Hmm. Try walking over toward the lower-right hand side of the pit, over where Julian's racer should be. Look for a radio-like squawk-box like thing.
What should happen is that voice chat-box things should come out of the horns. If not, try clicking on the horns/box to see if that works. There might be a little bit of lag here, so give it a few seconds for the chat things to start appearing.
Otherwise, a glitch you have.