Also check out the hose itself. I have seen instances where the clamp was overtightened causing a tear in the inner layer of the hose (most hoses are multilayer separated by fiber mesh). With the inner layer torn, the strength of the hose is compromised and it can expand like a balloon under pressure. The heat and pressure may have softened the hose over the last 6 months.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280