Though it is not the same model this might help others...
On my W126 I had the same problem but a little more severe. My pumps were rusted through due to the rotting of the rubber gaskets. Both pumps were in need of replacement, $37 later I removed the hoses, washer fluid level checker disconnected and pulled out the tank. Quite an easy job though I had blockage in my lines to the nozzles, headlights and windshield. Used an air tank to blow out the lines. Couldn't be happier, it was my first DIY'er for me.
And Keep On Driving!!!
1987 560SEL SOLD@216K