Fumé blanche 407 coupé v6 (2.7L HDI)

Here's a recurring problem on the 2.7L HDI (V6 PSA) engine fitted to the 407 Coupé V6. The symptoms are typical of a blown head gasket, but it's not. The garage quoted €5500, but the diagnosis was wrong. For your information, a blown head gasket causes overheating, water in the oil (mayonnaise-like substance), and significant starting difficulties most of the time... Symptoms: thick white smoke, coolant leak, engine jerking, and water coming out of the exhaust. NO NEED TO REMOVE THE ENGINE!!! It's true, it's very tight, but quite easy to do. Three-quarters of it is done from the top. From the bottom, you just have to unclip the clamps on the two exhaust hoses to get your hand in. That's all. Bowden cable pliers are highly recommended... (for the ear clamps on the coolant hoses) The EGR cooler is leaking from the inside, allowing coolant to leak out and come into contact with exhaust gases, so a CO2 test will inevitably be positive. A coolant pressure test will also be positive, but be aware that this isn't necessarily a head gasket issue (at least not necessarily...).