Well you should definately consider a fluid change and full brake bleeding.

I suspect you may have air in the system.

In any vehicle, if I ever had spongy brakes, it was due to air in the system.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon - Sold
2006 E350 Wagon - 368 - Dead
2015 GL350 Bluetec - 197U