One of the few non working items on my 99 U320 was the toilet. It wouldn't hold water. I tried all the simple fixes with no luck.
I pulled it out and ordered parts. It wasn't that hard because the parts came with really good instructions. Figured I would post the part numbers and pictures of the 3 part package instructions.
The toilet had about 1/8" layer of mineral deposits that were not letting it seal. I went ahead and did the ball and the bottom gasket. Whatever gasket that was there, wasn't anymore. Glad I pulled it out all the way.
Items
2 PART BOWL SEALS WITHOUT DRAIN HOLES 311462 (REPLACES 310677)
1 × 2 PART BOWL SEALS WITHOUT DRAIN HOLES 311462 (REPLACES 310677)
$35.95
This Kit can be used with any foot operated toilet that has a medal flush pedal
covered by a plastic pedal cover.
1 × BALL, SHAFT AND CARTRIDGE KIT 318162
$45.95
This floor flange kit contains the floor flange seal and hardware.
1 × KIT,FLOOR FLANGE SEAL ( 385310063 )
$23.60
You might want to keep you an extra spring cartridge. I'm on the 3rd one in 4 years. I use a little CLR and let it sit a bit then and old tooth brush, then a little plumbers grease about twice a year. That seams to keep the deposits from building up on the flush ball and seal.
Mine fell apart as I took it out. Probably have to buy another one at some point.