Thanks to all who have = responded. At Ken's suggestion, today I removed the expansion tank cap to have a = look and attempt a pressure test. Before I got to a test, out of = curiousity, I sniffed it for exhaust smell. Three guesses what I smelled and the first two don't count. I do wonder though, = when the engine is running, if cylinder pressure is pushing exhaust into the = coolant through some failure, wouldn't one expect that cooling system = pressure would then force coolant into the cylinder when the engine is stopped = and cooling? If this was happening wouldn't the engine miss or = stumble some on the next startup? Ours doesn't, it starts and idles = cleanly. Oh well. Looks like my fate is kinda sealed. Now, any ideas = how I tell which head is leaking into the coolant? As I said in my = first post on this thread, the engine was a purchased rebuild (Fast German Auto) = about 20k ago. Shouldn't be a need to pull both heads if only one = has a problem. I know that the list has beat the head gasket = issue 'til it's screaming for mercy, but I still don't understand why the wbx has = so many head related problems. Would a failure like this be corrosion? I've been using the orange stuff...