The owner of this Discovery 3.0 TDV6 had a complaint of excess smoke from the exhausts.
We stripped down the air box and first of all carried out a leak test, we found no leaks but what we did find was oil in the air box.
The turbos use oil for lubrication and it is normal to find some oil in the intake pipes but to have this much we knew it was being pushed back.
As this engine has a sequential twin turbo set-up the small turbo kicks in first and then the larger turbo. What was happening was the Turbo Control Valve switching the boost over wasn’t functioning correctly. This caused boost pressure to leak and force oil back to the airbox.
The engine now runs perfectly, with no excess smoke from the exhaust