Question regarding auxiliary water pump. - PeachParts Mercedes-Benz Forum

cityhix · #1 02-03-2008, 03:18 AM

Hey, ya'll.

I have a bad auxiliary water pump I would be willing to sell cheap (or trade for a good one)........just kidding.

But seriously, I know that a seized pump can do damage up the electrical stream, since it is unfused. If this has happened to me how would I know? What gets fried when the pump locks up? The car came to me with a bad pump, which I now have disconnected. I will be replacing the pump soon and would like to know what else might need to be fixed to get it working again.

Thanks, and I need to go to bed. I'm getting dopey.

turbobenz · #2 02-03-2008, 03:39 AM

On my first car, the 84, it was seized also. I was dirt poor, and still am so I took it apart and wd-40'ed it and it worked fine. There was no damage to anything upstream. If a motor has seized, it doesnt exactly mean its shorting out, sure it will consume more current than usual, but it wont be a short circuit.

cityhix · #3 02-03-2008, 03:47 AM

OK, so I'm dopey enough the I missed a thread from the archives on this subject. I now know that what can occur is fried circuitry in the ACC control unit. So, taking this further, does the aux pump normally operate only when the ACC unit says "make heat"?

Maybe someone will help me understand what parts of my system are not working, and what are. These are the facts:

-aux pump is kaput (tested direct to battery and I get nothing)

-defrost works and is nice and hot if the engine temp is up and RPMs are high enough to get coolant into the heater core

-bilevel works through defrost and far left and far right vents (again if hot and moving)

-floor vents front and back get no air at any temp

-temp control wheel seems to have no affect on bilevel or defrost

-A/C is totally non functional (no belt to A/C pump)

What would make me happy (in the CC department anyway

):

-a working aux pump that will keep the heat coming while waiting at a stoplight

-working defrost (already have)

-working bilevel with the addition of floor heat in front (I need to learn how to prop open the floor vents)

What I would be willing to do:

-bypass servo and add a cable controlled valve (only if it sounds like the ACC system is beyond help)

-remote switch for the aux pump (in case the ACC unit is fried and won't allow a new aux pump to get power)

To sum up, I just want hot defrost, dash vents and floor vents, and don't mind using brute force to get it!

All comments appreciated.

cityhix · #4 02-03-2008, 03:50 AM

Quote:

Originally Posted by turbobenz

On my first car, the 84, it was seized also. I was dirt poor, and still am so I took it apart and wd-40'ed it and it worked fine. There was no damage to anything upstream. If a motor has seized, it doesnt exactly mean its shorting out, sure it will consume more current than usual, but it wont be a short circuit.

I've found a couple of descriptions of repairs to the pump and I just might try it (though I have found them new at ************** for only $75). Thanks for the tip! Would be nice to get it working for nothing!!!

turbobenz · #5 02-03-2008, 05:18 AM

Quote:

Originally Posted by cityhix

I've found a couple of descriptions of repairs to the pump and I just might try it (though I have found them new at ************** for only $75). Thanks for the tip! Would be nice to get it working for nothing!!!

Btw since some of your vents dont work that means you have vacuum problems

cityhix · #6 02-03-2008, 11:31 AM

Quote:

Originally Posted by turbobenz

Btw since some of your vents dont work that means you have vacuum problems

Definitely something to track down eventually. Any tips on propping those floor vents open? I have poked around with a long screwdriver (gently) in what appears to be the outlet for the front floor heat and I can't seem to locate a vent flap.

Jeremy5848 · #7 02-03-2008, 11:57 AM

1. It may be possible to disassemble and repair the auxiliary pump -- others have done it, as posted here. OTOH, you can simply remove it and substitute a piece of pipe. The aux pump helps primarily at low engine speeds, city traffic, etc. The old farts (like me) who buy Mercedes complained that there wasn't enough heat -- that's why the pump was installed. You can do without it.

2. The lack of heat to the floor vent most likely means a bad pod, as was just said. They are rebuildable and replaceable -- rebuilding is less expensive, of course. You remove it, replace the broken diaphragm, put it back in place. Search the forum for instructions. Temporarily (permanently?), you can remove the link from the pod to the floor vents and wedge them open -- I had to do that on a winter trip last year. I posted pictures here somewhere.

3. Bilevel sends heat to the windshield, the left and right vents, and the floor ducts. Center vents are for a/c only (although that can be changed).

4. The temp control wheel failure to work probably means that something is fried in the ACC pushbutton unit or the servo. I have never heard of anyone rebuilding their own servo. Rebuilt units are expensive and modern redesigned servos also. You could add a mechanical valve controlled by a cable from the cabin, I suppose.

Jeremy

LilTimmy · #8 02-03-2008, 12:19 PM

Have you tried your local import parts store? I got one for my car for about half the price of the ************** one and didn't have to wait for shipping. Seems to be the case with most of the stuff they sell on that site.

cityhix · #9 02-03-2008, 12:33 PM

Quote:

Originally Posted by LilTimmy

Have you tried your local import parts store? I got one for my car for about half the price of the ************** one and didn't have to wait for shipping. Seems to be the case with most of the stuff they sell on that site.

I haven't found a local source and, in fact, they (**************) seem to have the best price that I can find online for that particular item (aux water pump). Best price for Bilsteins that I have found also. Other things, not so good.

cityhix · #10 02-03-2008, 08:23 PM

I pulled the pump out today, hoping that a disassembly, cleaning and lubing might get it going again. No dice-it looked like it must have stopped working years ago. The screws sheared off due to be being seized and corroded and the inside was a mass of rust and crud. Luckily, I had some heater hose, clamps and an elbow so I got everything back together (less the bad pump). Maybe the flow will be better now!

Also, I figured out how to prop the floor vents open. It was cool figuring out which vacuum pods operate what. Now I know which one is bad!

unkl300d · #11 02-07-2008, 08:08 PM

If you are getting heat then your acc amp is working. If your battery has not been drainiing then your Klima servo is not stuck in the ON position. So you can bypass it and keep the amp in place hoping your A/C will eventually come back to life. Otherwise just pull the amp out also.

Don't bother repairing the temp selector wheel if in fact it is defective. If your ac is broken, you don't need it.
If your Klima servo is broken then you might as well bypass it and after that you still don't need the temp selector because that system has been bypassed.
The only thing that serves function on that module are your fan selector buttons and A/C power switch.

If you end up bypassing your Klima servo, I would not bother buying a new aux water pump.
Waste of money.
True it does increase the flow of hot air (water) intensity at idle but definitely not worth the bucks.

Wait until you go to a pick n pull and get it for $4 if you really MUST have it.

If that pump was so dirty, you need to back flush your coolant system and the heater core.
Get the mud out.

Don't waste your money.

unkl300d · #12 02-07-2008, 08:14 PM

p.s. there is a lad up your way north selling parts off a 79 300D...go to parts threads

cityhix · #13 02-07-2008, 11:30 PM

Quote:

Originally Posted by unkl300d

p.s. there is a lad up your way north selling parts off a 79 300D...go to parts threads

I can't locate this thread.....

cityhix · #14 02-07-2008, 11:38 PM

Quote:

Originally Posted by unkl300d

If you are getting heat then your acc amp is working. If your battery has not been drainiing then your Klima servo is not stuck in the ON position. So you can bypass it and keep the amp in place hoping your A/C will eventually come back to life. Otherwise just pull the amp out also.

Don't bother repairing the temp selector wheel if in fact it is defective. If your ac is broken, you don't need it.
If your Klima servo is broken then you might as well bypass it and after that you still don't need the temp selector because that system has been bypassed.
The only thing that serves function on that module are your fan selector buttons and A/C power switch.

If you end up bypassing your Klima servo, I would not bother buying a new aux water pump.
Waste of money.
True it does increase the flow of hot air (water) intensity at idle but definitely not worth the bucks.

Wait until you go to a pick n pull and get it for $4 if you really MUST have it.

If that pump was so dirty, you need to back flush your coolant system and the heater core.
Get the mud out.

Don't waste your money.

I think that what I am going to attempt is to bypass the servo and not even put in a valve. If I get more hot than I want then I will go ahead and rig up the valve and cable. Do I need to cap off the inlet/outlet to the servo if I don't bypass the other side? Or will I be spewing coolant?

I like the sound of skipping the water pump replacement. I can always do it later.

And good point about doing a coolant flush. Is this something to be trusted to your average franchise repair shop? I will search threads for recommended techniques.

Thanks...

unkl300d · #15 02-08-2008, 03:12 PM

Theoretically, if your servo is not cracked, you can bypass only the inlet side and leave the outlet side connected thru the servo. I think that is how ************** sells their kit. Test it.
However, if your servo is not rusted in a stuck position inside (interior leaks happen also, not visible as external leaks), you might later consider bypassing the outlet side in order to save the possibley working servo mechanics/electronics from future leaks and rust.. That way you can keep the amp installed and maybe revive your A/C.

Just back flush yourself instead of hiring.

buy a garden hose attachement to stick into the open heater hose (use a hose clamp if needed, then detach the outlet side hose and divert it into a bucket.
Attach garden hose and flush away.
you gain by knowing the actual 'before and after' condition. flush until clean.
use store bought water and a good antifreeze like MBZ coolant for refill.
Flush or drain your radiator while u r at it. easy.
top off via the top radiator hose to prevent air bubbles.
not hard. just get organized and take your time.