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Cars & Coffee Killer
Join Date: Sep 2004
Location: State of Failure
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Electric Water Pump
Last night the wife and I went out to dinner. It was a pleasant, cool evening. When I parked the car, I noticed the electric water pump was not running.
When we got home from dinner and I parked the car, the water pump did run. I've noticed the engine runs considerably cooler since I removed the A/C condenser. Prior to pulling the A/C, the electric water pump ALWAYS ran after I shut off the engine. My question is, is the electric water pump supposed to always run, or does it only run when some heat threshold is reached?
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Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
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08-22-2006, 05:37 AM
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Location: Kingsport, TN
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The electric water pump you speak of is for the turbocharger. It should always run for about 20-25 seconds when you turn the key off. It will restart if sufficient heat bleeds into the turbocharger from the exhaust piping and then run for another cycle. If the car is hot enough, this can cause the fans to kick in as well. Mine will run and stop several times when the engine is good and hot.
The purpose of the pump is to keep the oil in the turbocharger bearings below a threshold temperature to prevent deterioration of the oil and, hence, premature bearing failure inside of the turbocharger.
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Lawrence 1986 951 2002 SLK32 AMG 1987 328GTS 2011 528i |
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08-22-2006, 09:40 AM
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Cars & Coffee Killer
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Well, I went for a "spirited" drive today and the electric water pump kicked in when done. I think without the AC condensor and with the alternator in a better place for cooling, the engine bay stays much cooler...
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Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
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09-03-2006, 08:48 PM
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The pump will come on from temperature or after shutting down the engine. It sounds like maybe the post run function is not working, after the spirited drive the coolant was probably hot enough to make it runon high temp.
Lou
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'87 944 na, sold to a friend '89 951, Weltmeister chips, 3mm WG shim, 968 CS sway bars, stock looking engine bay, just turned over 125K miles. I run Redline oil. |
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09-30-2006, 04:06 PM
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Cars & Coffee Killer
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The electric water pump hasn't run at all lately, but the ambient temperature outside hasn't cracked 70º in weeks. When driving, I have to run it for over an hour to barely crack the first temperature mark.
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Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
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09-30-2006, 05:24 PM
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Either your pump is bad or the relay that controls it is bad. The turbocharger jacket has a thermostat on it. Follow th line that comes from the thermostat to the union point, perhaps six inches away. Unplug it and momentarily ground the female end (the part of line that goes away from thermostat). The pump should run for 20 seconds or so. If it does not, I'd disconnect the pump wires and apply 12 V to see if it is ok. If it runs, then its the relay. The pump should run when you shut off the engine regardless of water temperature.
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Lawrence 1986 951 2002 SLK32 AMG 1987 328GTS 2011 528i |
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10-01-2006, 03:20 AM
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Cars & Coffee Killer
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The pump used to run very loud, but I noticed it was actually running quietly for just a few seconds. Should it be quiet?
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Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
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10-06-2006, 08:07 PM
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Mine makes a humming noise. You can hear it with the hood closed. It is not loud. Mine might be easier to hear because my hood has no insulation.
The run should be 20-25 seconds and it should restart with the car off as heat from the exhaust conducts into the turbo - if the exhaust input and output is hot enough.
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Lawrence 1986 951 2002 SLK32 AMG 1987 328GTS 2011 528i |
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10-09-2006, 07:19 AM
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Cars & Coffee Killer
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I don't have hood insulation either. Hmmm....
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Some Porsches long ago...then a wankle... 5 liters of VVT fury now -Chris "There is freedom in risk, just as there is oppression in security." |
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10-09-2006, 04:35 PM
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