peeing on the wheel

I had a dog whose name is Hoover; he is a german shepard. My dog is very friendly and intelligent but from last few days, he is showing obsolete behaviour.

He start peeing anywhere if he see another dog peeing. He does not pee on another dog's pee but where he is standing, there only. Also, now he is very interested to pee on cars.

He pee not on the tires but on the doors, both the bumpers, mudflap everywhere he can. Many times, he lift his leg to pee but nothing comes out. I had tried to teach him many times not to pee like this but nothing had happened.

I am in a very big problem; all my neighbours are saying bad things about Hoover and don't like this. He pee on my neighbour cars and rarely on his(my) car. If he pee on his car, I don't have problem.The problem is my neighbours and not Hoover. I don't want to give him punishment.

Kindly, help me and my Hoover.

[Fourpaws]

Why don't you not walk him near other people's cars? Of course, no off leash time unless your at the dog park or your back yard.

[have 2 kids]

Fourpaws is right.   Don't walk him close to cars - then he can't pee on them.  

[OscartheBully]

I think it's cute actually. Oscar use to do that, but we found out it was because FEMALE dogs lived in the house where the car was parked.
He was just trying to pick them up.. Human men pick up women oddly.. so I'm not gonna put it past my bulldog to do the same. ;)