Collapsed upper radiator hose for '95 e300
 

After a long drive back from Chicago to Cleveland, I noticed the next day that my upper radiator hose was collapsed on my '95 e300. It stayed collapsed even after I loosened the radiator cap and drove it a short 2 mile local trip.

Temp on both trips came up to just over 80c on gauge and was steady.

I've changed the radiator cap in last six years since I've owned the vehicle with OEM cap.

Time to change the radiator hose? Thermostat issue?

It's either the cap or the overflow return line is clogged.

Should this upper radiator hose have a wire spring inside to prevent the hose from collapsing?

I had a bad cap when this happened to me!

^ This.

When the cooling system returns to ambient temperature, there needs to be a way for expelled coolant (which expanded when it heated up during operation) to flow back into the system, otherwise a vacuum will be created. A properly-functioning cap and free-flowing return line prevents vacuum from occurring. The collapsed hose isn't the problem, it's just a symptom.

Since the hose stays collapsed with the cap loosened (relieving vacuum on the system), the hose is softened to the point it's time for replacement, or there's a clog somewhere in the system that's preventing the vacuum from breaking in the main coolant circuit when you open the cap. Radiator hoses are cheap compared to the cost of engine R&R...

True, might as well replace the hose for good measure and cheap insurance.

I had that on my old E300 forever, but the vacuum broke immediately when I loosened the cap on the tank.

I later on put a metal coil in both upper and lower hoses - the same type you see in older american vehicles.