nc211

Are there any TSB’s for 2020 X167’s that relate to the fuel pump? I have a sound that sounds like it’s coming from the fuel tank area. Its a thumping noise, happening more and more now. Really notice it when at idle.

Have you ever been sitting at the light and a helicopter is nearby, especially a hughey, in the distance. You can hear the blades, but can’t see it? Thats kindve what it sounds like.

I have never had to replace a failing fuel pump in any car ever, and I am 49 years old. Kind’ve of hard to believe i’d need to on a 3 year old car with 52k miles, always Costco Premium fuel. So i thought I would ask if anyone has any knowledge of TSB’s from MB related to a fuel pump or fuel system issue? Or, a thumping noise coming from the rear underside when the engine is running?

Thanks!!

gaheeb

We just got our 2021 GLS 450 out of the shop for the 3rd time for the exact same reason. Helicopter noise at low speeds and while idling. This time they determined it was a faulty transfer case after getting error code from Drive shaft and then transfer case. The transfer case was replaced. Hopefully that solves the problem.

nc211

Thanks Gaheeb, i hope that fixes it too!

but i have to be honest, ive never known a tranfer case to make noise when the car isnt moving. Considering the noise happens when sitting still, and given how loud it is, i am a little surprised they had to hunt for it 3 times on yours. Seems like they could put it on the rack, turn it on, and immediately find it? Ours sounds like it is coming from underneath towards the rear of the car, which led me to believe either the fuel pump or an actuator related to the air suspension. Bit since it goes away immediately when the engine goes off, and doesn’t make a sound when i raise/lower rhe car, i ruled out the air suspension.

But if it becomes a “throw parts at it” hunting game, then this car is gone asap. Minor issues, annoying as they are (seat tears, misaligned window track) I can live with for a first model year run. But failing transfer case or issue like that, 3 years and 52k miles later (when manual calls for fluid change at 60k)? Thats a no-go for me. If it is the fuel pump, then I am 100% expecting Mercedes Benz to step up with some goodwill assist since I am out of warranty. Thats just crap if they don’t, for a repeat customer. Fuel pumps don’t go bad that soon when they’re not abused or constantly run on empty. We never go below ¼ tank for the very reason to keep the pump cool and lubricated, in all of our cars.

gaheeb

After 2 48v battery replacements, torn front seats, and a window off track, all with less than 20,000 miles, it’s certainly not the ownership experience we were expecting. Good luck. The service has been good, but who wants to keep going back and forth to the dealership?

ricardo124

Curious if you identified the cause of the thumping noise. I'm getting a similar sound during idle and low speed (<5mph) on 2022.

nc211

Not yet. I have a trans fluid service right around the corner and figured I would take a look then. Doesn’t happen all the time. Not entirely sure what it could be, but think it is fuel related. Maybe one of those weird evap things for fuel fumes. Car drives fine like usual. Just odd noise.

EClassic

We have a 2022 GLS450 that has this noise at Idle AFTER the impeller recall was performed. The car has been in the dealership twice since the recall to solve the exact thumping noise that you talk about. It seems to happen at idle more often when the gas tank is full. We have been able to record the noise and the dealership initially claimed it was a loose clamp due to the recall work. I just went back yesterday and reviewed the problem with the technician who claimed it may be an evap line problem. I'll eat a bug if this isn't an impeller blade knocking against the fuel pump housing. It is also audible during hard throttle when accelerating up a hill. The pace, tone and throttle input fixing the issue all point to this. The dealership kept talking about what a massive job the impeller recall was so I'm worried they will do anything to avoid re-doing the job. I will try to add the file.

nc211

Impeller recall??

ours still does it every now and then too. Doesn’t seem to impact the way it drives, and we’re 4 years and 70k miles down the road with ours. Not sure we’re willing to spend the time and money hunting for it until whatever it is breaks to reveal itself.

EClassic

"Due to a deviation in the production process of a sub-supplier, certain fuel pump impellers might not meet the material requirements and thus certain batches of fuel delivery modules might not meet the durability requirements," the company said. "As a consequence, the impeller might deform and therefore come into contact with the fuel pump housing, leading to a mechanical resistance. In some instances, this could lead to a shutdown of the fuel pump. As a result, the vehicle could lose propulsion, which could increase the risk of crash or injury."
Mercedes says performance degradation may occur before the pump fails outright, and a malfunction message will display in the instrument cluster if adequate fuel is not being delivered to the engine. Once the deterioration reaches that point, engine performance will likely be tangibly impacted. Mercedes will begin notifying dealerships of the recall campaign immediately; customers should expect notices to arrive in August. autoblog.com

It sure sounds like an impeller hitting the side of the fuel pump housing. I am just worried that it will fail out of warranty and I will end up with a huge bill to fix it.

nc211

Thanks for posting! So recall coming this August then? I agree, it absolutely sounds like the fuel pump to me too, always has. Thought maybe a vapor purge valve at first, but it's definitely more mechanical sounding. The "distant helicopter" sound..

Man, MB is racking up the recalls now on this car! Got one sitting on my desk for some computer transmission module, hear another is coming over a faulty 48v ground wire thing, and now this one. Think I'll just wait for this one to go live and then put it back into the shop for all 3 to get fixed at once. Oh joy....

EClassic

This is the sound we are getting. I amplified the recording to make it easier to hear.

nc211

Yep, 100%, that’s the sound!!

EClassic

I'll dig my heels in a bit at the dealer on this and let you know what they do. I'm pretty sure the pump was installed incorrectly after the recall service. In looking at the pump and sending unit configuration, It seems likely that the pump was installed in the sending unit improperly and it is bashing around in the sending unit as it runs. Its a huge job that probably wont qualify for recall reimbursement from Mercedes, so I'm sure I'm going to get the "could not replicate" or "tightened something" excuse. My dealership is run by a ugly National conglomerate that runs by spreadsheet so I'm not hopeful. I begged my wife to avoid buying an American made Benz, but here we are. I think there have been 7 recalls on this thing and its not a new model.

EClassic

Dealership is back with a cause. They claim it is the fuel tank evap check valve ball that is loose and making the noise. The car is reporting no fuel so I assume the have emptied and/or removed the gas tank to work on the issue. The part will take a week to get to them. The sound definitely seems muffled enough to be coming from inside or near the tank so the location seems right. I cant find much information on the part that would be in that location. I'm happy they are digging into a big job. They initially responded with a "could not replicate". I will keep you posted.

mercedesbuff

I promise I'm not an Eeyore, and when it comes to Mercedes-Benz, most people would actually call me an evangelist. I'm on my 9th (W222) and 10th (X167) Mercedes vehicles now. I regret to say that I have never had to visit the dealership more, in a one-year period, than I have with the GLS. Granted, I've never owned a "first year" Mercedes before (it's a '20), so maybe I can chalk it up to that.

The dealership has managed to fully resolve numerous issues, except for two: The harsh downshifting is now thankfully somewhat improved, with the most recent transmission update, and the driver's seat ventilation fan is now hitting something inside the seat, which makes an annoying noise (fan blades actually contacting something in there...)

My wife love the GLS, since it is Brilliant Blue (only offered in '20 and '21). And thankfully she is oblivious to almost all vehicular issues, so I just keep telling myself: "She's happy, and I have my W222 to console me...

EWL5

Some might say masochist!
I'm in a similar boat. It was a grudge purchase for my wife: "Happy wife, happy life"!

I remember Mercedes' better days but those are as fleeting as planned Superchargers!

nc211

thanks for the updates!!! I too originally thought evap at one point as well. Had a Toyota that would make noises on a full tank while just sitting in the garage, off for hours. Turned out to be the evap of the fuel tank fumes too..

EClassic

Final update. The car was at the dealership for nearly a month. They were oddly silent with updates, saying they were waiting for parts. They did refer to "Mercedes warranty procedures", so I assume they were talking to the mothership about the job.
They ended up replacing the entire gas tank and any associated parts like the fuel pump and valves. They said there was a noise from the charcoal cannister after that job, so they replaced that as well. The end result is the noise has stopped, but I don't know what was causing it. I'm still betting it was the fuel pump banging around within the fuel sender housing but that's a guess.

nc211

One thing I learned on my W212, is that trying to fix something that isn't obviously broken to the point of not working anymore in these cars, can be maddening. We're not messing with this until it actually breaks since it's not obvious to what it actually is. I do think it's fuel related, but considering their comment about noise in the charcoal canister after they replaced all of that, tends to lead me back to the evaporator system for the fumes, and that Toyota Highlander we had for 7 years that would make funny noises while sitting it the garage turned off, which ended up being the evaporator system regulating the pressure in the tank. Sounded like it was broken, but never actually broke.

EClassic

Final final update... We were called by the dealership because a part they had ordered came in. I was happy to hear we would have one last chance at solving the issue because it was still present after the gas tank had been filled. One of the techs heard the noise while testing and recommended installing a new fuel pump. While performing that job they noticed the vent valve on the top of the fuel tank was deformed so they replaced it. Testing at the dealership came back positive so I hope this finally fixed the issue. I assume that the warranty work for the fuel pump caused the vent valve to be pinched when they re-installed the fuel tank. Perhaps this caused some pressure differentials in the fuel pump leading to the knocking noise. I understand this is a confusing case, so I have attached the latest w/o documents. Owners may want to think twice about getting that fuel pump recall done.


Pg 1 Fuel pump noise

Pg 2

Pg 3

nc211

Thanks for sharing all of this EClassic, very helpful info!!

End of the day, it sounds like perhaps it is related to the evap system, and perhaps the true recall ought to be the deformed vent valve itself.