Turbo sound and wheel explosion dont want to sound anymore

Hi, the first time i played the 0.5 version i was amazed with the turbo and wheel explosion sounds, but today i dont have these anymore. I cleaned the cache, reinstaled the game, but they dont want to sound. I can heard the turbo whistle, but not the turbo backfire (i dont know if it's called like this). Any ideas? I really want them back

 

Sounds very similar to the problem I have located here http://www.beamng.com/threads/no-turbo-whistle-only-bov-sound.18291/#post-284766

Seems like no one knows how to fix it..