Engine having trouble keeping steady coolant temp

I have a 1993 SC-2 with 105K on it. Up until now, the temperature gauge has
always been quite steady in all types of weather and driving conditions,
typically staying just below the mid-point, or just above it. I just noticed
that the engine runs hot when I have the AC on (it goes over 3/4 of the way,
but not quite to the red danger zone) and, without the AC, I've noticed a
more than usual fluctuation in the engine temp. Going up hills will send the
temp close to 3/4, and going down hills can send the temp to below 1/4. Even
during steady driving, the temperature needle seems to wander around much
more than I remember.

Is this a case of a broken thermostat, or perhaps a faulty coolant temp
sensor? If so, how hard are they to replace?

"MPost" > wrote in message
...
> I have a 1993 SC-2 with 105K on it. Up until now, ...

> Is this a case of a broken thermostat, or perhaps a faulty coolant temp
> sensor? If so, how hard are they to replace?

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?

"Bob Shuman" > wrote in message
...
>
> "MPost" > wrote in message
> ...
>> I have a 1993 SC-2 with 105K on it. Up until now, ...
>
>> Is this a case of a broken thermostat, or perhaps a faulty coolant temp
>> sensor? If so, how hard are they to replace?
>
> 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
>
>
>

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

No. Just did a radiator flush and coolant change.

> wrote in message
ups.com...
> when the coolant was changed did you change the thermostat also??
>

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

"MPost" > wrote in message
...
> No. Just did a radiator flush and coolant change.
>
> > wrote in message
> ups.com...
> > when the coolant was changed did you change the thermostat also??
> >
>
>

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 ]
---
Visit my Saturn Car Audio and Performance Page at http://www.evilplastic.com



"MPost" > wrote in message
...
> I have a 1993 SC-2 with 105K on it. Up until now, the temperature gauge
has
> always been quite steady in all types of weather and driving conditions,
> typically staying just below the mid-point, or just above it. I just
noticed
> that the engine runs hot when I have the AC on (it goes over 3/4 of the
way,
> but not quite to the red danger zone) and, without the AC, I've noticed a
> more than usual fluctuation in the engine temp. Going up hills will send
the
> temp close to 3/4, and going down hills can send the temp to below 1/4.
Even
> during steady driving, the temperature needle seems to wander around much
> more than I remember.
>
> Is this a case of a broken thermostat, or perhaps a faulty coolant temp
> sensor? If so, how hard are they to replace?
>
>

On Wed, 3 Aug 2005 22:41:01 -0500, in rec.autos.makers.saturn "Lane"
> wrote:

> 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.

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...

In article >,
William Hughes > wrote:

> On Wed, 3 Aug 2005 22:41:01 -0500, in rec.autos.makers.saturn "Lane"
> > wrote:
>
> > 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.
>
> 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.

"ORVAL FAIRAIRN" > wrote in message
news
> In article >,
> William Hughes > wrote:
>
>> On Wed, 3 Aug 2005 22:41:01 -0500, in rec.autos.makers.saturn "Lane"
>> > wrote:
>>
>> > 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.
>>
>> 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.