|Thermostat housing and water outlet on a 1998 Ford Crown Victoria police interceptor- other years similar|
Last weekend, I set out to replace the thermostat in a Crown Victoria as part of a routine cooling system service. This should have taken me about five minutes, tops: I've owned more than five Crown Vics in the past few years and have done fairly extensive work on Panther-platform cars. Plus, they aren't exactly mechanically complex machines.
At first, everything went smoothly: I unbolted the water outlet from the intake manifold, replaced the thermostat and gasket, and bolted the outlet back onto the manifold at the Ford spec of 18 ft-lbs. Fired up the car, bled the system, and.... a leak! Coolant was pouring pretty steadily out from the thermostat housing on the intake manifold. Puzzled, I checked the following, which would be the usual suspects for such a leak:
- The O-ring inside the housing was properly positioned on top of the thermostat.
- The hose connected to the water outlet was not leaking coolant. This is something to check, because if the hose wears out, it can leak coolant and it will run down the water outlet, simulating a leak from the thermostat housing.
- The thermostat housing was in great shape, with no pitting, cracks, or defects of any kind. I checked this thoroughly, because the Ford manifolds are well known to crack in various locations.
- The bolts were indeed torqued down to the proper amount, and they were torqued in equal increments.