where the sound is coming from?
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GL63
So the prior poster appears to be on the right track. Recently the problem has gotten worse and was accompanied by a random misfire P0300 code and P00087 low fuel pressure. What the poster is saying is towards the rear of the engine is the high pressure fuel pump (M157) and it appears that these have failed. They typically can make that dreaded rattle noise. The issue here is troubleshooting what caused it. There is of course the low pressure fuel pump and tbh I will need to check fuel pressure to ensure the fuel pressure provided by the low pressure pump is within specifications because YouTubers have commented that inadequate low fuel pressure can actually cause failure of these high pressure pumps. Symptoms are that the vehicle drives fine seems great “except” when you get into boost at wot and caution you can destroy an engine piston in a case like this. No I have not done the work yet as right now the wife drives the car leisurely.
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GL63
Update:
source of noise is the high pressure fuel pump(s). One has failed now need to replace both of them, root cause is failing low pressure fuel pump.
Cost impact $4700 labor and materials. Reason being low pressure pull replacement requires removal of exhaust system and drivelines and gas guzzling the tank to remove it from the vehicle and replacing the pressure sensor and fuel pump/filter and at engine side replacing both high pressure pumps.
Mercedes did away with fuel pump access portholes,
I have elected to do this job myself and am adding the porthole and swapping all three pumps.
source of noise is the high pressure fuel pump(s). One has failed now need to replace both of them, root cause is failing low pressure fuel pump.
Cost impact $4700 labor and materials. Reason being low pressure pull replacement requires removal of exhaust system and drivelines and gas guzzling the tank to remove it from the vehicle and replacing the pressure sensor and fuel pump/filter and at engine side replacing both high pressure pumps.
Mercedes did away with fuel pump access portholes,
I have elected to do this job myself and am adding the porthole and swapping all three pumps.
Thread Starter
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GL63
One more thing this issue impacts all M157 engines. If you’re hearing the dreaded “tik tok” noise from top of engine under passenger side air filter (that’s the location of the high pressure fuel pumps) expect a minimum of $500 for both Bosch pumps at Rock Auto
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Thread Starter
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GL63
One more thing.
Fuel systems are complex. I forgot to mention I also updated or changed out the fuel rails on my M157. I will add that the fuel pressure was definitely “low”. The low pressure pump in tank was changed out (see my separate write up on how I accessed the pump without dropping the tank). The high pressure pumps were changed out which “improved” but did not completely eliminate the noise. As a final measure I changed out the fuel rails sourcing a pair of donor ones from an online reseller (not the dealer).
What perplexes me is what may have been the “root cause” of this issue in the first place. My final
comment to you is don’t go changing your high pressure pumps reading this if it’s not those to begin with. I had some sort of migration of “clogging” basically impacted the pumps and fuel rail. If you’re able to get access to some sort of fuel measurement device and record real time data that’s best. Diagnose and determine what’s likely the culprit. I don’t want readers to correlating what I have said to their auto and replacing thousands of dollars in components without determining which component actually failed, as an example I elected to replace both high pressure pumps meanwhile it diminished to noise but didn’t cure it. It did rectify my low pressure fault code but I didn’t stomp onto the the throttle to verify that was actually due to the low pressure pump. I will add the noise was completely gone only once I replaced the fuel rails. I am still perplexed through as I could not afford a new pair of rails and used a salvage yard. What’s the root cause??? Bad gas….wrong octane gas??? Want to ensure to avoid this issue again in future.
Fuel systems are complex. I forgot to mention I also updated or changed out the fuel rails on my M157. I will add that the fuel pressure was definitely “low”. The low pressure pump in tank was changed out (see my separate write up on how I accessed the pump without dropping the tank). The high pressure pumps were changed out which “improved” but did not completely eliminate the noise. As a final measure I changed out the fuel rails sourcing a pair of donor ones from an online reseller (not the dealer).
What perplexes me is what may have been the “root cause” of this issue in the first place. My final
comment to you is don’t go changing your high pressure pumps reading this if it’s not those to begin with. I had some sort of migration of “clogging” basically impacted the pumps and fuel rail. If you’re able to get access to some sort of fuel measurement device and record real time data that’s best. Diagnose and determine what’s likely the culprit. I don’t want readers to correlating what I have said to their auto and replacing thousands of dollars in components without determining which component actually failed, as an example I elected to replace both high pressure pumps meanwhile it diminished to noise but didn’t cure it. It did rectify my low pressure fault code but I didn’t stomp onto the the throttle to verify that was actually due to the low pressure pump. I will add the noise was completely gone only once I replaced the fuel rails. I am still perplexed through as I could not afford a new pair of rails and used a salvage yard. What’s the root cause??? Bad gas….wrong octane gas??? Want to ensure to avoid this issue again in future.
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One more thing.
Fuel systems are complex. I forgot to mention I also updated or changed out the fuel rails on my M157. I will add that the fuel pressure was definitely “low”. The low pressure pump in tank was changed out (see my separate write up on how I accessed the pump without dropping the tank). The high pressure pumps were changed out which “improved” but did not completely eliminate the noise. As a final measure I changed out the fuel rails sourcing a pair of donor ones from an online reseller (not the dealer).
What perplexes me is what may have been the “root cause” of this issue in the first place. My final
comment to you is don’t go changing your high pressure pumps reading this if it’s not those to begin with. I had some sort of migration of “clogging” basically impacted the pumps and fuel rail. If you’re able to get access to some sort of fuel measurement device and record real time data that’s best. Diagnose and determine what’s likely the culprit. I don’t want readers to correlating what I have said to their auto and replacing thousands of dollars in components without determining which component actually failed, as an example I elected to replace both high pressure pumps meanwhile it diminished to noise but didn’t cure it. It did rectify my low pressure fault code but I didn’t stomp onto the the throttle to verify that was actually due to the low pressure pump. I will add the noise was completely gone only once I replaced the fuel rails. I am still perplexed through as I could not afford a new pair of rails and used a salvage yard. What’s the root cause??? Bad gas….wrong octane gas??? Want to ensure to avoid this issue again in future.
Fuel systems are complex. I forgot to mention I also updated or changed out the fuel rails on my M157. I will add that the fuel pressure was definitely “low”. The low pressure pump in tank was changed out (see my separate write up on how I accessed the pump without dropping the tank). The high pressure pumps were changed out which “improved” but did not completely eliminate the noise. As a final measure I changed out the fuel rails sourcing a pair of donor ones from an online reseller (not the dealer).
What perplexes me is what may have been the “root cause” of this issue in the first place. My final
comment to you is don’t go changing your high pressure pumps reading this if it’s not those to begin with. I had some sort of migration of “clogging” basically impacted the pumps and fuel rail. If you’re able to get access to some sort of fuel measurement device and record real time data that’s best. Diagnose and determine what’s likely the culprit. I don’t want readers to correlating what I have said to their auto and replacing thousands of dollars in components without determining which component actually failed, as an example I elected to replace both high pressure pumps meanwhile it diminished to noise but didn’t cure it. It did rectify my low pressure fault code but I didn’t stomp onto the the throttle to verify that was actually due to the low pressure pump. I will add the noise was completely gone only once I replaced the fuel rails. I am still perplexed through as I could not afford a new pair of rails and used a salvage yard. What’s the root cause??? Bad gas….wrong octane gas??? Want to ensure to avoid this issue again in future.
This explains the progressive nature of the issue and why replacing components downstream (the pumps) only improved it, while replacing the clogged rails finally fixed the noise. The salvage rails worked because they were clean.
To avoid it in the future, always buy top-tier gasoline from reputable stations and consider replacing your fuel filter (if your model has a serviceable one) at regular intervals as preventative maintenance.
