Truck currently has 250,000 miles. The oil cooler failed about 125k ago. The radiator, water pump, and oil cooler were replaced and EGR deleted. Ford Gold went back in and a coolant filter installed.

ECT and EOT sensors are +/- 1-2 degrees after overnight soak.

I switched to a 200 stat with EOT temp around 224 at 75 mph about a year ago. Then I started noticing my EOT was creeping until it recently hit 235. Last weekend I did Restore, and then Restore Plus. Removed the water pump and the plate at the top of the oil cooler. I used a pressure washer to backflush the oil cooler. With the water pump removed everything washed out instead of back down in the block. Replaced the water pump with a brand new OEM to rule out cavitation issues. Filled the cooling system with red CAT ELC and put in a 185 stat to replace the 200 stat I had been running. At 60mph, ECT is currently 188 and the EOT is 121 - or essentially the exact same temperature difference as before the flush when I had a 200 stat and 235 EOT's. Backflush and new waterpump did nothing for me.

I've read a tiny bit about an oil cooler bypass valve in the oil filter housing. Are these proving to be problematic instead of the oil cooler being clogged? How do I determine if I need to replace the oil cooler again, or something else? I would have thought the backflush would have at least given me a small improvement. NADA.

Thank you for the input!

 

You could have a problem with the oil cooler bypass, but I would suspect even though you flushed the oil cooler that it is still partially plugged, the passages are hard to flush due to design and size, also your thermostat at 185 degrees is too cold for a 6.0, an OEM is I believe 192 and the Mishi is 200. I run a Mishi in the winter and an OEM in the summer and see about a 7-8 degree spread year round, in the summer I can see 20 degree delta when towing about 18K. Also the test for delta's is at 65 MPH I believe so your numbers may be off.

 

Thanks for the advise I suppose I'll change the oil cooler and see where that leaves me. I'll leave a post with results.

 

Does anyone know the part number for the screws for the cap you remove to backflush the oil cooler, I dropped one and can not retrieve it and the Ford parts guy looks at me like I am outer space.