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?

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-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

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

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

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!

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

^ 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...

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

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

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

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.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)