I recently purchased an 87 300 TD Turbo. 260k. It smoked (white) when cold start and a bit more under heavy acceleration,etc. I started running B100 biodiesel, changed the air and fuel filters and now it only smokes (white) on cold start and a bit during heavy loads, etc. I noticed a strong exhaust smell with the windows up and stuck rags in the tailpipe to find a leak. I can't find any leak, but can smell exhaust under the hood. When I search the threads indicate the flexible exhaust piping can leak, and that white smoke means water / coolant. There is diesel staining on the firewall on the exhaust manifold (driver's right) side. Most staining right around the back of the head, not near the flexible sections of exhaust pipe.

The oil looks fine and the coolant looks fine and doesn't seem to drop. Could this be a leaking head gasket on the exhaust manifold side. Is there a better way to find the exhaust leak and is it linked to the smoking?

Only have records for the past couple of years, oil changes, a/c charge, nothing major.