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  #1  
Old 12-30-2005, 02:09 PM
d.delano's Avatar
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Aux water pump replacement

All-
I have to replace my aux water pump. It's drawing too much amperage and already fried my CCU. I have four questions:
1) How difficult is this R&R?
2) I haven't looked to see where the pump is located. Where is it?
3) Will I have to drain the coolant for this procedure?
4) I need to procure a fuse holder and fuse to prevent CCU from burning up again in the future. Where can I get these?

Scored a used CCU already & still have two old ones which are both fried. May try to make 1 good one out of the 2 bad ones. Thanks all.
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  #2  
Old 12-30-2005, 02:16 PM
Craig
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How do you know the pump is the problem if you haven't even looked at it yet? It's located in the heater hose that runs from the monovalve to the front of the engine, right front, just a little above/behind the alternator.
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  #3  
Old 12-30-2005, 02:17 PM
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Topic has been covered many times

Do a search, eh?
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  #4  
Old 12-30-2005, 04:54 PM
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Quote:
Originally Posted by Tirebiter
Do a search, eh?
Sorry guys, been there done that- got 17 threads, none particularly useful for the questions I posted. If you have some advice for some better keywords than 'aux pump replacement' then I would gladly accept it. I asked out of last resort. I think it's funny that I get my ass kicked asking a question like this but somebody that ought to know to not start another oil thread can come on here asking about what oil to use or somebody else can ask where to buy valve adjustment wrenches for the 3,000th time and you go all out to help him, and end it with a very nice 'help is what we do here have a nice day'.

"How do you know the pump is the problem if you haven't even looked at it yet?"

I am speculating. I am speculating because I ran a search and all roads lead to 'bad aux pump'; none of the threads that I read offered any other cause. I have ALL the classic symptoms, hence my reasoning for jumping to the conclusion I have. I would be glad to peruse whatever thread leads you to believe that there are alternate causes, because believe me I don't want to buy a new pump @ $180. I do thank you Craig for pointing out where the pump is located. So my CCU is fried, suffering the same exact damage as the one before it. What do you think the cause is? Bad aux pump pulling more than 1.3A? I think it's a safe bet, considering the thing's 20 years old, and I really don't have the time for a lengthy diagnostic, nor do I have the equipment. I have what it takes to solder in a fuse holder and R&R the pump(if I don't have to drain the coolant that is) and CCU but beyond that my capabilities are limited here in NW DC. By the way I'm pre-thinking about this repair, and haven't decided the details of the execution. So I still have the latitude to come to another, cheaper, and more prudent solution if I can get some knowledge somewhere, which I am trying to do. Only solution I have come to is bad aux pump, simple as that.

Look- I realize ganging up on folks on the internet is fun and all but I didn't ask for this. I am truly very sorry for invoking your ire, but I'm beginning to feel persecuted here on the forum. Every thread I start, furthermore all of my posts, are met with an abrasive response. I do my best you know, I have tried to help others and basically my help is ignored and someone can come on and say the same thing and get praised for helping the helpee, I buy my parts from FASTLANE, I say please and thank you; what do I stink or something, you been talking to my ex-girlfriends, what?

Again, fellas- my apologies. Really. The reputation that the shop forum has for being contentious isn't the least bit deserved, and I promise this is the last time you will have to field any more of my ridiculous time-wasting questions as my dumb ass won't be posting here any longer. Happy New Year!
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  #5  
Old 12-30-2005, 05:18 PM
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Replacing the Auxiliary Water Pump on the W126 1985 300SD

Replacing the Auxiliary Water Pump
on the W126 1985 300SD
by whunter
http://www.peachparts.com/Wikka/W126AuxPump
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  #6  
Old 12-30-2005, 05:22 PM
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your questions are welcome any time, ignore the negativity/rant over nothing type of stuff, some people need/like to dump you know.
The motor in the aux pumps normally draws about 1.5 or 2 amps and when they fail they draw tens of amps and the circuit traces on the CCU melt. I have a bunch of motors in that condition. I actually am using a CCU that I patched by using small dia buss wire to solder across the gaps left where the copper vaporized. Its an ugly fix but works if that is all that is fried. Be aware however that there are some tiny relays that can fail on the CCU and the best solution is to either send the module to be rebuilt or find a good used one.
The fuse holder can be found at a PEP boys or similar or an electrical supply, maybe Radio Shack if they are well stocked (most are not these days!)
A regular 5 A (non-Slow Blow!) fuse should be about right I believe. It doesn't matter if you use a glass cartridge fuse or the newer ATC type used in automotive applications.
As for repairing the motors, let me know if your successful and I'll send you a few to repair, I believe they are pretty well sealed up and replacement brushes will be hard to find, Bosch made them with no easy repair possible (they obviously sell a lot of them) A rebuilt 1238301285R runs $163.
Also, I've used pumps from 126 and 124 models for the 123. They work fine. To do that you have to remove them and put them on the rubber mount on your vehicle. Using a thin blade screwdriver, spray WD40 under the rubber and twist the motor around till its free.
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Last edited by dieseldiehard; 12-30-2005 at 05:27 PM.
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  #7  
Old 12-30-2005, 05:43 PM
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Quote:
Originally Posted by d.delano
Look- I realize ganging up on folks on the internet is fun and all but I didn't ask for this. I am truly very sorry for invoking your ire, but I'm beginning to feel persecuted here on the forum. Every thread I start, furthermore all of my posts, are met with an abrasive response. I do my best you know, I have tried to help others and basically my help is ignored and someone can come on and say the same thing and get praised for helping the helpee, I buy my parts from FASTLANE, I say please and thank you; what do I stink or something, you been talking to my ex-girlfriends, what?

Again, fellas- my apologies. Really. The reputation that the shop forum has for being contentious isn't the least bit deserved, and I promise this is the last time you will have to field any more of my ridiculous time-wasting questions as my dumb ass won't be posting here any longer. Happy New Year!
There is nothing personal in their comments.

I hope the link I posted helps you.
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  #8  
Old 12-30-2005, 06:10 PM
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I apoligize for "Tirebiting" you.

The easiest way I have found for checking the aux pump is to use a couple of jumper wires directly to the battery. Disconnect the pump electrical lead and hook up the neg jumper. Scratch the positive jumper to the positive battery post. BIG time sparks or a pump that doesn't run means it's time for another pump.

PLEASE don't forget to place a one amp fuse inline.
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  #9  
Old 12-30-2005, 06:13 PM
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Quote:
Originally Posted by d.delano
2) I haven't looked to see where the pump is located. Where is it?
See the attached picture. I expect that yours is similar.
Attached Thumbnails
Aux water pump replacement-aux_water_pump.jpg  
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  #10  
Old 12-30-2005, 06:24 PM
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Quote:
Originally Posted by d.delano
...... as my dumb ass won't be posting here any longer. Happy New Year!
Watch your language!!














I'm Kidding!

Actually, in my opinion you did exactly as we all should. Research the issue, ask any more questions if necessary. You had the price already, which demonstrates more preperation. So don't sweat the knuckleheads that bust on you. You can tell which ones are just trying for some good natured knad-busting.
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Last edited by JimmyL; 12-30-2005 at 11:34 PM.
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  #11  
Old 12-30-2005, 06:45 PM
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Excellent. Thanks to all. To recap, I shall-

1) Put a 1A inline fuse in the replacement pump, pos wire
2) clamp off the two heater hoses
3) pull the old pump
4) install new pump
5) pull old fried CCU that I had just fixed(DOH!!!)
6) install new 'used' one that I just got, hope it ain't fried (ain't seen it yet but my nose knows)

Will there be anything special that I have to do i.e. 'burp' the coolant system or something to get the air out that I introduced with the installation of the new pump? I'm going to do this without draining the coolant as I just replaced it and just don't want to replace it again.

You all know I drive an MB diesel so I can't do a fool thing like never post here again
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  #12  
Old 12-30-2005, 07:48 PM
Craig
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Quote:
Originally Posted by Craig
How do you know the pump is the problem if you haven't even looked at it yet? It's located in the heater hose that runs from the monovalve to the front of the engine, right front, just a little above/behind the alternator.
Sorry, I wasn't trying to bust your chops. I just didn't want to see you spend bucks on a new pump if that wasn't really the problem. The aux. pump can burn out the CCU, but it's not the only possible cause (a dragging blower motor can have a similar affect, for example). I would try jumping 12V to the pump and see if it runs, as well as measuring the current when it's energized. If the pump is not the problem, you don't want to install another CCU until you find the issue.
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  #13  
Old 12-30-2005, 07:51 PM
Craig
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Quote:
Originally Posted by d.delano
Will there be anything special that I have to do i.e. 'burp' the coolant system or something to get the air out that I introduced with the installation of the new pump? I'm going to do this without draining the coolant as I just replaced it and just don't want to replace it again.
If you clamp off the lines I would expect you to lose very little coolant. I would just turn on the heat and refill the bottle as required, then recheck it in a day or so.
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  #14  
Old 12-30-2005, 08:05 PM
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As a contributor to many forums other than this one I need to tell you folks that this is the most repectful and courteous forum I have had the pleasure to be part of...You should try the Car Audio forums full of 20 somethings where they are all experts and opinions are fine as long as they are the accepted norm. The political forums are full of angry voters that aren't getting their way and moderators regularly have to scold members for name calling and keeping the hate mail down....I never have to worry about being called names and my opinion is respected....Thanks for all the nice posts...
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  #15  
Old 12-30-2005, 09:33 PM
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Quote:
Originally Posted by d.delano
Excellent. Thanks to all. To recap, I shall-

1) Put a 1A inline fuse in the replacement pump, pos wire
2) clamp off the two heater hoses
3) pull the old pump
4) install new pump
5) pull old fried CCU that I had just fixed(DOH!!!)
6) install new 'used' one that I just got, hope it ain't fried (ain't seen it yet but my nose knows)

Will there be anything special that I have to do i.e. 'burp' the coolant system or something to get the air out that I introduced with the installation of the new pump? I'm going to do this without draining the coolant as I just replaced it and just don't want to replace it again.

You all know I drive an MB diesel so I can't do a fool thing like never post here again
Interesting that you have the same problem that I had last week on the SD. My blower would not work and I spent the better part of a month checking for all the usual blower issues.

Turns out that the CCU was fried........and.........yes..........the aux. water pump was the culprit.

So, I pulled the pump from the SD and connected it up directly to a battery. No rotation but it pulled 2.5 amps. So, Brandon, a stalled pump won't pull tens of amps........only 2.5 amps........and that will fry the CCU, given sufficient time.

So, my advice is to remove the old pump and connect it directly to a battery with an ammeter inline. See if the pump rotates and read the amperage. If it's less than 1 amp, then the pump is fine and the problem lies elsewhere. If the pump fails to rotate, read the amperage and report back with the results. I'm curious if you can repeat my results at 2.5 amps for a stalled pump.-
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