I have two USA 2nd generation Diamantes (3.5L engine) and both began leaking engine oil from the camshaft thrust case on the front, driver side, of the engine. This is the little 2" diameter cap with two bolts holding it in place. It is on the end of the camshaft opposite of the end with the timing belt pulley. And, yes, I am sure this is were the leak is and not from the rocker arm cover gasket. Though the leak is minor, only 2 ounces per oil change, it makes a mess and also drips onto the starter motor, causing a recent failure.

To replace the O-ring of the camshaft thrust case, it requires removing the bolts. But the thermostat housing piping is in the way, blocking access. Removal of the thermostat housing is a difficult job. I am wondering if anybody has successfully backed out the bolts of the camshaft thrust case enough to apply silicone sealant around the perimeter, then re-tightened the bolts. And, if so, did that slow or stop the leak? I don't want to try this if just pulling out the thrust case out a bit would disturb the O-ring seal enough to make the leak worse.