KitchenAid 21 and 22 seal replacement

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The KDS-21 I bought had a leak seal. Even after letting it sit for an hour with hot water, the seal still leaked. So, it's time for replacement.

At the same time while it's apart, we will look at how this pump works, and what it's future contribution is to the Whirlpool PowerClean pump.

 

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The first thing we will do is remove the hydro sweep spray arm and the medium filter.

KitchenAid changed the pump design for the 21 series, and at the time the only manufacturer who offered fine particulate filtering was Maytag with the reverse rack. Fine filtering is great for removing particulate that is lighter than water. In the 21 and 22 series pumps, a small portion of the flow is diverted from the wash to be finely filtered and returned to the suction of the wash pump.

 

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There are four main screws that hold the filtering chamber to the pumping chamber, and that will expose the wash impeller.

 

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Remove the suction base for the wash impeller by the five screws that hold it on. We have to be careful here as the coarse filter catches things like broken glass and old paperclips, you don't want to cut your finger.

 

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Remove the drain pump seal and cover. The seal will be replaced anyways, so if it gets destroyed its okay.

 

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The drain impeller can be hard to get a grip on as its sharp, so I used a few hook tools to carefully pull it up. This impeller comes in the seal kit as it contains the other half, the carbon half, of the mechanical seal. Do not reuse this impeller, just throw it out.

 

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The old seal and spacing rings need to be removed from the motor shaft and pump base. The ceramic seal is surrounded by rubber that fits in the pump base, so a small flat blade screw driver can fit in this space, but be really careful to not damage either the shaft or the pump base.

In photo one you can see the old seal (with the wear on it), and the spacing rings.

Photo two shows the new seal and new spacers that come in the kit.

 

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This is where the seal replacement will split the boys from the men. By far, this may be the hardest or most tedious replacement because of this one thing.

Because the motor height can vary from machine to machine, spacers are required to make sure the mechanical seal sits properly and wont wear too fast, or seal improperly. The drain impeller will sit on top of the spacing rings. The kit includes two thick rings, two thin rings, one final ring, and a rude feeler gauge to check the spacing.

First, take the feeler gauge and look at both ends, one has T written on one end and the other has C. with the T end touching the bottom of the pump base where the seal sits, use this to get an idea of how this will work. The feeler gauge should just clear the lip on the motor shaft. Now, take one of the thick rings and slip it over the shaft. Check the height using the T end of the feeler gauge. If the gauge JUST touches the top of the seal, youre good. If it doesnt and there still is minimal clearance, add another thick or thin seal until the feeler gauge JUST touches the rings. Once it does, there is a final ring that is taped to the instructions that you will slip on top of the shaft. Now, flip the feeler gauge around so the C side is in the seal housing for the pump base. The C side of the feeler should clear the sealing rings perfectly. The height is now set.

 

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Hold the new drain impeller with four fingers and slip it over the shaft and push down EVENLY (hence the four fingers) until the ceramic side bottoms out on the carbon side. You should be able to push down a bit on the impeller and feel the spring that holds the seal faces together.

NOW for how this works. Remember how some impellers will still pump even if they run in reverse? And how WP and Maytag took advantage of this to backwash their filtering chambers? WELL, in order for wash water to enter the drain impellers suction, it has to pass through the coarse filter first. When the machine is in wash mode, a small portion of the wash water enters the suction of the drain impeller and is pumped through the channel that the screw driver is pointing at.

Most of the wash water will go through the medium filter and into the wash impellers suction. Essentially whats happening here is that the wash water is split 75% to the suction of the wash impeller and 25% to the drain impeller.

 

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There is a new drain cover gasket that needs to be fitted on the pump base first, then the drain impeller cover can be screwed back on. Next, screw the wash impeller suction base back on with the five screws.

See this port here? This port mates up with the channel the screw driver was pointing at. It is the entrance to the fine filtering chamber. So, at this point, a small portion of wash water is filtered through the coarse filter and then pushed up by the drain impeller in to the fine filtering chamber.

 

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Fit the bottom half of the pumping chamber to the suction base of the wash impeller. A medium sized o ring, included in the kit, needs to be fitted in the drain impellers upper cavity. The impeller itself can now be put on the motor shaft. To secure the impeller, the screw holding it needs to have a certain order. It needs to be screw, washer, lock washer, keyed washer, and small o ring. Fit all of these on the screw and use the new o ring included in the kit. The o ring will hold all of this together, and then you can screw the impeller to the motor shaft.

At this point in the washing system, wash water drawn through the medium filter is pulled in to the wash impeller and is to be distributed to the hydrosweep arm and the upper rack arm. A VERY small portion of wash water is diverted to the underside of the hydrosweep arm to self clean it, and also the suction base in a small attempt to back wash the medium filter, as highlighted by where the screw driver is pointing.

 

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You can now reassemble the top portion of the pumping chamber to the bottom portion. And the seal replacement is done! Kinda, you have to obviously put the coarse filter and medium filter back in place, and then put the hydrosweep arm back on and test it.

See this solid piece I'm pointing at? That port we looked at that comes from the drain impeller pumps to here, its a distributer plate which will push water around the fine filtering chamber. Water now must pass through the fine filter to get to the suction of the wash impeller.

 

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The fine filter, micromesh, would clog quite fast. So, just like Maytag, KitchenAid has a continuous backwash thats provided by a small portion of flow from the hydrosweep arm. And because the wash impeller will still pump when running in reverse, these ports will also help push the collected crud down the drain when its time to... drain.

 

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The now finely filtered water flows out and is found in-between the medium filter and the suction of the wash impeller.

The upside of this style of filtering is that, at the time, the only other brand that could create water as clean was Maytag. Fine filtering can remove particulate that is lighter than water which is something that the centrifugal seperation in the Whirlpool PowerClean cannot do.

The downside is, well, only a small portion of flow is diverted to the fine filter. So the rate at which fine filtering happens is slower than Maytag or any other brand.

 

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When Whirlpool bought KitchenAid, they also bought the intellectual rights to their designs. And in 1991, Whirlpool filed a patent for a revision to the PowerClean.

Instead of having a pressurized soil chamber where water had to "float" to the exit in the PowerClean, Whirlpool decided to have the top of the soil chamber open by placing fine mesh over it. Thus, when wash water was diverted to the centrifugal separator, when it made its way to the soil chamber it passed through a fine mesh filter and back out to the pumps sump, much like this design that KitchenAid came up with. The fine mesh is backwashed just like the KitchenAid 21 and 22s do it, by a jet hole in the bottom of the spray arm. This, is the final revision of the PowerClean. WIthout the 21 series pumps, there is no advanced PowerClean.

Essentially what happened was Whirlpool took the best of the PowerCleans ability, which was the high rate it can filter water, and the best of the 21 series pumps, which was the ability to filter particulate lighter than water, and morphed them in to one powerful, all mighty pump. Were looking at the genesis to the PowerCleans revision by looking at KitchenAId.

Of course, a trial run is necessary to make sure your seal replacement went off without a hitch...

 

[114jwh]

Great job Kevin!

This is a great how-to for anyone needing to do some remedial work on a KA 21. Your attention to detail is pretty amazing!

I do have a set of racks and various parts from a KDSM21 I salvaged several years ago. If you want or need them they are yours for whatever shipping is.

Once again, thanks for the write up and great job!

Happy New Years too!

 

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Thanks James!

I'm OK for racks right now, but if I need any I now know where to look! Thank you!

Happy new years everyone!

 

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Many thanks for this potatochips.