Tell me what you know.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

Skinny?? It's actually rounded and pumps water for the heating/air cond. system. Do you actually have a specific question?

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Sam

84 300SD 350K+ miles ( Blue Belle )

When you run out of fuel, the auxiliary water pump kicks in and pumps water quickly through the engine, backdriving the impeller in the primary water pump which drives the fan belt and thus the engine crank pulley. It's not too powerful, but it's usually enough to get you home if you are only a few miles away.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

So that's why MB put those big batteries in the diesel cars!!! I have wondered about that for years. Now I know.

Please note that you have to be careful when you do this. If the auxiliary water pump gets too much current, it will spin too fast and the vehicle might accelerate, uncontrollably, up to 80 mph for a short distance.

Nice one Pete !!
Useful to know with diesel fuel prices the way they are - maybe we can switch it on all the time as a "helper" drive.

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1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

LOL

Well my SDs was missing along with the monovalve, the heat stays on ALL the time if it's not there.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Wow, this forum is going to **** now right along with benzworld. You guys never heard of the expression "the skinny" ?

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

Perhaps it would help if you asked a specific question. What do you want to know about the aux. water pump?

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Keep everything as simple as possible-but no simpler--Albert Einstein

I justed wanted someone to chime in who has some experience with it. Where it is. What is it. When it is used. etc, etc. I know the very basics on this.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

In a day when many of these new "wonder cars" are called "Hybrid cars", maybe we should call this wonderful heater water pump drive the "halfbreed" drive. My bus has it also. Buses are usually halfbreeds.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

You should be able to answer most of your questions by using the search function-I imagine that is why they are messing with you.

To briefly answer your questions, though, I believe on most models it is located inside the dash near the firewall; it pumps water through the heater core-apparently the main water pump does not provide sufficient flow under idle to heat the interior; it is on all the time.

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Keep everything as simple as possible-but no simpler--Albert Einstein

Just couldn't resist, today, I guess.

On the SD, it's located between the two firewalls, toward the passenger side of the compartment. It's a PITA to get to if you need to change it. Sometimes removing the section of the forward firewall makes it easier.

As previously mentioned, it serves to move coolant through the heater core because the normal flow of the water pump is inadequate.

Some have recommended to put a 1 amp fuse on the pump. If it gets old and draws too much current, it takes out the PBU.

I need to do this.

It helps to know specificly what year and model you are asking about too as they are not all in the same location. And yes I know its in your sig file.

It pumps water for the heating system at low speeds. The way the system is laid out the main waterpump doesent provide suficient pressure unlike most other cars.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

On a W126 it is located underneath the Monovalve in the space between the engine firewall and the cabin bulkhead. It's a pig to get at and so is often ignored.
It is only known to fail between November and March (in the Northern Hemisphere at least) and will probably sieze and blow the #5 Fuse which also feeds your A/C Compressor Clutch and the ACC.
As Habanero has said it is used to boost the water flow through the Heater at low engine speeds. System works fine without it (ask how I know ) so unless you do a lot of slow speed town driving it is not a high priority to get fixed. Just disconnect it electrically to avoid the fuse blowing already mentioned.

__________________
1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown