Back in the early days of the automobile, Detroit was a bubbling cauldron of ideas and innovation. It was the automotive equivalent of what Silicon Valley is today, an exciting mixture of creative engineers and inventors blended with a healthy dose of demanding investors. Things got done!

And yet, Detroit’s early auto makers didn’t believe they had a lock on the best ideas. They constantly sought for better ways to make cars, no matter where those ideas came from.

The legendary head of research at General Motors, Boss Kettering, was known to travel the country, checkbook in hand, buying up patents from independent inventors, always trying to stay a step ahead of his competitors.

But it doesn’t work that way these days. In fact, throughout my career I’ve heard frustrating stories of how hard it is to bring outside ideas into the “Big Three.” I’ve even heard these complaints from giant multi-national supplier companies. They all tell the same story: Europeans and Asians are far more open to outside ideas than auto makers in Detroit.

To be fair, much of that technology typically was related to boosting fuel efficiency, which was hard to get U.S. car buyers to pay for when gasoline prices were dirt cheap. After all, if your customers don’t want to pay for a technology, why offer it?

Also, auto makers have to be careful about how they bring ideas inside. A company may be sued if someone shows an idea to an auto maker it already is developing on its own. As soon as the new design comes out, a cranky inventor can claim his idea was stolen.

Recently, we’ve seen Detroit actually get to market first with numerous types of infotainment systems. But this was accomplished by collaborating with huge electronics companies, not individuals.

Independent engineers and inventors tell me it’s still very difficult to breach the castle walls. The problem is that when they bring an idea to an auto maker, it typically gets evaluated by the person or people who are experts in that area of technology.

That makes sense. But if the new idea is a threat to an existing design in process, it almost always is rejected. No one wants an outsider to kill a pet project.

As one of my independent engineer friends tells me, “It’s gone beyond NIH (not invented here); it’s what I call NIBM, not invented by me.”

He suggests auto makers, especially those in Detroit, develop truly impartial evaluators to assess new ideas and create mentoring programs to help outsiders bring their ideas inside the castle walls.

Auto makers assure me they do a great job of finding new ideas, but I’ve heard from enough independent inventors and suppliers to know that only the car companies believe this.

There still are lots of creative types in the Detroit area: People who know how to design, engineer and make things. Auto makers need to do a better job of tapping into that knowledge, mentoring it and using it. Not only would it be good for the auto makers, it would ensure that a creative class of engineers, designers and inventors keeps renewing itself, generation after generation.

John McElroy is editorial director of Blue Sky Productions and producer of “Autoline” for WTVS-Channel 56, Detroit, and “Autoline Daily,” the online video newscast.