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4thgenceli
09-08-2011, 02:30 AM
Symptoms, troubleshooting, etc.

Wife picked me up from the bus stop today. I glance at her gauges and see her temp gauges is PEGGGED red. Car seems to be driving alright, it wasn't that way when she drove the kid to school in the morning and it just happened sometime in the 2 mile drive to get me.

Coolant is spilling out of the overflow. Call a tow truck to come fetch the car and drag it home.

Waiting for the truck, I start the car. Temp is still well over where it normally sits, but the fans are not running (possibly relay failure or fan failure). Both radiator hoses are BLISTERING hot. Can barely touch either hose (thermostat failure?). Get it home, temps have returned to normal. Start the car, turn on the AC. Both fans fire up and are spinning (relay is not the problem).

So it is either a failed thermostat or bad temp sending unit. Oil is golden, no milky color its a nice brown (about time for a change anyway). Car sounds normal, drives the same as before, no loss in performance. Now to fix it tomorrow before she has to goto work. :sigh:

4thgenceli
09-08-2011, 02:36 AM
And now some more reading on the functions of the CTS on this car is accounting for some of the driveablity issues we have been experiencing for a while as well (rough idle, cranks longer before starting when warm, etc).

Hookecho
09-08-2011, 02:43 AM
Well, if coolant was boiling over you can rule out the sending unit.

lamont
09-08-2011, 02:13 PM
I would try unplugging the fan temp sensor in the radiator to see if the fans kick on while the car is still cool, if the sensor is bad it won't turn the fans on when the appropriate temp is reached, if when unplugged the fans don't turn on the fan relay is the problem. Also change the radiator cap if it is old, and check the thermostat by suspending it in boiling water to see if it opens when it reaches 170-190 degrees depending on the rating on the thermostat, don’t let it sit on the bottom of the pot it will be hotter than the boiling water. It could also be the head gasket as well. I just had to replace mine on my 94 GT and there was no oil mixing with the coolant and my oil was clear and not milky, but the head gasket was blown allowing exhaust gas to enter the coolant passages and pressurizing the coolant making it spill from the overflow. Test the cheap stuff first, but don't rule out the head gasket just because your fluids aren't mixing.

4thgenceli
09-08-2011, 03:23 PM
This car doesn't have a fan temp sensor on the radiator. It only has the 2 other sensors (one for the gauge one for the fan). I'll be replacing the t-stat and cap today and then hopefully it works. I really dont' want to do a HG on this thing, so hopefully it's not that.

UtahSleeper
09-08-2011, 05:51 PM
Does the coolant appear to be cycling when the rad cap is off? If there is no leaking, and no oil in coolant/coolant in oil then I don't know if I would jump to that.

4thgenceli
09-08-2011, 08:04 PM
So the thermostat is fine. Rad cap replaced, thermostat replaced.

Filled coolant, let it run for 20 minutes idling while I topped off the coolant and the cooling fan never turned on. Pulled out the connection and the fan turned on 10 seconds later. I need to test the coolant sensor now before I trust it to drive down to a shop.

4thgenceli
09-08-2011, 11:50 PM
Bruce..you suck.

It was what I thought it was (coolant temp sensor for the fan). After replacing the tstat and radiator cap I took it into PepBoys for a cooling system check. Block check passed (no exhaust or oil mixing) and no coolant burning out via the exhaust.

Pressure check, the new cap passed (duh). It was loosing pressure though slowly. Turns out there is a small crack in the radiator by the driver's side end cap at the top. Nothing major, but it accounts for the coolant that we replace every oil change. CEL was on for an EGR, catalyst and CTS fault. So we have a vacuum leak & temp sensor to fix.

Peace of mind FTW.