Aux Coolant Pump Dead - 87 300D Turbo - PeachParts Mercedes-Benz Forum

a2t · #1 10-13-2006, 10:00 PM

Im getting ready to install Frybrid kit on my 87 300D.

Ive noticed slow heat last winter, and heard the aux coolant pump could be dead. So, I tested mine tonight and sure enough dead as a door nail.

Now I dont know if this will be a problem or not, but it sure would be nice during the veggie kit install if I had some way of puhsing coolant around without the motor. I was hoping to jump the aux pump and let it push the air out. Guess thats not going to happen.

Is there some way to rebuild it? I pulled the washer fluid res and the pump is totally caked with 250k miles of who knows what. Doesnt look hopeful.

I was also considering retrofitting a small electric pump and just hot wiring it to go whenever key on. Although I do not want to risk frying the ACC, and dont really understand how that thing ties into the pump (ie, can I just snip the plug running to aux pump and run new wires?).

Any and all help is greatly appreciated! Oh by the way the monovalve seems fine, being that I get heat when I should (albeit slowly at first) and cool wen I should.

Theres only 1 monovalve right? For some wierd reason the manuals all say there are 2 monovalves. Pretty sure Ive tracked most every inch of hose, dont see more than 1 mono.

Thanks waaay ahead of time.

Paul

nhdoc · #2 10-13-2006, 10:20 PM

I have a MB coolant pump on the shelf in my garage that I pulled out of my '72 which someone tried to jury-rig a second radiator to. If you want that pump pay the shipping and its yours...it worked fine when pulled.

PM or email me through the board if you want it and tell me where to send it to...you'll get a pump and I will clear a spot on my shelf without feeling guilty about throwing away a part I can't use myself...it's a win-win.

#3 10-13-2006, 10:55 PM

Used aux pumps are cheap if you can wait to get one on ebay. Worst case adsitco has new (or mabee reman) ones for $99. You can buy a small electric pump and I think as long as it is 12 volts it won't hurt anything, but those are hard to come by for any cheaper the used MB ones for your car.
I also believe there is general interchangability with 123's+126's. I bought one from a 124 that fit my 123, mabee the seller was mistaken. As for pumping, or rathing priming the coolant lines, I bought a engine coolant flush kit from walmart for $3 something. In the kit is one peice that has a male end on each side the same size as the heater hose. In the middle there is a cap which can be unscrewed, coolant poured in and screwed back on. If you have this peice at the highest point of the hoses that go to the heated filter/veg tank then you can fill your hoses up through the hole. The cap doesn't leak when tight even under pressure. Make sure you put it somewhere high in the system but also positioned so coolant can be easily poured in. I don't think it was necessary though, just make certain the resevoir is full and gravity should take care of the rest. At least that how it worked for me. Getting it to flow enough to heat the tank is another story, but it is about a 617 and the helpful folks at greasecar.

a2t · #4 10-16-2006, 07:01 PM

Marty thanks for the offer! I will pass though, kinda scared about putting a pump that old in just because it may leak.

I went to junk yard and got brushes out of a couple aux pump motors so I will try to just repl the brushes in mine. Unfortunately the bruses are soldered in so it may be a little tricky but we shall see.

I'll let yall know how it goes, I may just get a new one for $138. Dont want leaks in this thing since its a 124 with a #14 head. Plus Im running it all the time to help push fluid all the way to the trunk and back.

#5 10-16-2006, 10:21 PM

When I unplugged my aux pump, the connectors were covered in green corrosion. I had to splice the lines and dispose of the oem connectors as they just fell apart. I really thought my pump was dead but really one of the wires to it was also green and did not conduct. I kept cutting it down looking for wire that looked copper and just when I was about to give up the last 1/8" of wire coming out of the pump worked. I soldered it and used epoxy to keep it in place. Mabee in some cases a pump is considered dead but it is really internal corrosion of wires/connector.
At least on my '84 300d and a greasecar kit, the aux pump only pumps coolant through the heater. One would have to deviate from instructions in order for the aux pump to pump both the heater and tank. This would mean running the coolant line either from the heater back to the tank then to the aux pump, or tank to heater to pump. I'm not saying that wouldn't work. The way greasecar says to do it is splice the line going to the heater run to filter to tank back to in between the aux pump and engine inlet. At least with me this just doesn't work. The engine will run fine just by circulating coolant through the radiator. There is no reason coolant would take a path of 20' of 5/8" hose while it can just go through the radiator. Believe me-I ran the engine for an extensive time in 70f weather to the point were the electric fan went on for some time-no heat to filter/tank. Revved the heck out of it in order to chase out an air bubble which I'm sure now wasn't the problem. Greasecar just said perhaps my waterpump is faulty and there are hundreds of MB's out there working fine. Well my waterpump was replaced in '03 and the temp of the engine is great, and if that wasn't enough I have great heat even with no power to the aux pump. Consequently I spent $ on another pump for the tank circuit separately. This is not what I figured would be necessary when I bought the greasecar kit. I had lots of trouble with other parts of there kit and have not even started on the fuel mods or wiring. So although Frybrid is more expensive, as the saying goes, you get what you pay for. I wouldn't buy it again, even if it eventually works.

dieseldiehard · #6 10-16-2006, 11:09 PM

Quote:

Originally Posted by Mark Tamburrino

As for pumping, or rathing priming the coolant lines, I bought a engine coolant flush kit from walmart for $3 something. In the kit is one peice that has a male end on each side the same size as the heater hose. In the middle there is a cap which can be unscrewed, coolant poured in and screwed back on. If you have this peice at the highest point of the hoses that go to the heated filter/veg tank then you can fill your hoses up through the hole. The cap doesn't leak when tight even under pressure. (cut)

Whatever you do, if you install one of those Tees in your coolant system, DO NOT LEAVE IT LONGER THAN A FEW DAYS!!!! THEN REMOVE IT!!!
here's very good ressons why leaving that Tee in line can spell DISASTER to your engine:
How to use the Prestone flush kit

Want to flush coolant on SDL

http://www.lunghd.com/Tech_Articles/Cooling/BurpAirMod.htm

a2t · #7 10-17-2006, 05:49 PM

This is very good to know. I hate plastic coolant system parts (see my website www.GruvenParts.com).

Far as I know (and I havent actually receieved Frybrids kit), a plastic Tee is installed after the aux pump in line going into heater core. This is permanent, as it provides coolant out to veggie tank in trunk. No temporary Tee with cap here.

But I guess the question remains - if you Tee into that heater hose line, when heater core monovalve does open, what would prevent all the coolant from just running thru heater core and back to water pump, without acutally circulating thru the veggie tank?

Quote:

Originally Posted by dieseldiehard

Whatever you do, if you install one of those Tees in your coolant system, DO NOT LEAVE IT LONGER THAN A FEW DAYS!!!! THEN REMOVE IT!!!
here's very good ressons why leaving that Tee in line can spell DISASTER to your engine:
How to use the Prestone flush kit

Want to flush coolant on SDL

http://www.lunghd.com/Tech_Articles/Cooling/BurpAirMod.htm

Brian Carlton · #8 10-17-2006, 06:03 PM

Quote:

Originally Posted by a2t

Is there some way to rebuild it? I pulled the washer fluid res and the pump is totally caked with 250k miles of who knows what. Doesnt look hopeful.

Pete Burton shows you how to rebuild the pump in this thread:

How to disassemble aux water pump-part 1

a2t · #9 10-17-2006, 06:20 PM

Thanks Brian, great thread.

Let me bump this question back up, its bothering me at the moment...

But I guess the question remains - if you Tee into that heater hose line, when heater core monovalve does open, what would prevent all the coolant from just running thru heater core and back to water pump, without acutally circulating thru the veggie tank?

a2t · #10 10-18-2006, 08:37 PM

I may have figured it out - let me know what you think.

I should run the coolant line after aux pump straight back to veggie tank in trunk. The return line from veggie tank will then go back to a tee, 1 leg of which will go to heater core, the other leg back to somewhere between water pump and monovalve. That way coolant always goes back to veggie tank and can only enter heater core on the return, if that monovalve opens. Otherwise it would just go back to water pump.

Tee in on the return loop. Does this sound right?

Quote:

Originally Posted by a2t

Thanks Brian, great thread.

Let me bump this question back up, its bothering me at the moment...

But I guess the question remains - if you Tee into that heater hose line, when heater core monovalve does open, what would prevent all the coolant from just running thru heater core and back to water pump, without acutally circulating thru the veggie tank?