There's your problem - the cylinder head is cracked!
29 July 2020
The above comment is heard far too often when referring to a vehicles over-heating problems. But in reality this is not the "Real Problem" at all.
Cylinder heads mainly crack for one reason only... it got too hot first, then it cracked when it cooled. The head cracking is the "result" and not the "cause" of the problem. So first the "real problem" needs to be correctly diagnosed to successfully complete the repair job.
So what is the real reason then? Modern engines are becoming more and more sophisticated, to be able to meet the demands on our environment and our pockets with lower fuel usage. In respect to modern diesel engines the areas that have been developed to help in these areas are the fuel delivery and combustion processes. With much higher fuel pressures (upwards of 18-20,000 psi) found in modern common-rail technology, these pressures have a spin off of increased fuel temperatures being returned to the fuel tank. This leads to the possibility of condensation forming in the fuel tank once the fuel cools. Most of us will know that water in the fuel is not a preferred option, and hopefully the fuel filter system will help to manage this contamination of the fuel. But even the best-designed and manufactured systems will fail if the maintenance of the system is not kept current. Once a fuel delivery system is compromised and contaminated a chain of events follows which can lead to costly repair bills for the owner. This is referred to as "Improper fuel delivery" This term can relate to any part of the fuel system, e.g. injectors, pumps, filters etc. When this happens another phenomenon occurs, "Abnormal Combustion" this leads to greatly increased cylinder temperatures which of coarse can lead to failed gaskets and engine components. Fuel system compromises are not just limited to high fuel temperatures only; poor fuel quality is a real issue as well. Great care should be taken to limit the presence of sub-standard fuel being used, but that is an entirely new discussion.
The other main area of concern is the cooling system. This isn't just the radiator, water pump and hoses either. The entire cooling system has to be taken into account. Viscous and thermo electric fans, heater cores and badly contaminated cooling systems are all to be considered and inspected. A badly contaminated system will only re-block a new radiator and damage the new water pump as well. Then the original fault re-appears.
Summary... "The obvious fault may not be the real fault... look further"