well, my experience was a very noticable difference when mine stopped and again when I fixed it. I suspect that a lot of highway driving you might not notice. But if mine quits again, I bet I know right away.

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

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

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

My son was able to find the brushes and cleaned everthing up and I now have much more cabin heat in town than I did before. Will just hope that it does not start to leak. Thanks for the quick response to my question.
JOHN

I wanted to clarify my point made earlier. I never stated that the pump was for emmisions. I stated that it was used to improve cabin warm up, which is a government regulation. All car manufacturers must meet specific criteria to defog the winshield in order to sell cars. Mercedes must have had a problem with cabin warm up or they would not have installed it. It draws more power which affects fuel economy, has more leak paths and adds wiring.
I am glad to hear it helped out.

The design of the 617.xxx engine warrents the use of a pump at idle if you want to get serious heat out of the car.

Since the w126 was a pretty high end car, I am sure they took this into consideration. Nobody would buy such an expensive automobile if you got in it and the heat was a weak point. I know that my SD can actually cause pain to my skin if I have the heat going good.

The pump draws 1amp or less when running (HARDLY a power draw compared to the heater motor, AC compressor clutch, etc.)

For how quick my car can clear the windows of fog on a cold morning I see exactly why they put that pump in there.

BTW...299700k and origional pump...

That pump won't help clear your windows on a cold morning until the engine warms up. And, you'll sit there in the driveway for 15 minutes until that happens.

Just drive it.......the windows clear........without the pump......once the engine temp gets above 50°C. or so. I've done it both ways........there's no difference.

If there was no difference you can be sure that mercedes engineers would not have spent the money on something attached to car that was otherwise reasonably simple and straightforward.

There is no difference at temperatures greater than 25°F.

I'm sure that the pump is there for a reason for those who live in Siberia or equivalent.

I removed my aux pump 2 years ago (W123) and always have plenty of heat. Sure, if it idles for a long time, the temp cools off a little, but it is almost not noticeable, and certainly does not warrant putting a pump back in.
Granted, it lives in California...

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Think Alternative Energy!
300CD '80 (now gone but not forgotten...)

I also need to replace my aux. pump also. I have a 92' 300e, it has heated washer fluid. The aux pump has a 2nd outlet to the washer tank, the small hose going up.(see attached photo). Wherever I look to buy a replacement pump all photos only show 1 inlet and 1 outlet for the pump. Does anybody know if the hose attachment end is interchangeable with a new pump. Your input would be greatly appreciated.
Thanks

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1992 300E 120,000