There is no easy way. Many have tried and ultimately gave up, and bought a new or near-new tank (should be around $500?). If you don't fix the tank problem, you may ruin your fuel pump etc.
There is an alternative, and that is to (have a specialized shop) clean out, boil and re-coat the inside of the tank. Below is some information from our "technical articles" section (link:
http://sl113.org/articles/engine/fuel_delivery.asp) which is accessible to everyone (free members and full members alike). Please take some time to check it out, lots of good info on this and other topics there:
Joe Alexander said: "unfortunately some of the new fuel mixtures, especially those with
alcohol content, attack the original protective coating inside older fuel tanks. If you have an old Mercedes and you’re finding black flakes clogging your fuel filter and screens then this may be the case. When the original coating breaks down the tank is vulnerable to corrosion. Just flushing and cleaning the tank is only a temporary solution. The rust will usually return, especially in collector cars which spend much of their lives in not so perfect storage. The solution is to clean and re-coat the tank. A gas tank sealer was developed for the aviation industry where a pure fuel suppy is really critical. It is simply fantastic. I used it over the years on many cars, several 190 SLs with chronic rusty and flaking tanks. The cars, after twelve and fifteen years are still doing fine. The coating is alcohol resistant and forms a tough plastic coating impervious to any fuel blend. After cleaning the sealer is simply poured into the tank and sloshed around, the excess is poured out and the tank is left to air out for a couple of days. The resulting coating, besides protecting the tank from corrosion, also seals minor pin holes and leaky seams. Any rust or dirt particles left after cleaning become trapped in the tough coating and rendered harmless. To do a really good job, remove the tank, take it to a radiator shop and have it boiled out. If the tank is rusty inside, clean with acid, then coat with sealer. Order at least a quart of sealer so you can slosh it around good in those big Mercedes tanks. Use extreme caution when dealing with all that gasoline! Make sure you have enough gasoline containers available to store the gas when draining the system. A fire extinguisher should be kept handy. It might be best done outdoors if you’re doing it yourself. This sealer is available through numerous automotive distributors and aviation stores. The Eastwood co. is supplier to a lot of the old car people. You can probably find a better deal if you shop around. Try some aviation stores.
Will Samples replies: I may not be possible to pour gas tank liner/sealer in the tanks as used on W 113s due to the plastic basket that holds the fuel lines inside the tank. Anyone out there actually relined a W 113 gas tank and put it into service?
Joe: the plastic basket removes with the 22 mm drain plug. The next item to be concerned with is how to keep sealer from plugging the fuel lines in the tank. The lines go into a collector in the bottom of the tank where the fuel has no chance but to go through the plastic screen before going out of the tank on the way to the fuel pump. Possible solution: cut up a chemical-resistant rubber glove and wire one finger of the glove over the plastic screen, re-install the screen/drain plug. This should keep the sealer from clogging the screen and entering the fuel lines. Always check and clear the vent and fuel lines in the tank after using the sealer! One should also remove the fuel sender before sealing. I just use furnace tape to temporarily close off the filler opening, fuel lines and the opening where the sender goes. I like to take a flashlight and look inside during the process to make sure everything is covered. Before re-installing the tank, remember to clean the coarse screen on the intake side of the fuel pump. This can become clogged and most people do not know it is there. A W 107 series (450 SL etc.) in line fuel filter can be added as a second filter to the system as another line of defense against dirt and rust. It requires a little non-original cut and splice of rubber fuel lines. I wouldn't reccommend it unless you’re really having dirt problems. It will handle the pressure and the volume of a W 113 system just fine. My best advice is keep your tank full during winter storage, drive your car, use a good fuel from a newer gas station ( nice clean new fiberglass storage tanks in newer stations!)"
Cees
white 1969 280 SL
