Auxiliary Coolant Pump - PeachParts Mercedes-Benz Forum

rrodz · #1 05-31-2006, 03:46 PM

Is it supposed to work every time I put the key in the ON position? I used to hear it when the engine is shut down. Not any more though, and I can't tell for how long.

I don't see any changes in the engine temp. Is it supposed to be ON all the time?

I will start with the fuse box. I saw a price of $160 for that little pump. Looks easy to change though.

Please, please don't kill me, but I have'nt changed the coolant at 99K miles and 7 tears assuming it should not be a problem in FL, I will change it now. I know MB coolant only, I read the threads.

Thanks,

Rene

mbdoc · #2 05-31-2006, 04:06 PM

Aux water pump is mounted to the firewall not in the fuse box...should run any time the engine is running & for 10 minutes after shut-off.

rrodz · #3 05-31-2006, 04:14 PM

Thanks Doc,

So it is not running then, dead.

About the fuse box, what I meant is to check for a blown fuse related to this pump first before I do anything else.

So if the fuse is Ok, then I should go ahead and get a new one.

Rene

mbdoc · #4 05-31-2006, 05:21 PM

That would be fuse # 41 & also relay k19...........

rrodz · #5 06-01-2006, 06:41 AM

Doc,

Checked the fuses and these are OK. The interesting thing is that I also checked my C280 and the pump seems not to be working either. Is this a common problem? Looks like I need 2 pumps now.

Rene

checked relays too by swapping with a known good one.

mbdoc · #6 06-01-2006, 08:04 AM

The c-class system operates differently than the ML...should function when asking for heat. Also for engine after-run ONLY if the engine reaches 110C.

jfreezn · #7 06-05-2006, 02:04 AM

Quote:

Originally Posted by rrodz

Is it supposed to work every time I put the key in the ON position? I used to hear it when the engine is shut down. Not any more though, and I can't tell for how long.

I don't see any changes in the engine temp. Is it supposed to be ON all the time?

I will start with the fuse box. I saw a price of $160 for that little pump. Looks easy to change though.

Please, please don't kill me, but I have'nt changed the coolant at 99K miles and 7 tears assuming it should not be a problem in FL, I will change it now. I know MB coolant only, I read the threads.

Thanks,

Rene,

On my 98 ML320, I had opened the hood just after shutting off the engine, and my aux water pump was starting to smoke! Knowing I had the keys out of the ignition, I made great haste to unplug the little pump's power connector, but in the 2 to 3 minutes it took me to do this, the pump became so hot it was melting the plastic, and appeared like it would burst into flames. I removed it completely, replacing it with a high temperature synthetic elbow from the plumbing dept at Ace hardware. Go with the fittings used for plastic pipe used for HOT water distribution in homes. NOT PVC!

I am sure this pump is controlled by the AAM (All Activity Module), and as the Doc says, it was in it's 10 minute run on period. It is not a necessary feature to get heat in the passenger compartment, at least in Arizona. Save your $160!

I have also removed the aux hot water pump from my 79 300SD, and have not needed it to get heat for several years.

Jim in Phoenix

ML Dude · #8 04-04-2009, 02:15 AM

I know this is a very old thread, but MB Doc if you are around, or anyone else! I mistook my recirculating valve for the aux water pump and removed it. I then tried to take it apart and moved the single torx head adjusting screw which is factory sealed. Now I need to know how this is set so I can try to adjust it back to factory settings. btw, where on the firewall is the aux water pump?

ML Dude · #9 04-06-2009, 02:21 AM

It seems what I fiddled with is called a purge valve. Now if someone can tell me what that is for and how I might know if I need a new one, I'd be grateful. What would the driving symptoms be of a bad purge valve.