Was washing the car(2002 xj sport) this morning. I always pop the hood to wipe the engine down. Saw the hoses collapsed. I loosened the cap on the expansion tank, and the hoses returned to normal shape. What do I need to check to find the culprit?

How many hoses were collapsed, you only show 1. Feel them for pliability, ..when was the last time you replaced them? What had you been doing before that to heat up the system?

Pic 2 is also collapsed. It just doesn't show up on picture. I haven't driven the car, or started it today. Drove it yesterday evening. Normal drive. I've never changed hoses, otherwise cooling system is new.

The coolant cap is 'supposed' to allow the coolant from the atmospheric catchment tank to return to the reservoir when the coolant temp drops and creates the pressure differential.

There is something wrong with the cap, line or catchment tank.

bob

Thanks Bob. The catchment tank is the one by the left tire, correct? I'll start the diagnosing by replacing the cap. The reservoir and cap are new, but we'll see.

That's just vacuum -- betting on the cap

Collapsed hoses is generally caused by low coolant in the system. You need to burp or purge the trapped air from the system.