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    Gas Tank

    I just got another 325es. Car was parked for 3 year with a quarter tank worth of gas. Started up right away. What is the best way to empty the tank? Is there something I should do with the gas that is currently in it? Or should have to do the painstaking job of removing it by hand? I know I have to do the timing belt as well...

    #2
    A car parked for thee years with only a 1/4 tank full is undoubtedly well rusted.The tan is probably structurally sound, but the loose rust is quite abrasive and will eat up the high pressure pump quickly (not to mention clogging the filter). I've never found a way to clean the rust out without removing the tan.

    After removing the tank a quart or so of lacquer thinner sloshed around, the tank allowed to rest for ~30 minutes and sloshed again (rinse and repeat the lst two steps a couple more times) and then drain the lacquer thinner from the tank. Then I use is a simple wash with a strong TSP solution to remove an organics. I made up a simple plug for the hole where the in-tank pump mounts that could easily be removed. Think of a round disk of plywood with a bar on the bottom and a couple of screws to snug the bar up. Drop that into the opening, rotate slightly to engage the lock ears on the tank and tighten the screws. The remaining openings were closed up with pieces of a freezer bag held in place with rubber bands.

    About a gallon of diluted acid in the tank was about right. That was enough to slosh around well but not so much as too make the tank too heavy. I used an acid mix sold for cleaning masonry that's composed of Hydrochloric and Phosphoric acids at about double the normal dilution. Over the course of a couple of hours I'd slosh and flip tank every fifteen minutes to wet all parts of the tank with the solution. At the end of a couple of hours I drained the tank and disposed of the pretty well spent acid by reacting it with limestone gravel.

    To flush the tank I made up a right-angle spray nozzle with plumbing fittings and a 1/4" hose barb. That allowed the nozzle to be inserted into the tank and a high velocity stream sprayed into all corners. This was done with the tank at about a 30deg angle (drain plug hole down) and the fluid collected into a bucket. When the water ran clean and no more loose junk came out I repeated the acid treatment and flush. It took all of one Saturday and part of Sunday to get the tank to the point that no more rust could be seen and nothing was being flushed out of the tank.

    The last steps were to use the acid etch from an Eastwood fuel tank cleaning/sealing kit, flush with acetone, and apply the sealer. Before putting the sealer in the tank I removed the cross-over pipe and sealed those openings. And after the sealer had been applied and before it had a chance to harden I blew out those openings and the tubing that runs across the top of the tank with compressed air. After drying for a couple of days the tank was reassembled and reinstalled in the car.

    Once sealed the inside of the tank had a fairly uniform white coating. I did see a few specks of matter that I wasn't able to flush from the tank, but those were well locked in place by the sealer.

    Cleaning and sealing the tank is pretty labor intensive. But at a total cost of less than $80 it is a lot cheaper than a new tank (~$400 for an 87 model or earlier).
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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