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Don't jump to the head gaskets. I suspect that many heads are pulled and studs installed when the only real issue was the coolers. And I'm not sure it is quite accurate to say that the EGR cooler fails because the oil cooler clogs. It seems to start with the EGR cooler where the short distance from the exhaust ports means extreme temperatures, which cooks the coolant ( Ford gold breaks down at those temps, silicates drop out to a gritty sand and goo. Green stuff even worse, a lot worse.) Some of that starts clogging the cooler passages and the rest flows next to the oil cooler and clogs it up. But that's the coolant passages being clogged, not the oil passages.
So now you have gradual clogging of both coolers, which means that the coolant moves more slowly and has more time to cook in the super-hot EGR cooler and not cooling it as much, and reduced flow of hotter water through the oil cooler which makes it less efficient and shows up as higher delta in your temps. But in most cases your radiator and T-stat are able to handle the coolant when it gets there so the problem never shows on your dash gauge.
So far you aren't really hurting the engine if your dash temps are good unless the oil temp gets way high and breaks down. The coolant in the engine is still at the correct temp so the head gaskets are not trying to fail. But eventually the coolant passages in both coolers, like clogged arteries, restrict flow to the point that the EGR cooler gets too hot and cracks or ruptures and spews coolant back into the exhaust. That comes out as sweet white smoke/steam, and exhaust getting into the coolant passages may cause that to boil out the degas tank. Classic symptoms of a head gasket, but not a head gasket, yet.
Ignore the problem and just keep adding coolant is the worst thing you can do because it will get worse and at an accelerated rate. If you lose track and let it get too low, you may overheat the engine and blow a head gasket. Eventually the EGR cooler fails in a big way and loses coolant so fast that it fills one or more cylinders with fluid. If you are lucky it fogs the neighborhood but can pump it out until you shut down. Then the residual pressure fills one or two cylinders and if you try to start again you get a fluid-lock situation but do no additional harm. If you are less lucky it fills a little faster and locks up while idling, perhaps "lifting" a head. If you are unlucky it does that under load, doing all that and also bending a rod or two and maybe the crank.
But, from what I have seen and talking to guys who have dealt with many of these, real head gasket issues are less common than their replacement rate suggest.
Moral of the story: Run the correct coolant, monitor your temps and especially the delta, and deal with problems quickly. Not knee-jerk & replace everything at the first sign of something unusual, but pay attention and don't let problems fester because on these trucks more than anything I've owned, it gets expensive fast.
Last edited by sjsche; 07-27-2014 at 06:06 PM.