Blown Gasket Cure
Ihave changed a fair few head gaskets on 200Tdi engines over the years, almost always because they have failed between number four cylinder and number eight pushrod tube. I have also seen a couple fail at the very back of the head. In my experience it is far less common for them to fail in such a way as to affect the cooling system: there is ample material around all the water passages, and plenty of large, strong head bolts to keep everything sealed up. Most gasket problems on these engines seem to develop around the edges. There are however exceptions to every rule. I had a Defender 200Tdi come in which was dumping engine oil into the cooling system. The owner’s first thought had been a split in the oil cooler, which is located inside the radiator. A new radiator had failed to solve the problem, so the vehicle came to me for further investigation.
The old 19J turbodiesel that preceded the 200Tdi had a nasty tendency to develop internal cracks within the cylinder block which would cause exactly this symptom (a coolant header tank with a layer of black oil floating on the top of the coolant). The 200Tdi cylinder block is a progressive development of the 19J, strengthened in various ways, but I was still worried that a cracked block might be the cause. There is only one pressurised oilway between the head and the block, and it is an awfully long way from any water passages. But before condemning the engine I decided (with the customer’s agreement) to lift the cylinder head. What I found was an oily mess, with oil under pressure radiating out in every direction from the oil way.
I am still not entirely sure how the oil was ending up in the coolant. I suspect it was migrating along two different bolt threads under pressure and being fed into the cooling system via the water pump. In any case I had the head skimmed and pressure tested and all seemed fine, so the engine went back together with a couple of new steel locating dowels as the old ones had cracked through (which may have been the root cause of the head gasket failure). The owner told me that the head gasket had been replaced 14 years previously. Hopefully it will last at least as long this time round.