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sudsmaster

sudsmaster

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Dec 23, 2004
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SF Bay Area, California
Overall, I love my Bosch SHU43C dishwasher. Although I have a collection of vintage KA/Hobart dishwashers, the Bosch continues to amaze me with how quiet and efficient it is. Plus I love being able to load plastic items in the lower rack; the water heater is inline with the circulation pump so there is no need to have an exposed heating element near the rack.

However, for the past half year the Bosch has been making these strange moaning/groaning noises on some (but not all) drains. It still works, it's just not whisper quiet any more.

Thanks to the magic of the internet, it just took a few google attempts to diagnose the weird sounds and find a cure.

Apparently the plastic housing for the drain pump impeller tends, eventually to wear a bit large, which allows the impeller to thrash around some, creating the noise. The good news is that the pump can make this noise for a long time before it actually fails. Even better is that the pump is serviceable from the front of the machine - no need to uninstall the DW to replace the pump. Since a new pump is about $86 with shipping, I have one on order from Repair Clinic as I type.

And if all else fails, I have a choice of vintage KA/Hobart DW's to stick in the Bosch's coveted kitchen nook (The KDS-18 probably the front runner).
 
Good Design

There is something to be said for the Bosch dishwasher design. Simple to install and simple to service. Kudos to Bosch on that one. If you can handle the drying aspects, it is an easy machine to live with...

Malcolm
 
You can access the impeller directly

Yep, already did that procedure, there is nothing blocking the impeller. It drains ok, it's just noisy. And from what I gather, it's because the bearing surface(s) that impeller shaft rides on are worn (or the impeller shaft itself) and it wobbles excessively as it turns, causing the noise. The suggested cure is a new drain pump. Which is on order.
 
If you can handle the drying aspects

I run the machine on the hottest and longest cycle, and don't have a problem with the way it dries. Yes, it does leave water in the bases of upturned cups etc, but that is easily removed with a swipe of a dish towel, and IMHO preferable to a hard to remove layer of dried out water minerals. Anything that doesn't collect water by gravity dries adequately for immediate storage once the cycle is done.

Of course, like all such DW's, the cycle time is quite long: 109 minutes, nearly two hours, so some planning is needed if one needs clean dishes for a meal service etc. In a pinch I could fire up one of the two top loading KA/Hobart dishwashers in the patio kitchen, but generally that is not needed. Eventually I'm planning on moving one of them into the main kitchen so it's more convenient to access. It has a butcher block top so it could function as temporary storage/prep space which is always welcome.
 
Well the replacement $90 drain pump arrived yesterday. Today I installed it. Was it an ordeal? Of course!

Bruised knuckles and blue verbs later, I was able to extract the old pump. When I went to hook up the new one, I saw an immediate problem: the wiring terminals were different. Instead of being able to accept separate load and neutral wires, isolated with a wall of plastic, the new pump had the terminals close together, inviting a short. A visit back to the web sites dealing with this problem revealed there's an adapter cable needed to hook the replacement pump up to these older machines. Only one problem: the adapter cable is not in stock and would take up to three weeks to arrive.

I rummaged around in my big box of electrical connectors, and realized there was a simple enough work around. First I got out the shrink tubing and heat gun and insulated the female spade connectors at the end of the existing wires. Then I cut a length of 1/16" thick polypropylene sheeting (which I just happen to have handy). I installed the shrink wrapped wiring on the new part, then eased the plastic separator between them. Instant electrical isolation.

Eventually I got it all back together, and tried a brief "quick wash" followed by a manual drain. No problem. No sparks. And no squealing from the drain pump. Haven't had a chance yet to run a full cycle, but I'm expecting the noise is gone for good. Time will tell!
 
Hey, you fixed it!

99% of the population today probably couldn't do that.

Now you have plenty of time to watch the Steelers send the Chiefs to a 1 and 8 record...or some better use of your time.
 
Here's the explanation of the drain pump noise, and the basic process for replacing it on this particular machine (SHU43C):

The way the pump works noisy is because the motor magnetically drives a metal stem inside of a plastic housing and on the end of the stem is the propeller blades that drive the water out. Over time the plastic housing will expand a little bit giving room for stem to vibrate more than usual. It's ok to run it until it quits, The worst that would happen is it just wouldn't drain and would fault out until the pump was replaced. There are 2 separate pumps on this machine. A circulation pump and a drain pump. The drain pump is the one you will need sometime. To replace the drain pump you'll need to remove the toe kick panel under the door, the insulation (if Applicable ), Metal piece above insulation with one T15 torx screw at each end and the pump will be in front of you. To remove the pump simply pull the clear hose in front of it hooked to the sump and move it aside. Squeeze the clip and turn the whole pump away from you. It should pop out and in easy so take your time at this point. pull the two wires from the old pump and place them back on the new in the same order ( Be sure to turn off power at panel box ). Other than that you should be in good shape:) Let me know if theres anything else I can help you with.

Read more: 2nd try-here goes. Bosch dishwasher pump making a loud droning - JustAnswer http://www.justanswer.com/appliance...r-pump-making-loud-droning.html#ixzz2BwyGoPZT

My note: It omits the need to have plenty of towels if you already haven't sopped the water out of the sump. Probably one would need the towels anyway. The drain hose is a friction fit with a black rubber o-ring, so you just pull it out of the sump port. The toe kick panel has to be removed with two screws, and then the Z-shaped piece of metal (big) that fits up into the door. This part gave me some trouble because it was either stuck by food residue or glue. But eventually it came out. The above process seems to be in error: you have to turn the drain pump towards the front (clockwise looking at the back of the pump), not "away from you". More water comes out when it's removed. Have more towels. Putting the new one back in was a bit tricky - it's hard to see what's going on, but eventually it slides in pretty easily. I note that the replacement pump has 9 vanes, which are beveled, while the original one has only about six vanes, which are square. The original is also 33 watts, while the replacement is 44 watts. The replacement sounds slightly louder than the original in normal operation, but that might be because I had the kick panel removed when I tested it. I did run a full cycle and didn't notice any more squealing, moaning, groaning noises coming from the dishwasher. So I think this repair will give the machine another 10 years or so.

 

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