If your vehicle is losing coolant and it’s not dripping on the ground, it’s probably going into the engine somewhere. Follow this Real Fix to see how this rough running Audi A4 with a coolant leak was diagnosed.
Vehicle
2004 Audi A4 Avant Quattro 3.0L
Title
P0300, P0303, P0306, Filled Engine Cooling System, Replaced Engine Cylinder Head Gaskets
Complaint
The customer states the engine coolant recovery reservoir had to be filled twice within one week. The customer also states the engine runs rough.
Cause
Examined the engine cooling system and found the engine coolant recovery reservoir was empty. Filled the engine cooling system, used an engine cooling system pressure tester, applied 15 PSI pressure to the engine cooling system to check for engine coolant leakage. With pressure applied found no apparent external engine coolant leaks however the pressure on the engine cooling system lost some pressure. Due to the misfire codes removed the spark plugs, applied 15 PSI pressure to the engine cooling system for an extended period of time and found the pressure dropped considerably. Cranked the engine and found signs of engine coolant in cylinders 3 and 6 indicating cylinder head gasket leakage. Drained the engine coolant, removed the engine cylinder heads and found the cylinder head gaskets were damaged. The results of these tests verified the cylinder head gaskets were faulty.
Correction
Replaced the engine cylinder head gaskets, filled the engine cooling system, cleared codes, performed a road test and verified the vehicle operated properly.