| Coolant Sensor Failure may kill your car! - WRONG!! | |
My Audi A4 Cabriolet 3.0 V6 (2004) has been a reliable old soul and has started first time everytime for 7 years.
Not so on returning from the shops on Saturday. Wife parked up on drive to empty bags etc., then went back to park neatly. Not starting. Oh I said (thinking left in Drive instead of Park + other things!). Had a go myself, not starting, turning over though. Leave it for a while I thought. Went back 1/2 an hour later, car started then died. Hmmm...fuel ? Left it overnight.
Nice cold engine, turned over, refused to start.
Out with the VCDS:
ENGINE:
1 Fault Found:
19497 - Powertrain Databus
P3041 - 004 - Implausible Engine Temp. Message from Inst. Panel - Intermittent
INSTRUMENTS:
1 Fault Found:
01039 - Coolant Temperature Sensor (G2)
30-10 - Open or Short to Plus - Intermittent
Surely this wouldn't stop the car from starting? Googled way, checked with Ross-Tech Wiki. No-one saying they had a non-starter, just rough running or difficulty in starting. one chap on an Audi forum said he just disconnected his sensor, and car started OK. So I thought I would try this first.
Now where is the coolant sensor on an Audi V6 engine in a Cabriolet? You guessed it tucked away on the back coolant rail near the bulkhead and below the intake manifold. Any room to get at it? Like heck. Can you easily see it, like heck!
After dismantling parts of the air intake and moving several wires and tubes I could squeeze my left hand in behind the engine and get to the sensor (good job am left handed and small hands/arms). But with a torch and a long thin screwdriver I was able to see to release the clip on the wiring connector. Stupid things. Put air intake stuff back together and tried to start. Turned over but no startie, however this time cooling fans fired up to full speed! Oops.
This is caused by the circuit being open. Reading up, even a paperclip across the pins would cause the opposite (too cold). So like Goldilocks' porridge, the reading has to be "just right". Still didn't think it was the coolant sensor though...
That evening did a click and collect with europarts for a coolant sensor on the basis that if VCDS says it is broken it needs fixing, and having found a guy in the USA on youtube who had a non-starting Ford Taurus that was fixed with a new coolant sensor. Nice drive to Soton in the rain on Monday morning, new sensor came without an O ring so that was another £1.39!
Back home made a start, air intake stuff off again, tubes and wires moved aside, then fiddled about with short screwdrivers releasing the plastic spring clip that holds the sensor in place, its passage blocked by the coilpack wiring. Remember, this is one handed, with a viewpoint not much more than looking down a straw! Spring clip finally off. Wobble the sensor, out it came, along with 2 pints of coolant (damn, forgot to depressurize!). O ring stayed in so fabricated a hook thing from a large paper clip to hoyk it out.
After all that new one went back in a bit more easily, and topped up the coolant. Would it start, heck it wouldn't! But the fans came on again. (Clue - but was not as quick as Sherlock's sister!)
Decided to check fuel/fuel pump - really useful section in ElsaWin on testing fuel pump. Fuel pump fuse OK, Fuel pump relay OK. Fuel pump works.
Decided to check things out with VCDS again. This time VCDS told me I had "16502/P0118/000280 - Engine Coolant Temperature Sensor (G62): Signal too High". Cleared codes, turned the key, engine started. 
Morale of the tale: don't give up, sometimes it is worth believing what is there in front of you.  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962
Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999
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16th Jan 2017 3:40pm
A right fiddle refitting the suction jet pump to the main pump as you have to do this in tank.
