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Old 03-15-2017, 12:15 PM   #1
dclovesdc
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diagnosing transmission oil cooler

According to bmw dealer, my 5hp19 is slipping at 3rd gear and requires replacement. What I noticed is that the transmission runs fine until it gets hot and goes into limp mode eventually. I touched the bottom of the transmission oil pan and it is super hot. I also touched the oil inlet & outlet at the oil cooler and I noticed that they both seem equally hot. I was expecting one side to be hot & the other side to be somewhat cooler. I am wondering if the transmission is running hot due to slip or slip is being caused by not cooling properly.

I noticed some posts in regards to coolant inlet being plugged at the oil cooler. So, I took the cooler out, along with thermostat at the bottom of the expansion tank. I ran water through the oil cooler using garden hose once it has been taken out, and I see good flow. Once I put everything back together with a new thermostat, oil lines still seem to be running hot. So, I am ruling out coolant side issue with oil cooler for the moment.

Next step is to see if I have issues on the oil side. I am going to unplug the outlet side, run the engine for couple of seconds, unplug the inlet side, and run the engine for couple of seconds. How much of oil should I expect to see flowing out? What would indicate if the cooler is working properly or not?

In general, I am also wondering how oil cooler fails, given no moving parts inside.

thanks.
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Old 03-15-2017, 01:12 PM   #2
jfoj
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Sometimes can be a problem with Stop Leak or the automatic transmission thermostat.

http://forum.e46fanatics.com/showthread.php?t=1123137
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Old 03-15-2017, 01:26 PM   #3
dclovesdc
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I don't have anything clogging on the coolant side of the oil cooler. I just replaced the thermostat when I took out the cooler out to examine.
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Old 03-15-2017, 01:28 PM   #4
dclovesdc
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I verified the coolant side of the cooler by running water using garden hose. going from coolant inlet to outlet, it gushes out.
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