Join Date: May 2011
Location: Minneapolis, MN
Drives: 1999 Merc Sable GS
3.0L OHV Vulcan V6 engine
Rep Power: 10
Unusual Coolant Leak
Hello. So here's the back story--
I was sitting in my car before work last week (just catching a few more comments from the local sports radio station) when I noticed that I had steam/smoke coming from under the hood. It wasn't a whole lot but it persisted so I popped the hood and discovered that I had a coolant leak. A quick look revealed that coolant was leaking out from the gasket where the thermostat housing meets the intake manifold. After I got home from work that day I checked on how tight the bolts were and they were pretty snug. I snugged them up a bit more just to slow the leak until I could completely replace the gasket. Everything seemed to be working just fine until I was sitting at the airport waiting for a friend to arrive. While I was waiting, with my car parked and running, coolant suddenly began spewing out of the expansion tank cap!! It was not slow leak either. I lost almost a gallon of coolant in less than 1 minute. I let the car cool for a couple minutes, refilled the expansion tank, capped it, and thankfully got it back home. A quick check at home revealed that the leak at the thermostat housing had worsened after the airport incident. The next day I changed the thermostat gasket and the expansion tank cap. Everything was fine until...
...about 15 minutes ago. I've been periodically checking my work and tonight I saw that coolant has started to slowly leak from the same spot. I just changed the gasket last Saturday. I can change it again, but that does not seem to be the root cause. I know that the housing bolts are tight. Could it be that my thermostat is failing the stay open after it has opened? (maybe that could explain the fountain of coolant at the airport--a sudden pressure build up from the thermostat closing)
Anyway, does anyone have any suggestions? Has anyone experienced this before? A flush is due, perhaps I have a blockage elsewhere? Failing water pump?