I own a Saturn SC2 with a DOHC 1.8 motor. When I bought it in December 2004 it ran perfect. No issues what so ever. As soon as summer rolled around and the weather warmed up, the engine began to get a bit hot. I especially noticed it when I was driving down the freeway at speeds above 75mph. Our speed limits here in CO are 75 but most folks go about 80-85. Once I slowed down to 65 and turned the heater on it cooled down to normal temp. That was in early June. Later on in June I drove again on the freeway. It basically did the same thing only this time I was watching for it to see if it would do it again. On Sunday I drove to an area around here that is about 12000 feet. We live at 5000ft. On the way up it got hot but didn't over heat. Now by getting hot I mean it got above the third white line on the gauge but not quite to the red line. On the way back home I had the AC on and was running in second/third gear down the mountain and the the temp. didn't get above the first mark on the gauge.


#1: Do I have a blown head gasket/cracked head?


#2: Is my radiator bad?


#3: Is my thermostat stuck closed so as not to let the cooled fluid through to the motor?


#4: Whats wrong with my car?


I would really appreciate any input you folks have. Thanks

The behavior you describe sounds like the engine coolant temperature
sensor (CTS) needs to be replaced (at a minimum). Get the
new-style brass replacement from Saturn and also replace the wiring
harness as corrosion here will lead to bogus temp readings going to the
car's computer. You did not state the year or mi of your vehicle
-- if it is after 97, you probably have the new-style sensor -- but it
may still be bad.



Most DOHC S-cars will run just below 2nd tick (midpoint) of temp gauge
under reasonable driving conditions. When under heavy load,
sitting in traffic, and/or when the outside temp is higher, it is
entirely normal for the temp gauge to go up to near the 3rd tick - at
which point the auxilliary (electrically controlled) fan kicks in
--based on the CTS reading). This should bring the temp back down
to the midpoint on the gauge.



Since you drove back home with the AC on and the temp was not high,
this indicates to me that your cooling fan motor and relay are
functional, since the fan is engaged whenever the A/C is on (this is by
design). However, below the first tick is too low -- replace the
engine CTS.



(It is also possible that the temp sensor gauge that feeds the meter on
the dash is bad -- you may want to replace this one (note this is NOT
the same as the sensor that feeds the car's computer))



So, to answer your other specific questions:



1) head/head gasket -- no -- blown head gasket/cracked head
have many more nasty consequences and symptoms than you've indicated.



2) Radiator bad -- no -- you would most likely be losing
coolant and would probably overheat based on the pressure leak in the
cooling system if this were the case



3) Thermostat stuck closed -- no -- if it was, you would probably overheat adter the car ran for only several minutes --



4) See above



Hope this helps (for starters).

Please post resolution to the forum.



Derf

my sc2 did the same thing have someone check your cooliant cap mines was leeting air in so the pressure wasnt enough to push the cooliant

Thanks for the replies guys. Everything's been fixed. I took it to an auto shop that specializes in coolong systems. They diagnosed it and found that the previous owner(s) had mixed longlife anti-freeze with the regular stuff and that that combination had produces bad results such as mud like sludge in my radiator and my engine block. They did a manual and chemical flush to get it all out. They also replaced my cooling fan temp sensor because it was not engaging the fans at the right tempature. Due to the fact that my car may have gotten too hot they also replaced my thermostat. My radiator cap was bad so that was replaced as well. They told me that the fans on these cars usually turn on at 220 degree's and that its normal for them to run at 1/2-3/4 on the gauge. That seems to be a bit though. Is that normal? I admit though that the tempatue here in CO in the summer does range fromhigh 80's to low 100's everyday. Like last week we had highs of 107. I guess these temps do have something to do with the car running kinda high temps as well. Because in the winter our temps range 40 down to -18 or -20. And my car ran alot cooler during the winter than it has during this summer.