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Old 10-27-2006, 07:16 PM
mgburg's Avatar
"Illegal" 3rd Dist. Rep.
Join Date: May 2006
Location: Onalaska, WI.
Posts: 221
*** Air Pump Query ***

I've never understood the purpose of the air pump ...

What exactly is its purpose?
How important is it?
If it drastically is performance affected?

As it stands at this time, the air pump is making a "growling" sound as you start the car up and it quiets down about 10-15 seconds after the car starts to idle. I'm sure I'm seeing/hearing the beginning of a problem. I want to take care of this before it gets too cold and I end up getting a call from the wife - stranded someplace unpleasant.

And last, but not least, how many $$$s for either a new, or re-manufactured (if possible) unit.

Thanks in advance for any information.

BTW, this AP is in a '77 280E unit, the engine is the 110.984 series.



M. G. Burg
'10 - Dakota SXT - Daily Ride / ≈ 172.5K
.'76 - 450SLC - 107.024.12 / < .89.20 K
..'77 - 280E - 123.033.12 / > 128.20 K
...'67 - El Camino - 283ci / > 207.00 K
....'75 - Yamaha - 650XS / < 21.00 K
.....'87 - G20 Sportvan / > 206.00 K
......'85 - 4WINNS 160 I.O. / 140hp
.......'74 - Honda CT70 / Real 125

“I didn’t really say everything I said.”
. . . . . . . . . . . . . . . . . . ~ Yogi Berra ~
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Old 10-27-2006, 11:56 PM
wbain5280's Avatar
Registered User
Join Date: May 2001
Location: Northern Va.
Posts: 3,386
The air pump adds air to the exhaust ports to promote complete combustion. If it makes a noise, the bearings are bad. Look at the 'Buy Parts' link at the top of the page for a replacement, or get another used one from the junk yard. (Look for your car and the part is in the Air Intake section)

It appears to be a Saginaw (GM) air pump, so availability is good.

Click on your car.


Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL


Not part of the in-crowd since 1952.
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Old 10-28-2006, 08:56 PM
Registered User
Join Date: Jun 2005
Location: Copenhagen, Denmark
Posts: 39
Yes, it adds air (oxygen) to the exhaust to boost catalytic converter operation until oxygen sensor heats up and controls the fuel mixture for correct oxygen balance.

This only happens initially after starting the engine, and it does have some noise during that time.

Of course, I can't hear wether your noise is usual or not.
1991 300SEL (W140)
1987 190E 2.3 (W201)
1987 Honda Accord 2.0
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Old 10-28-2006, 09:05 PM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,804
< __________________

What ???
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Old 10-28-2006, 09:38 PM
Larry Delor's Avatar
What, Me Worry?
Join Date: Jun 1999
Location: Sarasota, Fl.
Posts: 3,114
Originally Posted by Arthur Dalton View Post
< __________________

What ???
I think he means: Louder than is normally acceptable.

It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein

09 Jetta TDI
1985 300D
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