I have a '98 Mercury Sable w/ V6 overhead cam.
Back in December 2003 I had the radiator replaced because it was leaking.
Everything has been grand. No problems whatsoever.
Last month, the temperature suddenly climbed very quickly. It was the
water pump. A couple of the fins on the pump had been knocked off, I guess
from age. The car has about 150,000 miles on it, and that was probably the
original water pump.
Had it replaced. It's been, oh, a couple of weeks or so and the car's been
running great and at a normal temperature.
Then today, I left the house and I drove along. Car was running at a
normal temperature for about 22 miles of highway speeds at anywhere from 60
to 70 miles per hour, depending on traffic. But about 22 miles into that
trip, the temperature started creeping upwards. It was climbing slowly
enough that I was able to get to a decent stopping point with the
temperature at about 70% of its maximum.
I let it cool off for a while. I removed the thermstat, thinking it might
have stuck, so I could get the car back to the house. I would basically be
backtracking my earlier trip.
This time, I drove slower, about 55 miles per hour until I made it about 17
miles into the trip, then seeing it was doing okay, I moved it up to about
63. Still doing fine. I reached a stop light, did my duty, then took off
again at a normal clip. The temperature started climbing. By the time I
was half a mile from the house, it was time to shut the car down at about
90% of its maximum temperature.
I let it cool down for about 20 minutes. The temperature gauge returned to
normal and I drove it on home and parked it without an increase in
Based on behavior like this, and keeping in mind the key points that the
radiator was replaced in December 2003, the water pump was replaced in June
of 2004, and I had removed the thermostat, what's your best guess as to
what's wrong here?