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  #1  
Old 01-28-2008, 07:40 PM
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Bad auxiliary water pump-temporarily bypass for more heat?

I have tested my auxiliary water pump and determined (?) it to be not working. I intend to replace it, eventually, but I am wondering if a non working pump constricts coolant flow enough that bypassing it might improve heat delivery at low RPMs (ie freezing a** off at stoplight)?

While I'm at it, tell me if I failed at the test of the pump: I simply pulled the pigtail, hooked up leads to each prong then touched the leads to the battery terminals. Neither combo of pos/neg or neg/pos caused the pump to do anything. Bad?

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Old 01-28-2008, 07:43 PM
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Quote:
Originally Posted by cityhix View Post
I have tested my auxiliary water pump and determined (?) it to be not working. I intend to replace it, eventually, but I am wondering if a non working pump constricts coolant flow enough that bypassing it might improve heat delivery at low RPMs (ie freezing a** off at stoplight)?

While I'm at it, tell me if I failed at the test of the pump: I simply pulled the pigtail, hooked up leads to each prong then touched the leads to the battery terminals. Neither combo of pos/neg or neg/pos caused the pump to do anything. Bad?
Nah, leave it in place.
Won't make a significant difference.

Keep it unplugged, a bad aux pump can affect the HVAC control.

Jim
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  #3  
Old 01-28-2008, 07:46 PM
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The bad pump may have already done damage. I can't say that I have actually got a handle on what works with the ACC, so I don't yet know what doesn't work.

I tried to figure out how to prop the floor vents but I can't even see what to prop!
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Old 01-28-2008, 07:56 PM
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If the pump did nothing when you provided it direct power then it is dead. Both my 300SD and 300D had dead pumps. Replaced it on the SD to improve heat in the car, but on the 300D I get plenty of heat even with it unplugged. Leave it unplugged if it is dead, it can fry the CCU board as there is no fuse. (CCU board becomes fuse...not good)

I need to prop the floor vents open on our 300D too.....all the heat is at the defrost and two side vents.....cold feet + charred face!
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  #5  
Old 01-28-2008, 09:13 PM
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my 300sd has had the pump unplugged for 7 years....just after it fried the ACC unit. I only live in missouri so it does not get below 20F very often and have minimal loss of heat at stop lights. IMO it's not worth the cost or hassle to replace it.
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Old 01-28-2008, 09:29 PM
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Fuse

If you do replace it, add a fuse! An ampere or two is sufficient, prevents a future bad pump from frying the ACC board.

I did a DIY with photos on that subject here.

Jeremy
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Old 01-28-2008, 09:33 PM
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Maybe before I buy a new pump, maybe I should figure how to get the engine temp up faster................sound of new can of worms being opened.
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Old 01-28-2008, 09:37 PM
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Originally Posted by cityhix View Post
Maybe before I buy a new pump, maybe I should figure how to get the engine temp up faster................sound of new can of worms being opened.
It should take 2-5 miles (depending on speed and outside temp) for a 617 (probably 616 too) to get up to a steady 80-82C engine operating temp....if this is not happening, its probably your engine thermostat.
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  #9  
Old 01-28-2008, 09:38 PM
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Quote:
Originally Posted by Jeremy5848 View Post

I did a DIY with photos on that subject here.

Jeremy

W123 aux water pump fuse install w/pix


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  #10  
Old 01-28-2008, 09:54 PM
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OK, so here is my morning routine (morning temps have been hovering around freezing (low of 25 F)):5-10 minutes before I want to leave, I go outside, plug in electric heater that I keep in the car, go inside, brush my teeth, go back out, start car, go back in, feed dogs, put cell phone in pocket, go back out, unplug heater, hit the road. At this point the car has been running for 5-8 minutes (too much idling probably) and the temp gauge is reading approx 120F. I get on the freeway, drive maybe 3 miles, off the freeway another 3 miles or so to the office, by the time I'm to work the temp is reading about 175 F and the defrost is blowing pretty warm, as long as I'm going over 30 MPH or so. Oh yeah, temps in Fahrenheit because its a 1979.

Does it sound like too long to get warm? Thermostat bad?
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  #11  
Old 01-28-2008, 10:58 PM
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Yes, it does sound like your thermostat is bad, it should be up to temperature very quickly on the freeway and should stay there after coming off the freeway.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 90k - mine - (OC-91,200)
'17 Metris(VITO!) - 18k - wifes (OC-25k)
'01 E320 Wagon - 161k - mine (OC-165,000)
'01 E320 - 180k - dad's (OC-182,500)
'07 E350 Wagon - 134k - dad's (OC-139,500)
'01 SL500 - 56k - dad's (OC-59,000)
'16 E400 4matic Sedan - 81k - Brothers (OC-88,000)
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