I have installed loss-of-coolant sensors in all my cars to catch early any leaks or cooling system failures. I've seldom had to use them until yesterday when sure enough, the lamp illuminated in one of my 940s. Reservoir had emptied and I watched a slow drip onto the driveway. After rooting around, I found that a heater hose had chaffed against the EGR valve outlet and was close to a catastrophic failure. Vibration had worn a deep ridge into the hose. I ordered a new OEM heater hose, decided to add all new hoses, water valve and a radiator to the order since everything was around nine years old, and will rebuild my cooling system. One more thing I do not have to worry about.
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