No heat. Auxiliary Pump would help? - PeachParts Mercedes-Benz Forum

trt · #1 05-10-2008, 01:47 AM

1980 300D.

I had a/c but no heat. Then a/c stopped working, too.

I just had the servo replaced as it was cracked and leaking.
There is still no heat. The tech thinks that the aux. pump needs to be replaced and this would fix the heat issue. (I assume he means aux water pump mentioned here). Does this make sense?

From reading the other threads I noticed that the aux water pump can be removed and that its function is to increase the amount of heat.
I have no heat at all and the a/c is iffy.

Where is the $75 aux water pump on mercedesshop?

If I decide to remove the aux pump, what kind of hose do I need to put as a replacement or should I just unplug it.

If I decide to replace the aux pump with a new pump is it a simple unplug and replace or does anything else need to be done before or after?

If the complete lack of heat has nothing to do with the aux pump, what is causing it?

I am also coming across this part called the "electric water pump" which looks very similar. Is it the same as an aux pump?
MBZ037173
MTC/Ronak Electric Water Pump
w/ auto climate control; 15mm hose connections; 13 inch long cable; w/ 15mm hose connections & 13 inch cable length; Packing Size

IECE; Qty Per Vehicle:1;

trt · #2 05-10-2008, 05:50 PM

bump. any advice...

Jeremy5848 · #3 05-10-2008, 06:31 PM

If the aux water pump is seized (not turning) and/or clogged up so no coolant flows through it, then you will have no heat. You can replace the pump with a piece of pipe as a test. If you are in a warm climate you really don't need it anyway. The aux pump is located on the right side of the engine bay, just behind the alternator.

Another possibility is that the heater core is clogged so that no coolant is flowing through it.

Jeremy

kerry · #4 05-10-2008, 06:48 PM

You can test the auxilliary pump pretty easily by jumping 12 volts from the battery directly to the pump and see if you can hear it running. It doesn't sound like a bad pump to me though. However, if the pump seizes, it can take out the climate control amplifier. Perhaps this combination is the source of your problems.

tobybul · #5 05-10-2008, 08:40 PM

I didn't think the 80 300D had an aux pump..... mine doesn't and I have great heat.

kerry · #6 05-10-2008, 08:58 PM

I thought all 123's had auxilliary pumps.

#7 05-10-2008, 09:03 PM

Quote:

Originally Posted by kerry

I thought all 123's had auxilliary pumps.

The '80 300D does have it listed on fastlane:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ42D7190AJH&year=1980&make=MB&model=300-D-002&category=All&part=Auxiliary+Water+Pump

However, I don't believe the 240d has it (mine doesn't).

Flounder · #8 05-10-2008, 09:43 PM

I went all winter with a piece of 3/4" heater hose and a $5 brass plumbing valve from Home Depot in place of the aux. pump/monovalve, and had great heat.

UT_Tech · #9 05-11-2008, 01:22 PM

The aux water pump (electric water pump) adds flow at idle. When you rev the engine there will be more than enought flow. If you're not getting any heat at all then there's another problem.

Try bypassing the aux water pump with a short piece of 1/2" copper water pipe and 2 feet of 5/8" water line from the your local auto parts store. If you then get a lot of heat it's your servo. If there's still not heat then you've got a plugged heater core.

Please note that both the feed and return lines to and from the heater core are connected to the bottom of the servo. You have to bypass both the feed and return lines at the servo for this test.

tobybul · #10 05-11-2008, 03:25 PM

Quote:

Originally Posted by kerry

I thought all 123's had auxilliary pumps.

My non-turbo has no aux pump.... may be its b/c its a euro? But I tell you, my heat is very good.