Coolant Temp Sensor unplugged = starts fine. I've been having issues with starting the engine (BRD 170 TDI) over the last few months, I had thought it was the battery at 1st and swapped that and all was well for a few weeks but the problem returned. Sometimes it takes about 3 - 6 attempts to turn over after turning the key, Other times it will Step 2 - Connect Digital Volt-Ohm Meter. Testing the coolant temperature sensor is a very quick process. With the use of a digital volt-ohm meter you can easily tell if the sensor is faulty or not. Connect the black lead of the digital ohm meter to a solid grounding. This can be any solid piece of metal. Most drivers don't care what the coolant temperature is, just whether or not it is overheatingI expect soon the gauge will be removed altogether and just the overheat light left with the variable redline tach to indicate when the car is "warmed up". FWIW Q5 3.0T spec is "Opening begins" at 87ºC (189ºF) and fully open at 102ºC (216ºF Guest-only advertisement. Register or Log In now! A few weeks ago I noticed a small puddle and trail of coolant leaking from beneath my 2005 A4 3.0. I took it into a local indy shop who pressure tested the system and found that the coolant temperature sensor was leaking, so it was replaced. A few days later I discovered coolant dripping again Audi Mechanic: Eric. Hi Michael! There are 4 exhaust gas temperature sensors - SEE ATTACHED LOCATION DIAGRAM. The brake vacuum booster is tucked in at the firewall on the driver side of the engine compartment underneath the cowl and plenum chamber and is right at 4 hours to replace. See attached. gwtA.