Bosch SHU99 Dishwasher With a Mystery Leak Underneath, Somewhere on the Right-Hand Side, Making the Pump Run Constantly

by Samurai Appliance Repair Man on September 1, 2010

in Dishwasher Repair

If you’re struggling with a mystery leak from you Bosch dishwasher and you can’t see from whence the leak doth originateth in accordance with the 7th Law of the Prophecy, then this harrowing tale from an intrepid Apprentice in the Samurai Appliance Repair Forums, Chesterfoxes, probably holds the answer. This particular war story was from a battle with a Bosch model SHU9915UC/U11 but the wisdom contained herein applies to all Bosch models from that era such as SHU43, SHU53, SHU68, SHI43, SHI53, SHI68, SHV43, SHV48, SHU33, and SHU99.

First and foremost, thanks for all the tips and hints from everyone – they were very helpful in getting this done.

Second, BLESSED IS THE MAN OR WOMAN WHO SERVICE THESE MACHINES, FOR THEY SHALL HAVE GERMAN ENGINEERS FOR SERVANTS WHEN THEY GET TO HEAVEN!

To anyone who has stumbled upon this post in an effort to solve their Bosch leak, I’ll give you what I’ve learned.  Bear in mind that you’re machine is running onward forever as there is a float switch in the base that has been tripped (by leaking water) and thus puts the drain motor into continual operation.

1.  Before doing anything (other then soak up the water in the base), remove the outer door shell and the panel at the bottom of the door – this will open up your field of view into the base.  The outer door shell comes off when you remove the four screws on each side of the inside door rim.  Then run the unit and see if you can visualize the leak.

2.  If it’s the drain pump that leaks (or the water valve), you’re in luck because you can probably change it out without dropping out the base.  If it’s one of the other gaskets (pump to sump or pump to heater) you’re basically screwed and are in for a long day.  This is because you’ll have to drop the base to get to those components.

3.  If you need to drop out the base, then first disconnect the unit from power and water and pull it out.  Take out the drawers.  Next, remove both side panels – held on by two screws in each side on the front vertical trim pieces on the front tub rim.

4.  Remove the two screws in the back that hold the bottom tub onto the frame.

5.  Lay the unit on it’s back.  Remove the door springs from the base.  Disconnect the ropes from the springs.  Remove the screws in the front of the unit holding on the base.  Take a few pictures of how the wiring is routed around the base.  Unscrew the water valve and the electrical j-box from the base.  Then pull the base off.

6.  On my unit, both the pump to sump and pump to heater gaskets were damaged and leaking.  This was probably due to the unit being laid on it’s side or upside down during shipping/installation (seven years ago) and one or both of the rubber motor suspenders became disconnected from their connecting posts on the base.  This left the motor weight being either partly or entirely supported by the gaskets and likely led to their premature failure.

7.  Oh yeah, great German design means that the pump to heater gasket is integral to the heater and you’re on the hook for an entire new heater.  On the plus side, you get a new heater element, NTC, thermistor and flow sensor with the new assembly.  You’ll need to order a new hose clamp for the gasket between the heater and the pump. 

8.  I rebuilt the pump with the kit that includes a new pump housing gasket and pump impeller.  Impeller unscrews from the motor shaft – use a screwdriver jammed into the metal fan/cooling fins (at the other end of the motor) to stop the motor from spinning while you unscrew the impeller.  Don’t be an idiot and nick the motor windings.

9.  Install new door gaskets while you’re at it – not a big cost.  My main door gasket was becoming gelantinous at the bottom corners.  The bottom door gasket had a 1/4-inch of thick goo and two splits – definitely should be on anyone’s list while the machine is apart.  The main door gasket just pulls out of its slot – jam the new one back in the slot.  The bottom door gasket is a bit tricky – the end brackets for the seal are sandwiched between the door and the hinges.  Only remove the lower of the two hinge screws – remove both and the door becomes uncontrollable.  If you put the new bottom seal next the the old one (before you remove it) you’ll have a good idea of how to approach it.

10.  Once I installed the new pump to sump gasket, the new heater assemply, and re-built pump, I suspended the motor from a piece of wood spanning the front of the machine until I got the base re-installed – it’s a lot of weight to be hanging on the sump and heater.

11.  Don’t remove the sump from the tube unless you have to (see a leak?) – it’s a pain in the balls to get back in correctly.

12.  Slide the base back onto the unit – don’t forget the rubber support that goes between the center of the sump and the base.  Key item – get the rubber motor supports hooked back onto the two posts in the base.

13.  There is a lot of work involved in putting the base back on – first, check to make sure the condensate drain pipe is routed throught the correct hole in the base.  Second, make sure the water fill and drain apparatus (on the left side of the machine) is correctly together and in the right location.  Next, make sure all the wiring is correctly routed – put the wiring connection blocks back into their holders on the base. 

14.  Before tilting the machine back up, re-install the door springs.  This is a pain because without the springs, when you open the door the plastic connectors (at the opposite end of the ropes) likely came out of where they should be on the hinges.  Also, the white plastic covers next to the hinges probably became dislodged.  Check all this before hooking the ropes back up to the springs and re-installing them.  Re-install the two front screws holding on the base to the frame.  Tilt ‘er up!

15.  Once you’ve tilted the machine back up, get back on you’re belly.  First, make sure the rubber motor suspenders are hooked to the posts on the base.  This is key.  Then, check all the wiring routing to make sure it’s off the bottom of the base and also not laying on the water heater terminals.  Check the water fill and drain mechanism (on the side of the machine) to make sure it’s seated in the correct position on the base and that they’re back together they way the started the day.  Re-install the float and rod.  Screw the water fill valve and j-box back into the basee.  Re-install the two screws in the back of the machine to secure the base to the frame.  Once you’re satisified all is good in the base, re-install the side panels.

16.  Re-install the machine and run it.  Make sure (visually) the leaks are gone and everything is good.  Then reinstall the plate at the bottom of the door and the outer door panel.  Find the kick plate (taken off weeks ago when it first started leaking) and put it back on.

All told, I replaced the two door gaskets, the drain pump, the heater, the pump to sump gasket, and re-built the pump.  About $230 in parts.  Never having done this before, it was a chore to figure it all out.  It was probably a coin toss whether to fix the unit or replace it, but I’d probably rather fix it then throw it in a landfill.  I put in enought parts that – knock on wood – it should be good for another seven years.  However, if I had to pay someone to do this (no matter how good they were) I doubt that I could justify not going out and buying a new one.

Overall, the design is fairly slick – the bottom tub and flood sensor has probably saved the day more than a few times.  It’s just awfully difficult to slide the base back on while making sure everything is back where it should be – I felt like I needed two more arms and hyperflex elbows.

A final thought – if only the pump to sump gasket is leaking, I’m not sure how you disassemble the unit to replace it without also getting into the heater to pump gasket.  Is it possible to pull the pump out of the sump (to replace the pump to sump gasket) without pulling the pump off of the heater assembly?  Probably not.  Only problem is that the pump is held onto heater assembly gasket using a crimped-on hose clamp.  How do you temporarily separate the pump from the heater assembly?  I guess you could be clever enough to loosen the crimped on hose clamp.  Maybe there is enough flex in the heater to pump gasket to allow you to pull the pump off of the sump.

A second final thought – why are the door gaskets (and others) turning waxy/greasy?  I use regular diswasher detergent, no rinse aid, have a water neutralizer (not softener).  Too much heat?

Hope this helps someone else – either to do it or to decide to call someone else to do it.

Can I hear an “A-freakin-men?”

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