In all of my senility, i managed to forget to put the gas cap back on and left the cover open when i finished filling up with diesel. It rained. It rains alot in Louisiana and it did yesterday. Other than changeing my fuel filters is there any thing else i might do. I forget, but does water settle to the bottom of diesel or does it float on top on mix right in with the diesel. thanks for your replies

Diesel floats on water. You may be able to search the forum and find out where the fuel pickup is. I suppose it would have to be close to the bottom of the tank. I would plan to drain the tank and get the water out of there. Maybe someone who has had experience will chip in some advice.

We'd be happy to share some of your rain -- it was 105 degrees and sunny here and more expected.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Pull your tank strainer and flush the tank with clean fuel, back flush the lines and add some of that "fuel drier". Your tank screen could proly use cleaning anyway.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

If the filler pipe was horizontal and facing upward, you would get about 5 oz. of water for every 1" of rainfall.

But, the pipe is nearly vertical and the area that faces upward is a fraction of the pipe size. So, my guess is that you've got no more than 1 oz. of water in the tank.........unless the rainfall was more than 1".

The water will be dispersed across the bottom of the tank and the chances of pulling the entire ounce at one point in time are virtually nil.

The secondary filter can handle the accumulation of one ounce of water.

However, I'd probably change it more frequently and look for water in the bottom to get an idea of how much is accumulating over time.

The other alternative is to drain the tank.........if you really want to be positive about the situation. Draining the lines is not required.

I believe the lowest point in the fuel tank is where the fuel is sucked from to go to the engine. If you disconnect the line that goes to your primary filter (the clear plastic one) and drain out fuel into a clear/glass container you can check for free water. Try a quart at a time into a mason jar or a gallon at a time if you have a gallon glass jug. The water should settle right to the bottom with the diesel floating on the top. If you are getting water in the samples give it a little time between drainings for the water to settle back by the suction again. Sometimes you drain it off faster than it can slide over from the other bottom parts of the tank. You may need to crack or remove the fuel cap so that the fuel will flow out easier. Between samples you can bend the fuel line over and clip it to stop the flow until you are ready to draw another sample. The fuel floating on top of the water is still good and can be reused.
Once you get nothing but diesel in the jar you should be in good shape. I would still add some fuel dryer every time you fill up for a couple of tanks just to be sure.
I forgot what kind of MB you have. My 87 has an aluminum head. Aluminum does not do well with methanol so I cannot use the yellow bottles of HEET to remove water. I have to use the red bottles of ISO-HEET. It is 92% pure iso-alcohol. I have no experience with the earlier engines.
-Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.

i would put in conditioner designed to combine with water and burn it out.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Don't know how much water got in there, my guess not much. Conditioner(alcohol) will take care of it.
On my tractor I loosen the fitting slowly, just until it seeps out of the threads. The water is on the bottom and is the first to seep out, and is clear if you let it sit overnight. As soon as you see fuel tighten the fitting.