I've had a coolant leak for several months now and since I was going on vacation for a week I decided to drop my 2006 750I with 116,000 miles off to my Indy shop. My Indy mechanic is my 28 year old son who has been taking apart cars since he was a kid. A real prodigy.
The first step was to pull the exhaust and drop the tranny to get to the coolant cover by the block. He had access to see if it was leaking but it wasn't but we decided to replaced it anyways since he was there and I had the part.
The second fix was to put the tranny on the stand and to inspect the GUIBO joint. It was shot. He couldn't believe that I could still drive the car. This wear and tear caused a load bang when downshifting, especially between 2nd and first gears.
The third fix was to take the intake apart and get to the valley pan gasket. Sure enough, that was where my coolant leak was. Here is the fix that he did without having to buy the $450.00 tube kit.
He bought a new tube since the dealer doesn't sell the o-ring separate, He took the o-ring off the front part of the tube. He cut under the adhesive to remove the o-ring from the tube since it was glued on. He then inserted the pipe from the rear of the valley pan, instead of the front. He used a windshield adhesive to glue the o-ring back to the front part of the tube and let the adhesive set over night. He also used the same adhesive to put the valley pan cover back on. Next day, put the intake back on, exhaust, and tranny back in the car and finally I have the ultimate driving machine with no smell of coolant or no more fast jerking downshifting.