2000 Ford Expedition; 142,500, 5.4 engine!! i had question on air shocks in the back, the compressor kicks on and truck lifts but later on the shocks i guess leak air, and drops, so the compressor kicks on about every few minutes, but sometimes the truck stays lifted, Do you think the problem has to do with a bad sensor or if the shocks have a leak can that be fixed or has to be replaced completely?