Engine having trouble keeping steady coolant temp

Possibly. Could also be signs of a defective cooling fan, defective AC fan, a clogged radiator, a bad water pump, or a leaking/blown head gasket too. What preventive maintenance has been done on the cooling system in this vehicle over the years? If it has been more than two years since the last complete radiator flush and fill, I'd start there with a good radiator flush.

Bob

I had a complete radiator flush at 80K, which was probably just under a couple of years ago.

One other thought: about a week ago, I got a low coolant light...I immediately pulled over and filled up with 100% antifreeze (about a quart) as I didn't have water to mix in with it. I've put about 250 miles on the car after that with no problems before this problem showed up. Could that be related?

when the coolant was changed did you change the thermostat also??

No. Just did a radiator flush and coolant change.

Assuming your fans are running correctly and there is no debris blocking the front of the radiator, I'd suggest you flush again now since it is nearly 2 years and due for this anyway. If possible, I also suggest use of a good radiator flush and follow all bottle directions. Make sure you get as much antifreeze out as possible before using it and then make sure you drain it a few times using fresh rinse water afterward, then fill to 50/50 minimum and

65/35 maximum (depends on where you live and coolest temp seen during winter). I also recommend the garden hose flush systems available from Prestone, etc. They do a nice job and you will see a lot of rust come out when you reverse flush the system. Also change the thermostat and make sure you remove and completely clean the overflow reservoir. I use my [pressure washer to get all that gunk off the plastic container. When refilling, use the Saturn approved correct fluid available from the dealer since Saturn is funny about what they recommend and most off the shelf coolants contain phosphates which is a no no for Saturn. Also, make sure you get the pellets from the dealer and crush and put them into the radiator as well since this will help prevent a head gasket problem.

If this still doesn't correct the problem, I'd replace the Coolant Temperature Sender next.

Good luck and post what you do and if it helps for others benefit.

Bob

Check to see that the plastic air dam is still under the car and hasn't been torn off. It has a measurable effect on cooling.

Lane [ lane (at) evilplastic.com ]

I lost both the air dam and the splash panel in a flood a couple of years ago. There's been no effect on cooling as far as I can see. Of course, I'm in San Antonio...

Maybe the cooling fan has packed it in. I recently lost the fan on my 91 SL2 and had cooling problems at lights and in slow traffic.

I can hear my cooling fan kick in when I pull up to my garage at night, just before I shut the engine off. I initially thought it was the cooling fan, but that wouldn't explain why the car actually runs cool at times.

The fan motor could have a bad winding. If so, it will not run reliably. The fan motor is cheap and easy to replace.

That still doesn't explain why the car actually runs cool at times, though.

I found that when I was moving in traffic, my car stayed cool. If I stopped at a light and the fan motor was not getting good RPM's, the enginre would get hot and the A/C would not cool well.

It turned out that the internals of the power connector on my fan motor was messed up. If I wiggled it, the fan would get full speed. So I would hit a bump and the connector got good contact it worked good... next bump, poor connections, poor cooling....

Anyway, 1 hour later (including the trip to the part store) and $25, the problem was solved.

Turns out the problem was a bad coolant temp sender. Replaced both (apparently, Saturns have 2), and the car's running fine again.