Your air cylinders are shot or almost shot. Just had mine replaced. Also replaced the air pump and dryer. Rides like a champ now. It’s very important to also replace the dryer adjacent to the air pump or moisture will ruin the new pump. That’s the voice of experience. Anyway, replaced the air shocks, dryer and air pump. Rides like a dream now.My 2005 Town car rear suspension sinks as I drive down the road, I stop and get out and check it out and it raises as I watch it. I drive down the road and it sinks again. I'm looking for tips on how I can start narrowing down what the culprit is.