Engine Management Light on Engine overheating

4.2 V8 40v biturbo - 450 bhp
4.2 V8 40v biturbo - 480 bhp (plus)
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RS6Rottweiler
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Engine Management Light on Engine overheating

Post by RS6Rottweiler » Wed May 17, 2023 9:43 pm

The engine management light has come on in my car, but initial indications were that the engine was running okay and was running well. I stopped the engine and I noticed that the main radiator fan was running flat out but the engine wasn't overheating initially. I later noticed when I ran the car that the engine was overheating with temperature above the 90 degree normal running temperature. I connected Vagcom but it didn't show up any fault codes associated with the engine management. I tried to do a check on Address 1 (Engine) but it stated there was a problem connecting to the controller so I couldn't carryout the check. I appreciate that this may be two different issues or it could be that I'm not that great using Vagcom. My initial thoughts were that the coolant pump may have failed but there could be something else potentially stopping the cooling water circulating around the engine. When I drove it, the engine temperature sat around 90 degrees for a while then rapidly increased, when I stopped the engine, the radiator fan again was running flat out. I struggle how the engine is overheating with the fan running flat out so my thoughts are either pump or a solenoid or something not opening preventing the coolant from circulate, but why has the engine management light come on? I would appreciate if anyone has any ideas on what could be wrong or experienced something similar. Likewise, is there anther fault preventing Vagcom checking out the engine Address 1 (Engine) and reading the engine fault codes, or is it operator error. Any help I can get with this would be greatly appreciated, thank you.

Felix2566
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Re: Engine Management Light on Engine overheating

Post by Felix2566 » Wed May 17, 2023 11:24 pm

My first thought would be to check if the thermostat is opening. When the fans are running is the top radiator hose/top of the radiator hot too? If it isnt the thermostat most likely isnt opening and allowing hot water to circulate through the radiator. Be careful about running the engine too long if it is over heating.

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Shoppinit
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Re: Engine Management Light on Engine overheating

Post by Shoppinit » Thu May 18, 2023 7:39 am

There are no solenoids or switches in the coolant system. As above, most likely is the thermostat, but it could be the coolant pump or a blown head gasket.

Hard to say what the MIL is for if you can't plug the Vagcom in. Might be something related to the overheating.

The temperature gauge on the dash is next to useless. It stays pinned to 90 unless the coolant temp goes well out of bounds.

You need to get the Vagcom working. Is it a genuine one?
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

RS6Rottweiler
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Re: Engine Management Light on Engine overheating

Post by RS6Rottweiler » Thu May 18, 2023 1:02 pm

Vagcom is genuine but for some reason it won’t connect to Address 1 or 2. I’ll contact them for assistance and see if they’ll come up with a solution to the Vagcom. My initial thoughts are just to replace the pump and thermostat. I don’t suspect a blown head gasket as the engine was running smoothly but I’ll check it out. Thanks for your help, any other ideas are always welcome. Thanks

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Shoppinit
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Re: Engine Management Light on Engine overheating

Post by Shoppinit » Thu May 18, 2023 1:32 pm

Have you tried an auto scan?
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

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Shoppinit
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Re: Engine Management Light on Engine overheating

Post by Shoppinit » Thu May 18, 2023 1:33 pm

You can also display the coolant temp on the heater controls. See the FAQ to see how.
Daytona RS6 C5 Avant. Viper'd, Billies, Waggers, MTM box brain, C6 stoppers, xcarlink, R8 coolant cap (woohoo)
///M3 E46 | XC90 (V8, natch) | Passat GTE | RR Classic V8 flapper
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair."

Mɐʇʇ
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Re: Engine Management Light on Engine overheating

Post by Mɐʇʇ » Thu May 18, 2023 5:30 pm

This. If it's even a tiny whisker above 90, stop immediately.
Shoppinit wrote:
Thu May 18, 2023 7:39 am
The temperature gauge on the dash is next to useless. It stays pinned to 90 unless the coolant temp goes well out of bounds.
"not a professional engineer, mechanic and mechanist"

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