Reply to "Leaking rear main seal - sometimes!"

Christian, like most things DeTomaso, repairing the seal is not a straightforward fix. This is because early 351-Cs used a 'rope-seal' in the rear main, retained by a small spike that prevented it from spinning. Later engines used a two-piece neoprene seal without the spike. From the serial #, your car may have either type seal if its never been overhauled. The rope seal is no longer available and in any case was tricky to install correctly so it didn't leak when new.

The later seal retrofits into early blocks by removing the oil pan, then the rear main cap and seal. With a small hammer & dowel, drive the little spike clear thru the main cap so it falls out the back of its through-hole. Seal the remaining hole in the main cap with a spot of RTV. Now the later two-piece main seal will fit the early cap perfectly. My spare engine (1970) had one of these and when I rebuilt it in 1992, I switched seals. Still running with no leaks!

I hope your car has been updated to late factory specs with a removable under-engine crossmember and e-brake bracket. If not, the engine & ZF must come out to drop the oil pan, as the early factory-welded crossmember will prevent pan removal. Good luck-