bennelson972

Guys/Gals,
I'm down a car and have to get the sending unit replaced in my 06 CLK 500 today. I have been searching for about two hours now (at work mind you) for detailed instructions on how to get the sending unit fuel line clamp off (it is a crimp ring). I have had no luck. Can someone please point me in the right direction here? Specifically - how to get the fuel line off the old sending unit and reattached to the new one. Everything else I got. TIA.

Plutoe

search for "clic A" pliers!!

bennelson972

Well this isn't turning out to be as easy as I thought. Do I have to take the fuel pump out as well, in order to replace the sending unit? I've got the fuel line disconnected from the sending unit and the sending unit itself is pulled out about 8 - 10 inches and then the hoses and various wiring appear to be stuck and I can't pull them any further to disconnect them.

Again, TIA to anyone who can help with this

bennelson972

Figured out I have to access the fuel pump as well. I have everything disconnected from the fuel pump with the exception of one hose. Can someone tell me how to get this connector off?

How do I remove this from the top of the fuel pump? This is the new one.

Rudeney

I had the same problem. It's supposed to just be a snap collar, where you push in on the connector, pull back on the collar and it releases. It's like these "shark-bite" plumbing connectors. However, it seems that the seals like to fuse themselves to the nipple and not come loose, and the nipple on the pump gets brittle. I ended up breaking the nipple on mine, requiring a whole new pump. I would remove all the lines you can, then cut this last hose off a few inches from the pump so you can remove the pump from the car. Take it to a work bench and then carefully remove it there. Just cut the connector apart piece by piece if need be.

bennelson972

Rodney, that is precisely what I did. I have finally gotten everything installed. The only problem I'm having now is I can't get the big black threaded retainer ring to thread properly and tighten down the sender unit. Any thoughts on this? The one over the fuel pump went right on which, oddly enough, was the one I had the most trouble getting off.

Rudeney

It doesn't "thread" - it should just snap on and click in place.

bennelson972

It's threaded. Both rings are threaded. I'm referring to the big black ring. Here's a pic

bennelson972

It appears the sending unit and seal are both seated properly so I have no idea what is keeping the retaining ring from threading on properly.

Rudeney

Oh, sorry - I misunderstood and thought you were still having problems attaching the pressure line to the fuel pump. So, you are having problems getting the retaining ring started on the sender unit? Did you get the ring on the fuel pump in place? They are the same - same part numbers and everything. Make sure the sender is installed correctly - there is a dimple that lines up with an arrow on the tank.

bennelson972

I finally got it on after struggling with it for over an hour. It's very frustrating to be that close to finishing a job and being stymied by a plastic ring.

Thanks for your help Rodney.

Rudeney

Glad you finally got it back together. My CLK had the "California" version, which was a giant hose clamp instead of the screw-on ring. I had to use a "Skewdriver" to get to the screw head. It was a major PITA.

Ptrigg17

Apparently I have the same version because I screwed that ring around 20+ times and nothing happened so I finally caught on that I had toreally release the clamp I got everything off however getting it back together is another story I can't seem to get the sending unit seated . Is there some sort of alignment issue?

Ptrigg17

After an afternoon of frustration I thought I would share what I think I figured out about replacing the fuel sensor gasket. If your car is leaking at the top of the sending unit first check to see if your cover is secured by a plastic ring and a hose clamp around the perimeter. This is how my MY 09 550 was configured, I believe that means it is a California version but I am not sure. In any event the securing ring was clamped on not screwed on. It took me about 1 hour of spinning the securing ring and getting nowhere before I removed the hose clamp and the securing ring came off. I was not able to fully seat the sending unit with the new gasket I purchased so I decided to throw in the towel after another frustrating hour of my life and put the old gasket back in. I was able to tighten the clamp and securing ring much more than it was at the start as evidenced by a smaller gap in the securing ring . I filled the tank and no more leak! I am not sure if this will be a long term fix but for now all is well.
So the moral of the story is , if your car is configured like mine with a clamp around the outside of the securing ring your first action should be to tighten the clamp if possible and see if the leak stops. By the way a 7 mm box wrench is the tool I used.

Rudeney

The new gasket is thicker, but I was able to get mine in with a bit of grease on it to help is slide in place so it didn't pinch and bind. That ring and clamp is a total PITA to deal with, though.

faded1004

holy hell yea... those clamps were a pain. i just did mine 2 weeks ago.

those clamps took me a good 25 minutes each on and off. so i had a friend help me.

btw, on my car... the seal wasn't leaking. after replacing the seals... thinking i was done...

i found my housing... the white part. there is a raised part in the middle that is glued. it was leaking from there. i attached a pic of my new part and circled where my leak was coming from. only when tank was full and very light while driving. when i stopped the car, the fuel seemed to continue to puddle. after replacing the seal, i filled up the tank and sat there checking it with everything apart. filling my tank didn't make it leak. it was after driving where i started to notice it.

so lame... i had to take of those clamps twice!!!

i was getting a light gas smell in the garage the morning after i fill up my tank. filling up half way to about 80% didn't make any smells.

when i looked under the car, i noticed white liquid dry marks on the driver side plastic panel. i attached a picture of that also. after this repair, i now know it was fuel making those marks... kinda splashing on my rear portion of the exhaust... super dangerous.

tips, i also used alittle lube on the seal putting it in. wd40. took alittle time. but it did all go in together. i had to also use a double wobble deep socket setup with a small ratchet.

i bought the gaskets on ebay, oem. supposedly... and my gaskets were not just alittle thicker... but it was like 2x to 3x taller! i am hoping i won't have to do this again. i hate touching fuel systems

Ptrigg17

Faded1004 says he had multiple clamps, I had only one large hose clamp that squeezed the split securing ring, others have some sort of screw ring. How many different set ups are there? I purchased a tool to unscrew the ring that I assumed held the sensor in place but I did not need it . What I needed was a contortionist to access the head of the hose clamp to unscrew it . Two days after I spent an afternoon cramped into that small area I still have pain in my lower back and shoulders. I am thankful that my 09 is a cabrio, I can't imagine what this would have been with the coupe.

Ptrigg17

After many hours crammed into the back seat area attempting to repair the fuel leak at the top of the sending unit by replacing the seal, I discovered that the leak was located at the same spot as represented by Faded1004 in his photos. I decided to try an epoxy repair rather than spending $300+ for a new unit. So far 2 fill ups and no fuel leak. JB Weld to the rescue. Cost $0, it was in my tool box, time 15 minutes. Thanks again to this forum where the epoxy repair was mentioned.

trikoid

I have the same problem! I narrowed down the leak to the area faded1004 circled in red.

My situation is shown in below pic. Driver's side rear seat.

Also attached is the cover that is over the bolt. I almost broke the plastic piece since I just tore it off. With some more finesse, you can avoid damaging it.




I am going to try the epoxy route. Any recommendations for epoxy? Is JBL weld really the best, or I use some plastic-like version?

Anker

My experience is that epoxy exposed to gasoline turns brittle and cracks, resurrecting the leak.

trikoid

Rudeney

It's the pressure sensor that leaks. It's not a separately replaceable part, so the whole sender unit must be swapped. Stupid me, when I replaced mine, I meant to keep the bad sender and see if the pressure sensor could be removed and its seal replaced, but I didn't. Maybe an enterprising member who does this swap will take a closer look.

insame1

I found that you can replace the pressure sensor on the new version of the sending unit. I just did it on my clk55.

Rudeney

Where did you get the part? I can't find an individual part number for it in EPC. And did that fix the leak, or did you just have a bad sensor?

trikoid

The epoxy did the trick. No more leaking. I'm not a wizard with the epoxy, which is runnier than I hoped for the first two minutes (5 minute JBL plastic weld), but there is at least a millimeter over everything. I used some metal tape I had and tried to make a dam with it so it would just go where it had to.

After epoxy