2012 S550 Clunk/Thud Sound From Rear At Start-Up
Thread Starter
Member
Joined: Jun 2018
Posts: 146
Likes: 31
From: Stuart, Fl
2008 S550
I truly appreciate all the advice and suggestions. I am so stoked I found the problem this weekend and fixed it this morning! It turns out it was the fuel filter and I was only able to pinpoint it by removing the back seat and the inspection plate and actually put my hand on it and had my wife start the car and I instantly felt/heard the thump/clunk and knew that was the problem. Ordered a new one and replaced it this morning...pretty straightforward and easy and it's perfect no more sound! Hope this helps someone else on the Forum.
BTW, there are two round inspection ports under the rear seat the one on the driver side is the fuel filter and the one on the passenger side is the actual fuel pump. These are mounted right on top of the fuel tank very easy to access.
BTW, there are two round inspection ports under the rear seat the one on the driver side is the fuel filter and the one on the passenger side is the actual fuel pump. These are mounted right on top of the fuel tank very easy to access.
Last edited by Polo35m; May 13, 2024 at 12:07 PM.
I truly appreciate all the advice and suggestions. I am so stoked I found the problem this weekend and fixed it this morning! It turns out it was the fuel filter and I was only able to pinpoint it by removing the back seat and the inspection plate and actually put my hand on it and had my wife start the car and I instantly felt/heard the thump/clunk and knew that was the problem. Ordered a new one and replaced it this morning...pretty straightforward and easy and it's perfect no more sound! Hope this helps someone else on the Forum.
BTW, there are two round inspection ports under the rear seat the one on the driver side is the fuel filter and the one on the passenger side is the actual fuel pump. These are mounted right on top of the fuel tank very easy to access.
BTW, there are two round inspection ports under the rear seat the one on the driver side is the fuel filter and the one on the passenger side is the actual fuel pump. These are mounted right on top of the fuel tank very easy to access.
Thread Starter
Member
Joined: Jun 2018
Posts: 146
Likes: 31
From: Stuart, Fl
2008 S550
Yes sir that is correct I replaced the fuel filter assembly which is on the rear driver side under the back seat. I guess there's some sort of check valve in there which must have been worn out and causing the fuel to lose Prime and then subsequently clunk on Startup. I wound up getting an inexpensive aftermarket went on Amazon less than 50 bucks! The fitment was absolutely perfect and it was pretty easy to install but a couple of tips.... use a tiny flat blade screwdriver to push in on the various electrical plugs for easy release. Also the smaller diameter of the two fuel hoses is under pressure and I got a nice spray of gas in the face. If you put a rag around it you can avoid this. Also releasing the smaller diameter fitting was quite difficult because it was under pressure the detent tabs did not want to release but you have to push it in really hard then squeeze the detent tabs and it comes right off. And finally I had to take a small flatbread screwdriver and sort of push the detent tabs back out so that it would catch when assembling on the new filter assembly. Same goes for the three electrical plugs, I just gently pushed in on the detent tab so that it would catch and stay snapped.
Yes sir that is correct I replaced the fuel filter assembly which is on the rear driver side under the back seat. I guess there's some sort of check valve in there which must have been worn out and causing the fuel to lose Prime and then subsequently clunk on Startup. I wound up getting an inexpensive aftermarket went on Amazon less than 50 bucks! The fitment was absolutely perfect and it was pretty easy to install but a couple of tips.... use a tiny flat blade screwdriver to push in on the various electrical plugs for easy release. Also the smaller diameter of the two fuel hoses is under pressure and I got a nice spray of gas in the face. If you put a rag around it you can avoid this. Also releasing the smaller diameter fitting was quite difficult because it was under pressure the detent tabs did not want to release but you have to push it in really hard then squeeze the detent tabs and it comes right off. And finally I had to take a small flatbread screwdriver and sort of push the detent tabs back out so that it would catch when assembling on the new filter assembly. Same goes for the three electrical plugs, I just gently pushed in on the detent tab so that it would catch and stay snapped.
