N63 Leaks Coolant

[Davidf]

Although my '08 E70 has an N62 engine, my '12 F10 has an N63 like yours. Unfortunately, both engines have a rear coolant cross over cover that is located within the transmission bell housing. So, the transmission has to come out to replace the cover.

But, before you settle on the cross over cover as the culprit, you should carefully inspect your coolant system vent lines that come off each head to a plastic "Y" fitting. It is simply a matter of time before the plastic "Y" fitting breaks and leaks coolant. Since it is a vent, it would not dump coolant but rather a liter or so every few days. The "Y" is located on the left front of the engine just on top of the valley pan. Most of us simply remove the plastic fitting and replace with a 3/8" brass "T" barbed fitting. Or, you can use nylon but not sure of the longevity of nylon.

You have to remove the turbo intake hose between the intercooler and turbo to really see the "Y" fitting. But, if you look below all the crap in the way just right, you can see it without removing anything. It is not related to the turbo coolant lines.

The coolant that leaks from the vent "Y" fitting pools on top of the valley pan and drains to the rear of the engine. The rear of the engine has a weep hole that exits within the transmission bell housing. The coolant finds it way down and drips from the bottom of the bell housing. Thus, you would think the rear cross over cover is the source...but usually not.

Hope this helps.