Waiting on side of road for assistance.

Car was vagcom last weekend without any error codes. However, over heated error icon just appeared and power has been cut to engine.

Coolant levels are normal so what other factors could cause car to overheat? Faulty water pump or sensors?

Thanks
J

 

I know this is the Audi W12, but lets face it they are pretty similar sans the turbos. Page 22 has an overview of the cooling circuits. It may not be anything, I have seen situations (with my D3 A8) where the expansion tank allows the coolant to back flow into the tank and it sends the temp sensor through the roof. Coolant temps are fine but the valve in the expansion tank gives the sensor a false reading. Your situation could be different, but its something I saw once before and I had zero fault codes.

http://www.audiklub.org/data/files/W12D3L.pdf

 

Thanks for reply arpad.

Confirmed faulty exhaust bank 1 temp sensor. However, replaced same sensor back in 2012 and was told they can die if car is not driven enough.

Anyone else replaced this sensor? Car is not a DD and driven probably 4 times a month.

Thanks

 

I had to replace the exhaust manifold temperature sensor on Bank 2 at 47K miles. It threw P0546 error but didn't cause the car to stop. I believe the sensor's function is to detect high heat conditions leading to catalytic converter failure. While we were able to confirm the sensor was indeed faulty, I also had a pre-cat failure on the same bank.

 

The replaced temp sensor done at dealer has less than 5,000km on it.

What could kill the sensor so quick?

Thanks

 

I am certainly no authority on the subject. As I understand it, the exhaust manifold temperature sensor is a relatively straightforward thermocoupler device composed of two different metal alloy wires. Combining two different metals generates a strong voltage that has the same capacity as temperature.

I found this interesting note: "The EGT probe is subject to an extremely violent high temperature / high pressure environment. Over time it could be possible for an EGT probe to degrade and potentially send fragments into the exhaust system and turbo charger. The tip of the EGT probe is designed to slowly burn away and EGT probes normally quit working before degrading to a dangerous point."

If I had to guess and, assuming it was correctly installed,I would say you possibly got a sub-standard EMTS 5000 Kms ago.

Further explanation will require the expertise of forum members BentleyTech or Bentley Tech NY. Maybe they will jump in?

 

Hi PMS

I think your description are for lambda sensors but I could be wrong, uploaded photo of concerned part.

I am not familiar with EGT sensor which has a small circuit board as the fault code I received was "G235 circuit malfunction". Indeed quite a sub-standard part from the dealer but being nearly two years ago and I doubt they will warranty any claim so installing another at independent workshop.

Whilst at workshop also getting coolant and brake fluid replaced but holding back on spark plugs. I found out all pre MY07 cars used NGK PFR6Q (0.8mm gap) and after were NGK PZFR6Q-11 (1.1mm gap). Has anyone switched to the 1.1mm or other plugs and notice any difference as the larger gap produces a larger spark to maximise burn efficiency.

Thanks

 

I remember in the 2006 GT pre-40k spark service she felt good, yet after the 40k service she did seem to have a bit more oomph. Of course they also changed the spark coils, as those are a known problem on early models. Frankly, not sure if it really made a difference, yet she felt very strong afterwards right up until it was traded for the 07 GTC.

 

The part I replaced was the exhaust gas temperature sensor (3W0971963E) (bank 2). I believe you replaced the sensor on bank one (1J0973703). These sensors measure temperature (unlike the O2 sensors) which measure the O2 delta ahead and behind the pre-cat. Unlike the error code I got which pointed to the sensor itself, your code points to the circuit board that reads/interprets the sensor. In the end, we both had to replace the assembly but perhaps for different reasons.

re: plugs. I have included the chart showing the factory recommended settings for gap. (for your application 0.7 gap). For your possible interest, I changed the ignition coils at the same time I changed the plugs (45K miles) with original PFR6Q. I Didn't feel much if any difference and fuel economy was the same.

 

Car still at workshop so had intermittent faulty rear parking sensor replaced.

 

i know this tread is old but i thought I'd shed some light. the bank 1 EGT actually shares a circuit with one of the coolant sensors. so when it decides to freak out it also alters the coolant signal which then makes the vehicle think its overheating. usually the DIP will tell you its overheating but the temp gauge is in the normal range when this happens.

 

Good to know.

Sensor was replaced and car is up and running again.