Where can I get the rubber seal in the dome lid for the Vita Mix maxi 4000

this part is known as planetary and attachment hub, there are gears above this plate and oil from that area could be leaking past the planetary washer. you can see the details of this at the following link to the user manual. it is not clear if there is a seal behind the washer or if the washer itself is grooved with a rubber seal seated on the other side. removal would indicate wear and seal issue. but be aware that gears and other parts may come away if fully removed better to get someone to hold planetary together when removing the central bolt. if the maching has not been overhauled or service in a long time it maybe worth to this done to check all parts and seals for wear which may be cheaper in the long run.
https://www.alfaco.com/wp-content/uploads/2016/11/D300-Manual.pdf

I Hope this was helpful.

Turn off the water to the taps. Screw the top off your taps and clean off the rubber seals from lime or dirt and then put back together nice and tight. Hope that works

Ingredients:

• 1/2 cup vegetable oil
• 1/2 tbsp liquid dish washing soap

Directions:

1. Mix ingredients well in a lidded glass jar.
2. Add 1 1/2 teaspoons of the solution per each cup of water in the spray bottle and store remaining solution in the jar in the refrigerator.
3. Soak spray the infested plants and surrounding soil.
4. Repeat the rinsing and spraying for two more days and then use the solution thereafter once a week.
5. Do not spray when direct sun is on the plants because the combination of the sun rays and solution will burn the leaves.

The drip ring is held in place by friction. Simply put in place and tap it around with a small hammer (use a piece of wood between the ring)- and hammer).

I don't know what you mean by a "seal ring." The only piece I can thong of is a rubber o-ring around the agitator shaft (where you attach the beater). If it somehow broke and worked loose you will have to disassemble the machine to either replace the shaft assembly or to fit a new o-ring. The K5=-A service manual is available on line with a bit of searching.

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Did you ever find a replacement blade for your Maxi-4000? Thanks!

replacement can be found on amazon, take a look here: Amazon com Vitamix blade assembly. I hope this was helpful. Cheers

Get a copy of the Repair Part List for your model at Kitchenaid.com
Download a Copy of the Kitchenaid Service manual.

http://www.kitchenaidparts.be/centers/servicemanual/mixer.pdf

Somehow the O-Ring is coming off of the Vertical Center Shaft (11)
That rubber ring prevents Oil from the transmission gears dripping down
to the Planetary into your mix.

1. Remove the acorn nut, hex nut, and washer that hold the "planetary" agitator section on the transmission shaft.
2. Remove the trim ring (if any) around the same.
3. The agitator section should now be able to be worked free.
4. Remove the retainer clip on the top of the agitator shaft. (Some models have a pair of hex nuts here; if so, remove those.)
5. Pry the gear up and off the shaft. Remove the square key from the shaft keyway at the same time.
6. Tap gently on the top of the agitator shaft to drive it out from the bearings and grease seal.
7. Recommend removing and replacing the top bearing at this time; it's inexpensive to replace, if you're in this deep.
8. Use a suitable diameter piece of round steel stock to drive out the lower bearing and oil seal. I don't recommend using the agitator shaft.
9. Clean thoroughly, insert a new bottom bearing and oil seal, drive in place with a rubber mallet.
10. Replace agitator shaft through oil seal and bearing, tap gently into place.
11. Fill cavity with approved lubricant. I use USP-grade mineral oil, as it is food-safe and provides satisfactory lubricity.
11. Install top bearing, tap gently into place.
12. Reverse steps 5-1 to reassemble.

thats the planetary seal thats leaking.the seal is cheap its the labor that may be costly.is it just a nuisance leak or a lot?you dont want any oil to get in your mix.