Fixing a loose (noisy) impeller shaft

swamp-rat 2014-01-25, 03:36

Thought I'd share my process of fixing the impeller shaft on my XP4 today. I tend to be a bit on the innovative side, and when I realized what the problem was in the canister I drove down the street to McLendon's for a $3 fix rather than wait for a new shaft to arrive via mail or special order.

1) Identify the noise. In my case the noise was an intermittent rattling in the motor of my canister filter. PlanetRena.com suggested this was due to low water levels in the canister/air seepage, but as my canister was full within 1/4" of the top and no air was blowing out the discharge in tank I knew this was not the case. I opened the canister and removed the impeller cover and inspected the impeller assembly. All 3 fins were intact and although there were some slight grooves in the magnet of the impeller, they were not large enough to cause the noise I was hearing. However, I tested the stability of the impeller shaft that is supposed to keep the impeller in the center of the motor, and it was loose as seen in this pic:
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2) I removed the impeller shaft and identified that the rubber bearing on the end attached to the motor had shrunk after being empty and dry in my garage for 9 months. I needed a way to increase the diameter of this part to make a snug fit and prevent motion of the shaft. I brought it with me to McLendons, where I was able to fit 1/4" heat shrink tubing over the rubber with minimal excess. I considered an o-ring as the rubber appeared to have a notch for one, but decided that the o-ring would not provide stability evenly along the bearing piece and still allow motion. (see below)
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3) Once home and after 2 attempts at fitting the shrink-wrapped impeller in the motor I discovered the key to keeping the shrink tube in place on a slippery surface like this was to leave it slightly longer than the rubber at both ends so the shrink tubing wrapped around either end when shrunk.
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4) Cut the shrink tube to these guidelines, then heat with a lighter about 1" from the tubing, turning as if roasting a marshmallow until the tube has shrunk tightly around the bearing.
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5) Wiggle the shaft gently into place in the motor, making sure you don't force the tubing off thus negating everything you just did.
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6) One thing I hate about this impeller assembly is the lack of a tight hold at the other end of the shaft, in the impeller cover. Since I still had a little play in the shaft with the shink tubing in place I played extra safe and added the same type of bearing from a defunct impeller I had laying around and also shink wrapped that end to provide max support for the shaft. Now my filter is running like it did when I first bought it 6 years ago, quiet and efficient.

Of course, there are those of you that would rather skip this whole ordeal and just order a new impeller, which you can do at planetrenadirect.com