WWDiesel wrote:
TURBO-DIESEL-FREAK wrote:
Better exhaust valves are always a good idea, but this will likely not solve the problem of exhaust valve breakage if the problem does not lie with the O.E. exhaust valves.
If you have any proof of this, PLEASE share it with everyone!Excerpt from the Report on Valve Failures: wrote:
"Although ~3E8 cycles to failure is a relatively short life for this application, high cycle fatigue was concluded to be a possible mechanism of failure. A future inspection of the exhaust gas recirculation (EGR) equipment may provide further evidence for the cause of this shortened valve life."
Exhaust valve heads snapping off (breaking) certainly speaks loud volumes and provides us with the
single point of failure mechanism for engine catastrophic failures while although the absolute "Root Cause" may not be 100% crystal clear, the end result certainly is. It has been a well established fact for some time that when an exhaust valve failure does occur on this engine, it usually happens on higher mileage engines due to the high-cycle fatigue regardless of any whys.
The Bottom Line: IF there is
anyway to help prevent these valve failures, many owners would be more than willing to invest in an improved metal composition valve like the *Inconel valves to extend the life of their diesel engine without worry of future and imminent catastrophic failures. Heck, we have enough other issues to worry about without this one!
Quote:
*Inconel valves are made from a Nimonic 751 alloy which has better resistance to heat (and abrasion) than stainless steel. Inconel valves are only used for exhaust valves, as it is the only side that it is needed to use a higher temperature alloy. INCONEL valves can withstand an operating temperature of 1,600 F (approx 2200 F EGT). Inconel Valves are the highest quality material available for diesel exhaust valves, they are used in many applications as direct replacements for factory valves especially on higher output engines or where there is a history of early valve failures.
WWDiesel:
The point I clearly made - and one that you seem to overlook - is that the CRD "experts" are focusing in on the quality of the exhaust valves ALONE, WITHOUT REGARD TO ANY OTHER FACTOR that could cause or contribute to exhaust valve failure. This is a mistake, and one that should not be made by someone who is truly trying to deduce the real reason or reasons why this problem is occurring. Focusing on one possible culprit while ignoring other possibilities opens the investigator up to accusations of spin doctoring. Democrats, Liberals and Leftists are world class experts in this tactic... the whole issue of Climate Change has spin-doctoring written all over it. Please avoid this if you want to be taken seriously.
You said it yourself that the metallurgical study was inconclusive; your precise words were "While the root cause of the broken valves has never been 100% ascertained...". You asked for "proof", and yet you provide little of it yourself to make the case that the quality of the exhaust valves are the sole reason for exhaust failures. Seeing as it is unlikely any of us will have the money to thoroughly research this with the CRD engine, we are left with sussing out the problem by looking at the most common reasons why exhaust valves fail in all internal combustion engines, and why exhaust valves fail in turbo-diesel engines that have aluminum cylinder heads in particular.
More to the point, has ANYONE actually done any continuous measuring of exhaust temperatures in CRD engines? This would go a long way to determining if the exhaust temperatures are high enough to lead to exhaust valve erosion issues. REMEMBER that exhaust gas temperatures do not directly correspond to the same temperatures in the valves themselves.... some cooling does indeed occur as the exhaust valve meets the seat
Cylinder head warpage also occurs more frequently as the miles pile up. In the article I posted a link to above, the following is written... "Fatigue from the valve flexing due to being off-center on the seat can also cause failure." The chief cause of an exhaust valve being off-center is from warpage.
All that I am trying to communicate here is to look at ALL the reasons why exhaust valves are failing in Jeep Liberty CRD engines, not just the quality of the valves themselves.