fuel leak - Mercedes-Benz Forum
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post #1 of 13 (permalink) Old 06-13-2019, 02:24 PM Thread Starter
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fuel leak

I decided to change out the fuel line between the pump and the filter after finding that it was developing a lot of small cracks. It wasn't leaking or anything, but it looked like any easy opportunity to head off any future problem. So I've put the new line in - changed all the copper flat washers - didn't change the check valve - and cranked it all down tight. Now I've got a leak at the junction that will just not go away. I've tried tightening it further. I've pulled it apart and replaced all the recently replaced washers, It still leaks!! Any suggestions would be greatly appreciated. Just how tight should those joints be? Do I need to crush the washers? Thanks.
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post #2 of 13 (permalink) Old 06-13-2019, 02:39 PM
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Where did you get the washers? Standard copper washers won't work... they're not soft enough. You need official MB washers. I think Autohausaz.com carries them.
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post #3 of 13 (permalink) Old 06-13-2019, 04:37 PM
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Where did you get the washers? Standard copper washers won't work... they're not soft enough. You need official MB washers. I think Autohausaz.com carries them.
I know that OE only is the law of the land here but copper is copper.

The thing OP needs are metric washers which ensure that they fit snugly. Anything else and you run the risk of leaks. That's what autohausaz is selling. AutohausAZ are not getting a set of OEM washers blessed from the hands German machinists

I think I got a set of metric washers from harbor freight. Either way, any hardware store should have these in stock. Pick up a kit so you always have some on hand.
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post #4 of 13 (permalink) Old 06-14-2019, 07:24 AM Thread Starter
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Thanks for the input. I've been using copper washers from and assortment bought on Amazon and, yes, they're the right size - M8x12x1.5. I guess I'll pull it all apart and look to see if there's some dirt on one of the surfaces or if the check-valve or banjo are distorted.
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post #5 of 13 (permalink) Old 06-14-2019, 08:45 AM
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Not saying it will help but I took a scotchbrite pad and lightly cleaned the surfaces that come in contact with the washers before I put it all back together with new washers. This was with the entire assembly out of the car on my workbench. No leaks on my first try......maybe I got lucky
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post #6 of 13 (permalink) Old 06-14-2019, 10:11 AM
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Originally Posted by aml22ith View Post
Thanks for the input. I've been using copper washers from and assortment bought on Amazon and, yes, they're the right size - M8x12x1.5. I guess I'll pull it all apart and look to see if there's some dirt on one of the surfaces or if the check-valve or banjo are distorted.
You are experiencing the exact same problem I had. I too bought and assortment of metric copper washers from Amazon and the connection leaked. So I removed the (new) washers and replaced them with some more "new" washers from the assortment... same thing, leaked. I thought just like beast... copper is copper right? Wrong! There are many grades of copper and the type you need for your fuel connections are much softer than the ones you'll get in the Amazon assortment.

Do yourself a favor and save yourself some time in the process... order the washers from Autohuas and your leak will be gone.

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post #7 of 13 (permalink) Old 06-14-2019, 11:03 AM
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You are experiencing the exact same problem I had. I too bought and assortment of metric copper washers from Amazon and the connection leaked. So I removed the (new) washers and replaced them with some more "new" washers from the assortment... same thing, leaked. I thought just like beast... copper is copper right? Wrong! There are many grades of copper and the type you need for your fuel connections are much softer than the ones you'll get in the Amazon assortment.

Do yourself a favor and save yourself some time in the process... order the washers from Autohuas and your leak will be gone.
What's the grade of the copper you're using? The stuff i have from harbor freight isn't graded but I can bend it with my fingers.
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post #8 of 13 (permalink) Old 06-14-2019, 11:30 AM
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What's the grade of the copper you're using? The stuff i have from harbor freight isn't graded but I can bend it with my fingers.
I don't know the grade, I only know that the assortment of metric copper washers I bought on Amazon leaked and the washers I got from Autohaus didn't.

Maybe Harbor Freight sells soft copper washers.

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post #9 of 13 (permalink) Old 06-14-2019, 12:46 PM Thread Starter
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Are they supposed to be that soft? I’ll check em when I get home. Bend with fingers or are we talking pliers here?
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post #10 of 13 (permalink) Old 06-14-2019, 12:46 PM Thread Starter
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Ah, fingers .... I’ll check em. Thanks
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