John Harmon wrote:
Scott Dorsey actually said:

Thirdly, if he didn't know any of these things, it should have taken him
less than five minutes to find the leak with a can of starting fluid. There
is ABSOLUTELY NO EXCUSE for someone to bring out the smoke machine for that
sort of leak unless they are trying really hard to find ways to bill their
customers for something.

This is dead wrong.
Everyone knows that hack.
It doesn't work for the E39.
It might have worked for 1970's era cars, but not the E39.
There just isn't any change in the engine speed no matter where or how or
what you spray on the underside of the plenum.
The leak is just too slight and the difference in engine speed too slight
and the chance of getting the fuel from the plenum to the plugs too slight.

If you're just spraying and not poking and prodding that's likely true, and
a lot of less severe hose cracks won't get found that way unless you are
pulling and stretching on the hose as you're hitting it.

But the plenum is easy, you just squeeze the body and shake it back and
forth. Of course, likely you won't even need the spray because it'll
come apart in your hands.

You are definitely right that the E39 is a lot more of a pain to find leaks
in than the E30 and earlier vintage cars and more sensitive to smaller leaks.
Sometimes the smoke machine IS needed. But sometimes you should be able to
look at the plenum and see cracks and just replace the damn thing whether or
not it's leaking, because you know it's going to start leaking soon.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."