Arrrgh! Auxilliary coolant pump leaking..... - PeachParts Mercedes-Benz Forum

rwthomas1 · #1 03-31-2003, 06:47 PM

Okay, I might have finally found the last coolant leak in my car. Unfortunately the coolant is leaking from my auxilliary coolant pump. Pump still runs (I hotwired it) and it is getting 12volts so I believe the ACC is okay. (Seems to work fine) Fastlanes got pumps for $130 and PP for $108, a little steep right now. So here are my questions:
1) Can these things be rebuilt/resealed?
2) If so how do I test the pump to make sure its not pulling too many amps? (I'm an idiot with a multimeter)
3) Since its almost summer and I won't be using the heat much anymore can I remove the aux. pump and install a copper plumbing elbow in the line until I get some extra cash together?
4) Will this hurt anything and will my ACC still function (for cooling) okay?
5) Anyone got a used pump that they are willing to part with?
I already did a search on this and I can't answer these questions.
Thanks for the help, RT

engatwork · #2 03-31-2003, 07:08 PM

You can remove the pump and put in a pvc or copper elbow. Even if you use the heater I am under the impression you will not really miss the pump unless you are sitting at idle for awhile. It will not hurt anything to run with it disconnected. Not sure if they can be rebuilt. Not sure about testing for hi amps.

Fredmburgess · #3 03-31-2003, 09:57 PM

Hey RT,
I just put in a used pump that I bought for $35, I think. My old one didn't leak, but the motor was shot. Have to go have a look at it in the garage but I think you can separate the motor and pump, so maybe you can add my pump to your motor? Just send me a note with your address and it's yours.

..I read an earlier thread indicating that a seized pump or motor could fry the circuit board in the in-dash push botton CC unit. In fact, that was one of the things I replaced ($$$), so I'm going to insert a 1.5 amp fuse in the line to the aux pump motor. Rather replace a fuse than the cc unit!

FRED

rwthomas1 · #4 03-31-2003, 11:58 PM

Fred I just sent you a pm with my address, thanks for the offer! I plan to use a relay (LarryBibles idea) switched by the ACC to turn on the pump and also a fuse to the pump to completely isolate it from everything. Hopefully I can make a good pump out of two bad ones? Worth a shot anyway. RT

lrg · #5 04-01-2003, 12:00 AM

RT,
I just replaced a fried CCU that I believe was done in by my frozen (as in siezed) circulation pump. The actual pump can be separated from the motor and taken apart. It's pretty simple so there's not much you can fix. I got mine going again and wired in a 1.5 amp inline fuse. It was a good thing too because I later found the fuse blown and the pump frozen again. After one more futile attempt to fix it I just left it with the blown fuse. I have a hard time spending $100+ for a new one. Granted it doesn't get too cold here but we still use the heater a lot in the mornings and I can't tell the difference. Leaving the pump inline doesn't seem to hurt the heating much if any. You may miss it next Winter when it's 20 below but otherwise I'd just unplug it and forget about it for now.

rwthomas1 · #6 04-01-2003, 12:05 AM

LRG,
I can't forget about it as its leaking.... I may just put a copper elbow in and leave it be but I need to stop the leak. RT

lrg · #7 04-01-2003, 12:14 AM

Understood. You should be able to transfer Fred's pump. The tricky part is getting the impeller off the shaft. I was able to lever mine off very carefully. Just to be on the safe side I ran the pump (but not the motor, obviously) under hot water in the hopes that the expansion would help and the heat would make the plastic less likely to crack. Give it a try. If it doesn't work go with the pipe replacement. Based on my experience you'll have no problem running without the pump. Good luck.

R Leo · #8 04-01-2003, 07:24 AM

Go get one at a junk yard. It should be much cheaper than singlehandedly suppporting your local profit center

Just find a recently wrecked car and pull it off...the pumps are all pretty much the same but the mounts differ from model to model...

Some yards have a minimum charge so be sure and pick up all the other trinkets that you've been needing for your Benz too.

Regards to all,
R

rwthomas1 · #9 04-02-2003, 12:27 AM

Heres what I did:
Purchased a used aux. pump at local yard. Yanked it out of an 82SD, couldn't pass it up for $5. Installed "new" pump. I grabbed the connector from the SD as well. I wired in a 15amp relay which is latched by the factory pump feed. Inline fuse just in case. Also 10amp inline fuse on the new hot from the relay to the pump. I left the pump ground hooked up the original way. By taking the connector from the SD and cutting the other connector off my bad pump I was able to make a wiring harness that simply plugs into the factory setup. This way I didn't have to cut any wires on the car. I do have a question though:

I installed a 1.25amp/250volt "fast acting" fuse in the factory pump feed that now latches the relay. It blew on the test drive. I know nothing about fuses. I don't think the "bosch" relays pull more than 100milliamps so I should be fine???? I put a 5amp in to test and all is working fine. What should I try? I am thinking a 1.5amp slo-blow fuse? How do you test for amp load on the relay?

FredmBurgess, I know you just shipped me a dead pump and yes I still want it. I plan on doing a rebuild and having a spare. Thanks again, RT

P.E.Haiges · #10 04-02-2003, 10:17 AM

RWThomes,

You should measure the current going to the relay coil terminals. It seems to me that you have a problem if you blow out a 1.25 amp use. Are you sure you didn't have the motor wired into the 1.25 amp fuse? It doesn't seem to me that the "coil" in the relay should draw enough current to blow a 1.25 amp fuse.

SLO BLO fuses are used for devices that draw a heavier current at starting and then run at a nominal current. Motors typically do this.

If your circuit is drawing more current than the fuse is rated for, a SLO BLO fuse will still blow out only not quite as fast.

P E H

rwthomas1 · #11 04-02-2003, 02:13 PM

PEH,
The motor is definitely not wired to the 1.25amp fuse, only the original power wire which is now ONLY use to drive the relay is wired to that fuse. A bosch style relay should require less than an amp. The pump motor is wired through the power side of the relay with a 10amp fuse. I have done some research and found that sometimes when using a device like the ACC to drive a relay it cannot withstand the negative voltage spike created when the relay "unlatches". To combat this I have now installed a 200watt/1amp diode across the ground/switch lugs with the cathode side of the diode to the switch. This will prevent/quench the voltage spike from possibly damaging the ACC. I have also installedupgraded to a 1.5amp slo-blo fuse on the drive/trigger wire from the ACC. Hopefully this will do it. How do you measure current draw from the relay? I have a fairly sophisiticated meter but not a clue how to use it. RT

Fredmburgess · #12 04-03-2003, 03:01 PM

Holy Cow, RW... All I did was slap in a new pump with a 1.5 amp fuse in the hot wire, pump side of the plug! So far so good! Anyway, good luck with all the stuff you're doing. I'm an idiot when it comes to parts that don't move (ie; circuit boards, diodes, etc.!). f

#13 12-05-2003, 02:57 AM

MB300DT

Where is the Auxilliary Coolant Pump located? What does it look like?

#14 12-05-2003, 03:10 AM

Is the Auxilliary Water/Coolant Pump aka Circulating Pump?

R Leo · #15 12-05-2003, 09:29 AM

Quote:

Originally posted by 84W123DT
Is the Auxilliary Water/Coolant Pump aka Circulating Pump?

Yes. On W123 and W126 chassis it is located in the engine compartment, on the right side of the car, bolted to the inner fender beneath the engine air intake. It has two hoses (one from the monovalve-on the firewall and one going to the thermostat housing) and two wires going to it.