OIL CONSUMPTION

COMMON CONCERNS: Adding Oil Between Services, Blue Smoke When The Engine First Starts, A Falling Level With No Stain On The Floor.

The oil light comes on a couple thousand miles after a change, with no drop on the garage floor. This one belongs to the 2011 and 2012 Q5 with the 2.0-liter turbo, because Audi revised the pistons partway through that run. Oil slips past the rings that seal the piston and burns in the cylinder.

When the smoke shows up is the question we open with. A blue puff at the first start after a night parked comes from oil that seeped past the valve guides. A haze that builds on a long climb with the throttle open points at the rings. We top the oil, mark the level, and set a measured interval for a number you can work from.

COLD-START RATTLE AT THE TIMING CHAIN

COMMON CONCERNS: A Diesel Sound At The First Start, A Rattle That Lasts Longer Than It Used To, A Timing Warning Light.

How long the rattle lasts is the number we want. On the 2011 and 2012 2.0-liter turbo, the part that keeps the timing chain tight works on spring force until oil pressure comes up. That spring loses tension with age, so the noise runs longer each year.

That makes the appointment part of the test. A car warmed up in our lot stays silent, so we book these first and start it cold ourselves. One second of rattle is one reading, and four seconds on a car that used to rattle for one is another. We also scan for the codes set when the two ends of the chain fall out of step, and that much slack can slip a tooth.

WATER PUMP AND THERMOSTAT

COMMON CONCERNS: Coolant Under The Car Overnight, A Low-Coolant Warning, Cabin Heat That Stays Weak.

On the 2011 to 2017 Q5 2.0-liter turbo, one plastic assembly carries the water pump and thermostat, and it can fail in two very different ways. The housing goes brittle and a seam cracks, so coolant collects under the car and the low-coolant light comes on. Or nothing leaks at all, the thermostat holds open toward cold, and the engine never reaches its normal temperature.

A dry floor is what separates the two, so the heater is where we start. We record coolant temperature from a cold start through a full warm-up and watch for a reading that stops short of normal. That short reading is the weak cabin heat you noticed. When the floor is wet, we hold the cold system at pressure and follow the loss to the seam.

CRANKCASE BREATHER AND VALVE COVER

COMMON CONCERNS: A Rough Or Hunting Idle, A Whistle From The Top Of The Engine, Oil Use With No Puddle.

With the engine running, try to lift the oil filler cap off in your own driveway. A cap that won't come up easily points at the vent system on top of the engine. Pressure builds inside the crankcase and vents through a valve built into the valve cover. Inside that valve sits a thin rubber diaphragm.

When that diaphragm tears, air slips in through the opening without being measured. The idle turns rough, and oil vapor gets pulled into the intake. A torn diaphragm and worn rings produce the same falling oil level. The cover gets checked before anyone opens the engine. We smoke-test the intake to find the opening, and the fuel data shows the extra air. The repair depends on the exact engine and part number, because some Q5s use a separately serviced vent valve and others require the full cover assembly.

BRAKE PADS, ROTORS AND THE WEAR SENSOR

COMMON CONCERNS: A Brake Warning On The Dash With No Noise, A Ridge At The Edge Of The Rotor, Heavy Brake Dust On The Wheels.

A Q5 carries more weight than the sedan it shares an engine with, and all four wheels drive it, so every stop makes heat at the pads and rotors. Audi builds the warning into a thin wire in the pad rather than a metal tab that squeals. The pad wears down to that wire, the wire breaks, and the warning appears on the dash before you hear a sound.

We pull the wheels, measure what is left of the pad, and check the rotor against Audi's minimum. A broken sensor wire and a worn set light the same warning, so we measure to tell them apart. We read those numbers first, then say whether it is pads alone or pads and rotors.