The vehicle came into our workshop with 2 problems. The first problem was cooling system pressurisation, the second issue was uneven running and smoking on cold start up.
To determine what the problem was regarding the engine cooling problem, the cylinder heads were removed and pressure tested. The test revealed that one cylinder head was cracked in an unusual place which was in the combustion swirl chamber. When the VM cylinder head cracks in this place, they are not usually repairable so in this case a new cylinder head is fitted to that cylinder. The other 5 cylinder heads were also pressure tested, checked for flatness and the valves and seats were re-cut. At the same time the wet cylinder liners were checked for porocity. Upon re-assembly we established that the cooling system was no longer pressurising so the issue was resolved.
Regarding the cold starting problem, checks were made and we discovered that the cold start advance mechanism was fluctuating between the normal running position and what appeared to be a significant advanced timing situation. This also created varying noise levels between sounding very ‘diesel knocking’ and a very quiet running engine with no diesel knock. When the engine was in the quiet running mode (fuel timing retarded), the engine produced large amounts of white/blue smoke.
All the usual checks were made on the electronics that determines the positioning of the cold start. Eventually it was traced to a faulty fuel injection sensor. This was duly replaced and the problem solved.