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[teamroper60]

Originally Posted by outlawpony

i am a for diesel tech i have an 04 6.0 i welded my valve shut if you think of it like blowing in to a bottle if the valve is shut and not flowing the gas will not flow through the cooler and too much flow from the egr valve is what ford is relating the egr cooler failers to due to the statige from the iat2 sensor the check engine will not come on due to this but po401 and po404 will be stored in the pcm ford master tech and deisel tech

Low coolant flow through the cooler (generally caused by a plugged oil cooler), allowing the coolant to superheat is what is causing the EGR cooler related puking and, ultimately, the cooler failures.

The cooler is made out of metal and can only accept so much volume of exhaust gas into it. So, while it is entirely possible to have a valve stick open and send excess EGR gases into the engine, it is not possible for there to be too much flow through the cooler itself. Blocking the flow of exhaust gases going through the cooler will allow the coolant to wick some of the heat out of the cooler, but that heat will only be marginally reduced due to the heat soak from the exhaust gases that are attempting to get in.

Along that same vein, your analogy of blowing into the bottle got me to thinking.... If you blow into a plastic soda bottle, it will attempt to expand due to increased pressure. Obviously, it can only expand so much, since the plastic itself only has so much "give" to it. Enough pressure on that bottle (probably more than the average person could provide, but not more than an air compressor could, for instance) and the bottle ruptures. The same phenomenon may well apply to the EGR cooler... Gases would be trying to get in but would be blocked by the closed valve, raising the pressure inside the cooler.. I don't know if the engine could provide enough pressure to rupture the cooler, but as we know, heat has a tendency to weaken metal and in addition to the exhaust heat, pressure also creates heat (the very principle upon which a diesel engine operates). So it may be possible that over time, the cooler could fail from this combination of heat and pressure.....

Again, that is just something that occurred to me. Since I don't know the stress failure point of the components that make up the cooler or the amount of pressure being applied to the cooler by the exhaust gases, I have nothing concrete to back that up.