| | Leaking oil cooler 6.6 liter 2006 duramax
I just replaced the oil cooler in my 2006 6.6 liter duramax in an express 3500 van with 325.000 miles. The coolant tank was getting contaminated with oil. Head gaskets were replaced a year ago, when they were bad the radiator was getting over-pressurized and the engine would not turn over due to coolant in the cylinders. Did a complete head job with all GM recommended parts and sealants, also had the heads resurfaced, also replaced all head bolts. Now 1 year later noticed oil was accumulating in coolant tank, engine oil was clean with no water, engine was running fine. Did a coolant pressure test 20 psi.with the oil filter removed and could not detect pressure leaking from oil filter area. I decided to replace the oil cooler assembly anyways,cost from dealer was $318 plus the gaskets for the coolant to block passageways. Job was not too difficult and this was on an express van. I did an autopsy on the old cooler and I found one of the cooler to housing oil gaskets had deteriorated allowing high pressure oil to leak into the coolant waterway surrounding the oil heat exchanger. The oil heat exchanger itself was not leaking This is a brazed plate heat exchanger very heavy gauge metal and it would seem to take alot to cause a leak in this. Based on the diagram I got from GM I would suggest an easier and cheaper fix to try first before replacing the entire cooler would be to take the top off the cooler lift out the heat exchanger, check it for leaks and if its ok clean the mating surfaces,then replace these 2 heat exchanger to cover gaskets and the cover gasket and re assemble the cooler, I believe this could even be done without removing the entire cooler assembly from the engine, this would be a pretty straight-forward simple job. The dealer I got my parts from shows all the OEM gaskets necessary are available for this job. In my diagram they would be oil heat exchanger gaskets #573-#574- the oil cooler cover gasket is #576, and if the entire oil cooler assembly has been removed the oil cooler to block oil passage o rings are #254 and #99 are needed as well as #126 and #180 gaskets for the water return to rear engine block fitting are needed. If the coolant supply pipe from the front of the engine to the oil cooler is removed an o ring #99 and an oval gasket #95 are needed.I hope this helps.