Monday, March 17, 2014

Ford 6.0L Oil Cooler Replacement/Repair

As Betsy reported, I spent all day Saturday getting our truck repaired. We knew we were starting our trip with cooling problems. The Ford 6.0L diesel has a long history of cooling system problems, some resulting in very expensive repairs (think $10K to $15K at the upper end). Through a Ford users forum, FTE - Ford Truck Enthusiasts, I have learned a lot about this truck and engine.  When it was apparent our problem was escalating, I was able to find a mechanic in the area we were staying. He is a Ford Master Tech and, as many do, he does side jobs at home. He has a roll around tool chest about the size of a small pick up truck. I had been in contact with him and set up a day to get the work done. He agreed to let me hang around and watch the process and we got along very well, sharing war stories with his educating me on the ins and outs of the 6.0L diesel. The problem is the oil cooler starts to plug due to a gel like substance that forms due to the antifreeze aging and temperature. The coolant goes from the oil cooler to the EGR cooler. The EGR cooler has very hot exhaust gases (800*F to upwards of 1500*F). The reduced coolant flow can't cool the exhaust gases and the heat turns the coolant to steam which, in turn, ruptures the EGR cooler allowing coolant to enter the intake manifold that can cause major damage to the engine. Fortunately I learned to monitor the engines vital statistics with aftermarket gauges (the ones on the dash are just fancy idiot light type gauges and often don't register a problem until after the fact). A new oil cooler and aftermarket EGR cooler, along with a few extras the mechanic did, and we are back in business. I'm looking forward to towing the 5er again to see what reading I get then. To initially test for a plugged oil cooler you have to be able to monitor your ECT (engine coolant temp) and EOT (engine oil temp). First you have to be fully up to operating temperatures and then drive for about 20 to 30 minutes at freeway speed on relatively level ground (not always easy). The difference (called the delta) between your ECT and EOT shouldn't exceed 15*F. Also, it is important that your thermostat is working properly. You should be seeing at least 188*F to 192*F ECT. This is the only way to determine your delta. Any other driving conditions have no relevance. Our delta was only 12*F but when towing a heavy load (our 5er is right at 14K lbs) we were seeing ECTs up to 230*F and EOTs 240*F and peaking on mountain passes at 258*F. That is the upper limit. Not good for the engine. At 300*F EOT there are some plastic parts in the oil filter housing that can literally melt. I've rambled on long enough. Time for some R&R.

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