I always found that the pilots having a good working knowledge of the engines/airframe, really helped when faced with troubleshooting unusual snags. As long as they don't tell me how to fix 'em, I won't tell them how to fly .....
I'd just like to add that i've always had that little bit extra admiration for the drivers who took the extra time/effort to be involved in the tech/mech/elec side of the aircraft and/or troubleshooting. Yes, I know they don't have to and some will quite happily admit that the only part of the aircraft they see is that between door 1 left and the cockpit.
Once on an overseas operation with limited manpower/resources, we had one Capt who came out to the ramp on one of his days off with us mech's just to 'see' and help out with what we do to keep the operation going. It was most appreciated - after all he could've been sitting in the bar or in the pool at the hotel but chose to come out with us. Not only was it a great 'social' gesture on his part, he learnt quite a lot of what it takes to keep those babies serviceable.
For any pilots reading, if you ever get the chance, or 'make' the chance, don't be so quick to walk off and get straight on the crew bus, come down and have a look around with us mech's. I'm sure you'll find it a learning experience and very interesting. Come on, you must have wondered what is lurking under those engine cowls/ panels at some stage!
I know every time that i've been asked to visit the cockpit/simulator/crew briefing etc with you guys, i've jumped at the chance. I've learnt a whole lot about what your side of the job entails and this has helped me to see things from your point of view.
As for the original post about a pilot not passing a type engineers course - so what, although I can operate the aircraft and get it off the ground and (most times in my sim experience) get it back to mother earth, there's no way that I could pass one of their simulator/recency checks. Hell, i'd have a hard enough time passing the type 1 medical check!