Well, it's been problem after problem with me lately in the crossfire. Friday night I was heading home and the car went into 'Prius mode' (supercharger shut down due to overheating due to auxiliary water pump failure). It was the knowledge that I've gained from reading this site that allowed me to instantly know what the problem was and to not panic.

Yesterday I did some testing and found that the pump was running, but not circulating any coolant. So I pulled it out, and being the tinkerer that I am, I decided to pull the pump apart to see why it would not circulate any coolant.

I first pulled the cover of the pump off and could see that the turbine was barely spinning when the pump was operating. I could put my finger on it to stop it from spinning completely, and a horrible grinding noise occurred. So I pulled the turbine off and the problem was obvious - there is a magnetic drum that is cast onto a gear that attaches to the motor shaft and there are magnets on the turbine shaft that allow the two to magnetically connect which rotates the turbine when the motor runs. Well, the magnetic drum looks to have shattered (I'm guessing it blew apart due to centrifugal forces).

Here are some pictures to show the problem area in these pumps. This first one shows the magnetic drum out of the pump:


Here's a 2 close up pics of the cracked magnetic drum, followed by a pic of the gear that it's cast onto:




Being the cheapskate....errr...ummm...frugal person that I am, I decided to play with this and see if I could come up with a band aid solution to give a little more life to this pump. I thought it was a shame that we junk these things all the time and the failures are all probably due to this one part failing. So I zip tied the drum back together onto the gear and tried it. Here's the rigged fix (note - I took this pic before I got it all lined up nice and put a second zip tie on for strength):


OK - so let's turn this thing on and see what happens:


As you can see - it spins! However, if you look closely you might be able to see that the centrifugal forces are too great and the zip ties stretched and the drum started to pull apart. I knew that with any load the gears would slip and the pump still wouldn't work. So I shut the pump off, and sure enough, you can see that there's no way this would hold together:


I don't know of anything that would bond the shattered magnet together with enough strength to survive the centrifugal forces so I called this part a goner and gave up on trying to repair it.

There is no part number on this drum(every other part on the assembly seems to have a number - just not this one...sweet....LOL). I searched the internet for a few hours last night trying to find replacement parts for bosch water pumps and came up empty. So I broke down and ordered the whole pump.

Not sure if this post will help anyone, but maybe it will find the eyes of someone who knows where to get replacement parts and can get us a lead on this part. It would be nice to not have to junk an entire assembly because of one small part.

Jon

 

Your testing is informative. The ferrite assembly is stretching the wire tie due to the LACK of load, i.e. water on the pump side. Without water to load the motor down, the rpms are up to an unusually high speed.

IF you were to repair the assembly Id suggest that you use slow hardening epoxy on the assembly and secure it BEFORE it hardens with a fine steel or stainless steel wire wound many turns and left in place. I have done this in the past but always was looking over my shoulder for the next failure.

The highest stress point that probably cracked it in the first place, was that toothed metal hub attachment point. THat is where the force is concentrated.

Woody, good photos.

 

Interesting idea on the epoxy with wrapped wire. Maybe I'll see if I can pick up a gear puller small enough to get the gear off the motor shaft and try that idea. There's definitely enough gap between the magnetic drum and the housing to allow the wire wrap to stay in place as a permanent part of the drum.

It would be even better if I could just buy that one part new

Jon

 

Very interesting jonnyb. Great pics. Thanks for sharing.

 

Wow, very interesting and informative. I am surprised that no one has torn one of these failed pumps down before. Thanks for sharing.

 

looks as if the drum is made of a cast metal....is that correct?

 

I think it is a magnetic material.

Great write up and photos to enlighten all of us.

James

 

Woody says it is ferrite in which case it would be sintered.

 

I was thinking it could be braized if cast...doubt that would work...so, I quess the heat and stress takes it's toll on this particular part...

 

I had taken mine apart and shown it long long ago. Ferrite is brittel and powered iron to form magnetic material. Woody