2001 LaSabre - Odd Temperature Issue

Well, I got a strange one here...

I've only had this car a few months, and up until the last couple of weeks, the temperature gauge never got above 211.

Well, one fine day when the outside temp was around 66 degrees, and with no AC on, I was stopped at a light, and all of a sudden I see the gauge starting ticking up fairly rapidly. When it got to 220, I turned the heater on full blast and it came back down to 200. I turned the heater off when I got going again, and it behaved at 196 until I got home.

Note: whenever the temp starts going up like this, the car seems to be idling rough. It's got new plugs and wires, and ran smooth at idle until this thing started happening a couple of weeks ago.

As an experiment, when I got home I just let it run in park. It took 6 minutes to go from 196 to 224, and when it got to 224 the engine seemed to smooth out again, and then it dropped down to 209. When it creaped right back up to 214, I shut it off.

It seems like the thermostat is taking too long to open up, but I'm not sure that would cause the rough idling.

I wonder if the water pump bearings are going bad. Would that cause some vibration to the steering wheel?

The coolant is topped off and the reservoir is full.

I hooked up an ODB II reader to it and there are no codes at all.

Thanks for any insight y'all can give.

Phil

This may not be a problem, my 2003 does the same thing, then at 224 the fans come on as they should and the temp drops, as the fans run there is a sensation of engine roughness as the fans are not really balanced and do set up some vibration. Look for the fans to go on using the dic to monitor the temp, or the scanner.

This may not be a problem, my 2003 does the same thing, then at 224 the fans come on as they should and the temp drops, as the fans run there is a sensation of engine roughness as the fans are not really balanced and do set up some vibration. Look for the fans to go on using the dic to monitor the temp, or the scanner.

I agree with Max. Mine turns the fans on at a fairly high temp and then the temp drops down to 203 or so and we start up again because the fans turned off. I turn on the air conditioning in low speed just to keep the fans on in traffic or sitting on warmer days. When the ambient if 40 degrees, the radiator cools without the fans.

I also found if I ran the motor at 1800-2000 it would slow the rise of the temperature by circulating through the radiator to lose heat indicating he thermostat is opening okay.