Bosch Dishwasher Repair – Drainage Problem Fixes

Bosch Dishwasher Drainage Problem Repair

Save the Cost of a Service Call with My Simple Guide

If you are having trouble with a Bosch Dishwasher that is not fully draining, not draining at all, or draining much longer than it should, you can do as I did -read all the forums, look at all the schematics, and take a guess at which solution is the right one for you- or you can read on and take my systematic approach that is sure to save you time and money. This is especially helpful if your dishwasher is emitting a hot, burning smell while trying to pump.

My Story – I’ll keep it short…

Bottom Line: I’m not an expert at anything, but I am a very handy guy (just ask my daughter!) who’s never been blessed with money. I fix everything I can to save money. I have fun doing this and while I would normally not work on an appliance of this cost and quality myself, I got a heck of a deal on the dishwasher and I could justify the expense of replacing a pump or whatnot if it came to it.

This dishwasher retails in the $800 range and is the best dishwasher I’ve ever owned, but I purchased it for $390 NEW! That’s a great dishwasher under $500 with extra to spare! It has served my family well until one day when my wife called to tell me our wonderful dishwasher had failed us

-Pumping for hours and emitting a hot, burning odor (although I thought it smelled more like a magic marker…). A little research had me calling the Bosch Dishwasher Helpline – 1-800-856-9226

– to replace the control board due to overheating and burning issues. Be sure to do this as well just to be sure you are not in possession of a defective unit.

To my dismay, the problem persisted even after the control board was replaced

I searched all the forums online for days with no good answer, just links to appliance part companies and a lot of “experts” telling me to buy a pump so I took out the toolbelt…

This is my experience. It may be different than yours, but I will walk you through it step by step so we can hopefully get your appliance up and pumping once again…

Let’s start, shall we?

Here’s a couple ground rules and a list of tools to get you started.

So your very expensive dishwasher is being unruly? Let’s get it back on it’s feet in less than a day, for less than a dollar. Here’s what you’ll need for tools: a Phillips Screwdriver (or whatever type you need to remove the screws holding the dishwasher into the cabinet), a T-25 Screwdriver, a Wet/Dry Vac and a Flashlight. That’s it.

I must insist that before the case is opened, you kill the power to the unit. There is a metal panel that acts as a ground on the side of the dishwasher that you may be removing to perform the needed repairs. There is no good reason to have the unit powered on while you service it. Remember: Work Smarter, not Dead…er….

By the way, I have photos coming soon. I wanted to get some whilst working on the unit, but the wife was getting frustrated and wanted this thing running ASAP!

Step One: The basics…

Water isn’t moving at one end of the line – Which is it???

The first thing we need to do is remove the microfilter from the bottom of the dishwasher. It is located inside the dishwasher in front of and underneath the wash arm. Check it for obstructions and clean it if necessary. Lift out the perforated metal floor grate of the dishwasher and clean it as well.

Now use a wet/dry vacuum to suck out all of the water you are able. Get right down into the bottom of the unit. If the water is clear, you should look first for any signs of a major clog here (glass shards, pieces of meat, anything unusual…). Water may back into the sump from the drain line. Continue to suck it out until it is empty.

Now use your T-25 to remove the screw holding the cover on the drain pump. Underneath the cover you will see the drain pump impeller. Look for any obstructions, glass or damage to the blades of the impeller. If you see an obstruction that is holding the impeller, clear it. If you see major damage to the impeller -STOP!- you need a major repair that I do not cover in this guide.

Just for kicks, run the dishwasher briefly with the cover on the drain pump impeller and the floor and micofilter removed. If the pump isn’t able to drain the dishwasher, and water streams out of the hole in the pump cover, we need to look at the other end of the line, beginning with the narrowest part of the drain line -The Air Gap.

Step 2: The Drain Line

A systematic approach to an interesting drain system…

I don’t know about you, but I installed my Bosch with an Air Gap. It seemed like a good idea at the time, but after just three years, it proved to be a major headache.

After taking a flashlight through the entire drain line and finding no obstructions, I decided to (YUCK!) blow into the drain line, only to find that it was insanely difficult to get any air through. This led me to the Air Gap, a small vent that basically serves the purpose of preventing siphoning through the drain line.

Before you remove the Air Gap from the sink, check to see if the cap lifts off or unscrews for servicing. This will save the time you might spend removing it from the sink like I did. Most are serviceable from the top of the unit. If yours is not, you may wish to just replace it with one that is.

Assuming you are able to remove the cover, do so and you should be able to see how to remove the top of the inner portion of the Air Gap. This is where the water passes through a small 180 degree elbow and then dumps into the drain line that flows to the sink drain or disposal, and this is likely where the plug will be. If not, you will need to unhook the drain line that comes from the dishwasher and drain it into a small bowl.

If you found and cleared a clog, reassemble the Air Gap and dishwasher and attempt to run a rinse and hold. If there is any remaining food in the drain it may re-clog, so be sure to watch it closely. Also be sure the dishwasher drains completely when finished.

Be absolutely sure there is no clog in the Air Gap or the drain line that flows to the sink drain or disposal before taking the next step.

Step 3: Inside the Unit

This step is really taking things a bit far for most people having drainage issues with their Bosch. I did these things to my unit before I found out the Air Gap was to blame. It is unlikely that this next step will do very much to solve the problem of water pooled in the bottom of the unit, but there is a good chance you need to do a little housekeeping here anyway. Before proceeding, you need to be sure that you have not found any clogs in the drain line from the back of the dishwasher to the Air Gap, within the Air Gap, or in the drain line from the Air Gap to the sink drain or disposal.

If you are sure there is no clog, switch off the breaker controlling the dishwasher and be sure to test the unit for power by pressing the “Power” button. There should be no lights or digital display illuminated on the unit.

Remove the two screws holding dishwasher into the cabinet. They are in the front of the unit, at the top. You will need to open the door to get access. Once removed, reach inside the wash tub and with both hands flat against the ceiling of the tub, lift slightly and pull the unit out of the opening, being careful to avoid scratching your floor. Depending on how your unit is wired and plumbed, you may or may not need to disconnect the water supply line and electrical service wire from the unit. I am not a plumber or electrician, so this is up to you to figure out. Mine was installed with lines that were plenty long to slide the unit in and out of the cabinet without the need to disconnect. I simply calculated my dishwasher’s dimensions before having it installed.

Facing the front of the dishwasher, you will notice a metal panel on the left side. Remove it using your T-25 screwdriver to take out the screws, and then slide it upward to release it. The drain system (actually called a water inlet system by Bosch) is located behind the panel, toward the rear and it has two large hoses in the bottom. One is from the drain pump and the other is the drain hose that goes to the Air Gap. The water level control system is located near the middle to the front of the unit.

Quickly make a visual inspection of the water level control assembly. Is it clean and free of deposits? Mine was not, so I cleaned it. It did help the unit fully drain after I solved the draining issue. You should be very careful to avoid damaging the parts and take a picture of your unit before disassembly for reference. This will aid in reassembly.

The nice thing about the drain system is that you are able to see right through it, as it is clear plastic. Start by making sure you do not see any blockage in the loop between the drain hose connections. Next, take your flashlight and shine it through the drain hose that goes to the drain pump (it is the shorter line, and it is under the wash tub. You may find it is easier to get the flashlight under the unit if the black metal toekick cover is removed from the front (at the bottom of the unit). This is where I wish I had had a portable dishwasher.

If no clogs are found, disconnect the drain lines from the bottom of the drain system (they simply pull out of the bottom of the water inlet system) and drain them into a bowl. If you removed the toekick cover, you may want to pull the drain line from the pump through the front of the washer where you can get the end of the hose lower and drain it better. Think this through, because there is not much room for a dish to catch the water here, maybe an inch or so. I used an 11″x13″ baking pan with 1″ tall sides.

Now we need to blow air into these lines. You may not want to use your mouth to do this, since this is dirty water and if the washer has not been used in some time, it could be full of bacteria and who knows what. Use your best discretion. Blow air into the long drain line first. Be sure your Air Gap is connected and that the Air Gap is connected to the drain as well. The air should flow unrestricted through the hose, and if it does you can be sure your drain line is free and clear to the Air Gap.

Blowing into the pump should be just as easy. If not, remove the microfilter, perforated tub floor and the cover from the drain pump. toward the rear of the unit in line with the impeller there is a hole that is approx 1/2″ diameter that leads into the short drain hose you just blew air into. Gently slide a flexible plastic drain cleaning tool into the hole and through the drain hose to clear any obstruction from the hose. Blow it out with air, and then replace the drain pump cover, perforated tub floor and the microfilter.

Once everything is cleared out and free of obstructions, we can reassemble the unit. Remember that the drain hose from the pump slides into the front port of the water inlet system, and that the drain hose flowing to the Air Gap slides into the rear port. Be sure the grounding wire is connected to the metal plate before you slide it onto the unit and remember to use both screws to reattach the panel to avoid noisy operation.

Step 4: Powering Up the Unit

Before we jump into this, let’s just go through our little checklist of things we disconnected and be sure that we have all of our connections tightened, wires connected, and tools accounted for. If you made other alterations, please check those as well. It’s never a good thing to have a pile of parts left over or to have left a tool inside the unit you are servicing.

Slide the unit into the cabinet and secure it with screws. If you do not screw it into place, it may fall over when the door is opened.

If everything checks out, turn on the breaker to the dishwasher and turn the unit on. Press the “Rinse and Hold” button (if equipped) or that of the shortest wash cycle. The drain pump will maybe run and then shut off a couple extra times at first and that seems normal once this repair is made. It should sound normal on the next run.

Be sure that while the unit is pumping, you are checking for leaks at all connections.

The first time I went through this process, I threw in a load of dishes and went to bed, only to find a very wet floor and counter in the morning. I thought I had a leak at first, but later found that when clearing the hoses, a bunch of debris that had been clogging the air gap washed into the drain line that flows to the sink drain and had clogged it as well. As a result, water backed up through the top of the air gap, over the counter and all over my (carpeted) kitchen floor. Save yourself the hassle and be sure to watch the unit the first time you perform a full wash cycle.