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Thread: Overheating 3.0

  1. #1
    Active Member Two Rings
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    Overheating 3.0

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    I have a 3.0 B6 A4 with an auxiliary water pump that doesn't seem to be kicking on because the car overheats a little after running for 10-15 minutes. I've already tested the pump and it seems to function. I'm going to pull the relay under the ECU and just replace it. What I'm trying to figure out, is what sensor does the pump get signal from? Is it just the CTS or radiator temp sensor? Or is there another sensor I'm missing?

  2. #2
    Veteran Member Four Rings imnuts's Avatar
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    There is only one temperature sensor on the 3.0 A4, but it has two thermocouples in it, one for the cluster, the other for the ECU. What do you mean by "auxillary water pump"? There is only one pump on the 3.0 stock, and it is driven by the timing belt, so it should always be on.
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  3. #3
    Active Member Two Rings
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    From what I've seen, the North American models have a hot country code and come equipped with an after run electric pump, that's mounted down near the oil filter. It only gets a little hot while in traffic, but if I shut it off for more than a few minutes, the coolant gets hotter from the hot soak and the temp gauge is almost pegged when I start it up. It will go back down towards the middle after 10-15 seconds, once the coolant circulates. But if I shut the car off and start it up immediately, the gauge doesn't run hot at all.

  4. #4
    Veteran Member Four Rings imnuts's Avatar
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    The only auxiliary pump I've heard of on VW/Audi vehicles in the B6 era is one that will force coolant through the heater core. I haven't heard of any B6 coming with one from the factory though. The primary pump is driven by the timing belt either way. It's possible that the impeller is loose on the shaft, preventing it from circulating coolant properly though. Does the fan at the front come on once the car starts hearing up?

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  5. #5
    Active Member Two Rings
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    I just replaced the timing set, water pump, and thermostat, because of this issue. They don't show a picture on ECS , but here is the pump http://www.ecstuning.com/Audi-B6_A4-...Pump/ES280265/ (you can google the part # to see the pump). And also this http://www.audiworld.com/forums/a6-s...-pump-2855598/ . I've tried replacing the relay with no luck. The CTS seems to be fine, because I don't get a check engine, and the fan and gauges work correctly. I've bleed the car a bunch of times, step by step from the manual. The coolant auxiliary pump not running seems to be the only thing it could be coming from.

  6. #6
    Veteran Member Four Rings imnuts's Avatar
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    I can't find any part diagram that lists the auxiliary water pump in the A4, nor have I ever seen it mentioned anywhere before.

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  7. #7
    Veteran Member Four Rings SJorge3442's Avatar
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    I know im late here, but here is a picture of the pump



    I personally ever heard of this pump, not do I know why its needed or how it works. Anyway, I would first change the coolant temp gauge with an OEM audi gauge. Then go from there. These gauges dont always throw a CEL when they go bad but they do cause erratic behavior of the temp gauge. Have you pulled any VCDS metrics such as the coolant temperature? You cant always trust the temperature gauge to be accurate.
    2003 3.0 6 Speed - Quattro. 157k.

  8. #8
    Veteran Member Three Rings john_gonzo's Avatar
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    I'm even later.

    Item #40, Audi PN 06C121601. On those 3.0's without the "hot country" pump, hose #7 connects the oil intercooler directly to the block.


  9. #9
    Veteran Member Four Rings imnuts's Avatar
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    What powers the auxiliary pump? I'm wondering if using one of these would help avoid water bubble issues in the cooling system, and how much of a PITA it would be to retrofit one.
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  10. #10
    Veteran Member Three Rings john_gonzo's Avatar
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    Quote Originally Posted by imnuts View Post
    What powers the auxiliary pump? I'm wondering if using one of these would help avoid water bubble issues in the cooling system, and how much of a PITA it would be to retrofit one.
    I don't know what drives this pump. I did a brief search for info on this system but didn't find much.

    Does "water bubbles" equal air bubbles? If so, I do not think the pump would solve that problem. I can think of only three causes for air bubbles in the cooling system:
    1. Air was already there. Needs to be bled.
    2. Head gasket leak between cylinder and coolant passage (combustion gasses forced into cooling system).
    3. Boiling coolant. (Caused by incorrect water/coolant mix or plugged radiator or thermostat stuck closed or...)

  11. #11
    Veteran Member Four Rings imnuts's Avatar
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    Yeah, air bubbles. I was thinking more for when doing a coolant flush for something like a timing belt service. Not that the pump would magically solve everything, but I would imagine that it would increase the re-circulation flow rate within the system, and possibly keep air pockets from getting trapped in places like the heater core. The shop had issues getting all of the air out of my cooling system when I got my timing belt done, maybe the auxiliary pump could have alleviated some of the issues.
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  12. #12
    Veteran Member Three Rings john_gonzo's Avatar
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    Oh yeah, understood.

    When I get some time, I'll dig through the Bentley wiring diagram for this pump and see where it leads.

  13. #13
    Veteran Member Four Rings SJorge3442's Avatar
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    Quote Originally Posted by john_gonzo View Post
    Oh yeah, understood.

    When I get some time, I'll dig through the Bentley wiring diagram for this pump and see where it leads.
    Excited to see what you find! I just learned this past weekend that I do infact have this pump (who knew!) and I'd like to know what triggers it. I would imagine it gets triggered when the coolant/oil temp reaches a certain level and then the coolant begins flowing faster through the secondary cooling circuit. I'm thinking this is related to oil cooling more than anything else due to its proximity to the oil cooler housing and how its linked together.
    2003 3.0 6 Speed - Quattro. 157k.

  14. #14
    Veteran Member Three Rings john_gonzo's Avatar
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    Hey guys, the wiring diagrams don't give the exact trigger conditions for this pump but power to it is through the Coolant Circulation Pump Relay (J151) which is switched by the Engine Control Module (ECM). Both located driver's side, base of windshield.

  15. #15
    Veteran Member Four Rings SJorge3442's Avatar
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    Quote Originally Posted by john_gonzo View Post
    Hey guys, the wiring diagrams don't give the exact trigger conditions for this pump but power to it is through the Coolant Circulation Pump Relay (J151) which is switched by the Engine Control Module (ECM). Both located driver's side, base of windshield.
    Thanks for the update. I was actually browsing through a parts diagram site recently and found a section that claimed this pump was only included on warm weather climate engines.

    Since the 3.0 innately runs hot, I would be willing to bet(maybe) that this pump is always running once the car is up to temp. It's strange that we never see people replacing this. My 3.0 runs hot, like 220 degrees all the time. I wonder if my AUX pump is no longer working....

    Thoughts?

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    2003 3.0 6 Speed - Quattro. 157k.

  16. #16
    Active Member One Ring
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    IM thinking that this aux electrical water pump (which I have also) is controlled by the ECM and yes it's controlling the volume of water which is directed to the oil cooler to cool the engine oil temperatures... This signal I believe is emanating from the oil sensor device, which is mounted in the lower oil pan



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