# Something still running under the hood after being shut off?



## crazyaboutrocs (Nov 23, 2005)

Ok, I'll make this short and sweet. My sister purchased an '02 TT this summer. She just called to say that it has been making a "noise" under the hood, on the right side near the radiator. She says it sounds like something running(maybe some sort of a pump) right after shut down, but started doing it ALL the time. Now the battery is dead, most likely as a result of this. I've been working on my own VWs for over twenty years, but this TT is a whole different animal. I do have a MkV GTI and have a manual for it, so if some of the underhood stuff is the same maybe I can ID it. But it would be best if I had an idea of what this thing is before I go look at her car. Any thoughts?


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## crazyaboutrocs (Nov 23, 2005)

So I was just checking GAP's site and noticed an "auxiliary water pump." Sounds like this could be the culprit, so I will start there. What controls this pump? And for my knowledge, why does it have this?


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## Mantvis (Jan 1, 2010)

auxilary water pump it is, its right by the radiator fan.

The aux water pump is for heating the cabin after the engine is shut off. It circulates the still-hot coolant so that the heater core will stay hot and provide heat to the cabin.
also aux water pump is to ensure that under all engine RPM the same amount of hot water is pumped into the heater core, no matter if engine is at idle or high RPM. Capacity 950 l/H. This ensures that always the same temp is there, on other cars without aux water pump the volume of hot coolant into the heater core depends on the RPM of the engine = idle, it gets cooler, because the main water pump is driven via a belt, the aux water pump electric.
You can bypass the aux water pump of course, many have done it to save the $120 or so.
But I like it especially in cold winter. The aux water pump starts when coolant has 30 degreeC.


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## crazyaboutrocs (Nov 23, 2005)

Thank you, that was nowhere near what I was thinking it might be for(reducing heat in engine due to the turbo or some such thing). So where would I find what is controlling this pump? It seems that it wouldn't be the pump, but it's controller. In the end, I will leave it up to my sister as she will not drive it in the winter.


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## J Patterson (Apr 11, 2009)

*225 hp TTs have the after run coolant pump. 180s do not.*

It's purpose is to cool the turbocharger bearing after the engine is shut down. It is turned on and off by the fan control module. It should run for a few minutes after the ignition is turned on and back off even with a cool engine. Fan control modules are troublesome and coause lots of odd cooling fan issues. This is the first time I have heard of an after run coolant pump running continuously though. I would just unplug it till I replaced the fan control module. It will not hurt the turbo as long as you don't do shut downs immediately after a hard run.
Good Luck !


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## VelveTTrevolvr (Jul 31, 2009)

Mantvis said:


> auxilary water pump it is, its right by the radiator fan.
> 
> The aux water pump is for heating the cabin after the engine is shut off. It circulates the still-hot coolant so that the heater core will stay hot and provide heat to the cabin.
> also aux water pump is to ensure that under all engine RPM the same amount of hot water is pumped into the heater core, no matter if engine is at idle or high RPM. Capacity 950 l/H. This ensures that always the same temp is there, on other cars without aux water pump the volume of hot coolant into the heater core depends on the RPM of the engine = idle, it gets cooler, because the main water pump is driven via a belt, the aux water pump electric.
> ...


:what:

Hahahaha!


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## InTTruder (Mar 28, 2006)

The aux pump circulates coolant to/from the turbo on the later cars. It does NOT warm the cabin.:facepalm:


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## Doooglasss (Aug 28, 2009)

crazyaboutrocs said:


> Thank you, that was nowhere near what I was thinking it might be for(reducing heat in engine due to the turbo or some such thing). So where would I find what is controlling this pump? It seems that it wouldn't be the pump, but it's controller. In the end, I will leave it up to my sister as she will not drive it in the winter.



So as others have said the after-run coolant pump is to circulate coolant through the hot turbocharger to cool it down after driving. The pump runs for about 10 minutes after the car turns off I believe. To answer your question this is *not* the source of her power drain issue. How old is her car's battery?


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## crazyaboutrocs (Nov 23, 2005)

Thanks to everyone about circulating water through the turbo after shutting it down. I spoke to her today about it and told her to unplug it for now and recharge battery. Sisters.....:banghead: She said it had been doing it a while, as in come out the next morning and it was still pumping(she and bf put hand on it so they knew that whatever it was, was still going). She could've told me sooner, but that's what sisters that don't know crap about cars do. Only reason the battery went dead is that she didn't drive it all week.:facepalm:


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## Mantvis (Jan 1, 2010)

Mantvis said:


> auxilary water pump it is, its right by the radiator fan.
> 
> The aux water pump is for heating the cabin after the engine is shut off. It circulates the still-hot coolant so that the heater core will stay hot and provide heat to the cabin.
> also aux water pump is to ensure that under all engine RPM the same amount of hot water is pumped into the heater core, no matter if engine is at idle or high RPM. Capacity 950 l/H. This ensures that always the same temp is there, on other cars without aux water pump the volume of hot coolant into the heater core depends on the RPM of the engine = idle, it gets cooler, because the main water pump is driven via a belt, the aux water pump electric.
> ...


Thats what you get when you just copy and paste info from a BMW forum... :facepalm:


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## crazyaboutrocs (Nov 23, 2005)

Well at two of us learned something yesterday. Not a bad thing.


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## TTMAN225 (Jan 20, 2005)

Mantvis said:


> Thats what you get when you just copy and paste info from a BMW forum... :facepalm:


HA, be honest, you were going to run with it like it was your thought had it been right hahaha

which one is the forum cred fail emoticon? :wave:


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## Mantvis (Jan 1, 2010)

most of people would of known that its not my thought im wayy to young


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