240D algae part 6 – How I ruined my W123 fuel tank

In the last part, I used a fuel tank sealing product to seal my W123 fuel tank.   This seemed to go quite well, but it turns out I had made a fatal mistake.   Once I had coated the inside of the tank, I very carefully cleaned the openings for the sender unit and strainer.  I made sure the threads were clear of any sealant.   However, I forgot to remove the pipe cleaner I had used to block the return line.

When I returned 24 hours later I realized my mistake.   It would have been a second to pull it out the day before but even after 24 hours it was stuck.    Try as I might, I was not able to pull it out, even putting my feet against the tank and pulling back with all my weight.

A couple of days later I came back with a new plan.  Instead of pulling it out, I would push it through.    I hammered through a couple of thin drill bit.  I thought this might break the bristles off the walls of the tube, allowing the pipe cleaner to be pulled or pushed through.

It wasn’t to be.  After using a slightly bigger one, it managed to break off.  I then used a punch to try and hammer it through, but the tank was so well sealed it just went through the walls of the return line.

While it is probably possible to cut out this part of the tank and weld a new section, I don’t have the skills for that.   So I am now on the lookout for another W123 diesel fuel tank.   It’s a shame, as other than rust at the bottom this one was in reasonable shape, and it looks like it was an 80 liter tank from a later 300D.

It is rather annoying as the car is going to be off the road for far longer and I am up for the cost of another tank.  However, mistakes like this are going to happen from time to time when you take on jobs like this yourself instead of taking to a professional.   This is is why I try to take on things that the ramifications of a mistake are fairly correctable.  For example in this case a 2nd hand tank vs an engine rebuild.

I don’t regret trying to seal the tank, my mistake was not making sure all three openings were clear.