If you have an X-Drive AWD BMW, the front differential is mounted to the side of the oil pan, and the right front drive axle runs through a sealed pipe through the oil pan. There are two aluminum covers which retain oil in the oil pan. I originally made a repair to one of these covers 2 years ago when I removed the engine to replace the turbos and do the oil pan and head gaskets. This repair failed almost immediately, and this post will explain why my original repair failed, and what I've done to make sure it doesn't happen again.
 |
| Right side of the N54 oil pan, with the right side drive axle and bearing support removed. |
Following my initial repair, the plate started leaking immediately. The engine had been reinstalled in the car, and the bearing support and drive axle already replaced, and the suspension bolted up and torqued. I didn't have the time or appetite to tackle the leak then, so I waited almost 2 years until I had a few other projects to work on to tackle this again. To start with, I removed the right side drive axle (half shaft) and the bearing support. Then, I removed the cover and discovered how little sealant remained between the sealing surfaces. The sealant remaining was brittle and was removed quite easily. I followed the sealant manufacturer's directions (wait 1 hour before applying full torque) but this delay is much too short to avoid squeezing out most of the sealant. This was my critical error.
 |
| Previous repair squeezed almost all sealant out of the gap between the sealing surfaces |
Clean up the mating surfaces. I use a plastic bristle brush, a plastic scraper, and scotchbrite pads soaked in brake cleaner to get the surfaces perfectly clean.
 |
| Plate cleaned up, old sealant removed, ready for re-sealing |
I removed the bearing support and right drive axle without draining the differential fluid. I lost a very small amount of fluid through the axle tunnel, maybe 50ml or so (2 oz). I should top up the diff fluid when I complete the repair. Mating surfaces are clean.
 |
| Oil pan mating surface cleaned up, ready for resealing |
The last repair, I used a tube of sealant which I had on hand and was already opened. This time, I planned ahead, and made sure I had a fresh tube of new sealant for this repair.
 |
| Permatex Ultra Grey Gasket Maker |
Following manufacturers directions, I applied a 1/4" bead to one surface (the cover), and then assembled the cover with the fasteners, but not applying any torque. Just closing the gap to approximately 1mm, as evenly as possible on all sides.
 |
| Apply sealant to one sealing surface (not both) |
 |
| 1/4" 5mm bead of silicone, Circling the fastener holes (recommended in sealant instructions) |
I waited 48 hours before applying torque to these cover fasteners - 2 N-m only. This seemed to compress the silicone nicely. I'll fill the oil pan with oil and check for leaks before replacing the drive shaft and bearing carrier - just in case I still have a problem.
 |
| Maintain a 1mm gap between sealing surfaces, wait 48 hours before torquing fasteners |
The engine oil was refilled, and after another 48 hours, absolutely no sign of oil leaking from the plate. Looks like it will hold.
 |
| Mate surfaces, but do not torque the fasteners. Tighten just until some sealant comes out of the gap |
I've also found that I have a minor leak just above this repair - at the bed plate to block interface. A few drops of oil are seeping out around two of the bolt heads. To make this repair - the engine has to be removed from the car, and the bedplate removed (which provides access to the crank and crank bearings). This engine is at 205,000km now (approximately 130,000 miles) and this is a repair that I'd like to put off indefinitely. At least the oil pan to block gasket has held up nicely, no leaks so far. Same for the head gasket and valve cover gasket.
If you have any questions, don't hesitate to ask in the comments below.
No comments:
Post a Comment