Hi all, I need some advise because right now I'm in denial 
Late 2014 E class 2.2L Diesel CDI. 180ish Thou miles. About 4 months back the drip of oil under the oil cooler became a flood and I installed a new oil cooler. I kept a close eye on everything related for a couple of months and everything seemed sweet (both oil and water systems). One day a few weeks back (about 3000 miles after fitting the cooler) I was driving on a warm day and got a strong smell of both oil and coolant. Head under the bonnet the next day, the oil cooler is looking fine but the expansion tank is now black with oil.
This week I removed the new oil cooler assuming given the timing the new part may well have failed internally. It is as clean as the day it went in! I rigged up an internal pressure test last night. Maybe not an overly efficient home rig setup but I still have no cause to doubt the new part.
So all internet fingers are now pointing to a head Gasket issue. Is this really the case or is there something else to consider? Following are a list of observations that may be worth mentioning:
. I can find no trace of coolant in the oil, no smell, no mayo, oil filter is clean
. I pumped the expansion tank out, then used drain for radiator, what came out the radiator was clean.
. Water from oil cooler and EGR cooler was clean
. I could see no air bubbles in expansion tank with engine running
. Seemed to be no pressure issues with the cooling system.
. There was no white smoke from the exhaust
. The car was left to stand for 3 weeks after I found the issue (family vacation), no loss of fluids whilst gone and started first time cleanly
Thoughts / Questions?
Late 2014 E class 2.2L Diesel CDI. 180ish Thou miles. About 4 months back the drip of oil under the oil cooler became a flood and I installed a new oil cooler. I kept a close eye on everything related for a couple of months and everything seemed sweet (both oil and water systems). One day a few weeks back (about 3000 miles after fitting the cooler) I was driving on a warm day and got a strong smell of both oil and coolant. Head under the bonnet the next day, the oil cooler is looking fine but the expansion tank is now black with oil.
This week I removed the new oil cooler assuming given the timing the new part may well have failed internally. It is as clean as the day it went in! I rigged up an internal pressure test last night. Maybe not an overly efficient home rig setup but I still have no cause to doubt the new part.
So all internet fingers are now pointing to a head Gasket issue. Is this really the case or is there something else to consider? Following are a list of observations that may be worth mentioning:
. I can find no trace of coolant in the oil, no smell, no mayo, oil filter is clean
. I pumped the expansion tank out, then used drain for radiator, what came out the radiator was clean.
. Water from oil cooler and EGR cooler was clean
. I could see no air bubbles in expansion tank with engine running
. Seemed to be no pressure issues with the cooling system.
. There was no white smoke from the exhaust
. The car was left to stand for 3 weeks after I found the issue (family vacation), no loss of fluids whilst gone and started first time cleanly
Thoughts / Questions?
