I'm new to this site, my 94 markviii's front air will only stay up when it chooses. The thing is I have found that when it does go down I hear a hissing noise, then it lowers. If I turn the car off and then on and it will rise and equal out in the rear and then the hissing starts and the front drops,Here's the tricky part, If I bounce on the front where it is hissing, the hissing stops and it equals out and I can drive it. Sometimes for days, others just hours.It always goes down in front after sitting for 12 or so hours, sometimes there is no problem, others I have to bounce on it. Got any ideas?? Maybe a valve or a sensor not making proper contact??