Had same prob w/ 1999 4 cyl. Temp noticeably hotter then ususal and cooling fans won't spin. Relay's check, jump power directly to the battery - fans spin, next is the sensor but when replaced on the older brother, no change. New thermostat and double checked the water pump which was new 2 years ago - checked out just fine. No noticeable leaking except out the pressure exhaust out the resevoir when overheating occurs. Hose to water pump (can't remember if upper or lower) from radiator doesn't seem to be nearly as hot as the opposite hose which suggest poor circulation. Next is removing radiator for inspection (please nooo!). Can't find any tech. info. anywhere that says what triggers fans to spin (i.e. temp trigger and/or other variables) but when the coolant is boiling, seems the fans (at least one) should turn on. Thinking mulitple issues but hot running ruined my other GA. Running on one car for a 3 car family b/c I'm not lettting this hit the road until solved. Any ideas?

 

Have you tested at all for a blown headgasket? And you said you most definitely swapped the fan switch (sensor) correct?

 

Thanks much for looking at this. No to the headgasket. I did have an exhaust manifold repair about 2 years ago. There has been no noticeable performance deterioration - wouldn't a blown head gasket manifest itself that way? How do you check for a blown hg? I did not change the sensor yet, my reference was to the exact sequence of problems in my '99 GA where I did change the sensor with absolutely no change in the behavior of the fans and continued overheating of the coolant. Do you have any ideas on why the fan(s) won't spin even after a working sensor has been installed with a clearly overheating coolant system? Just read that sometimes the computer gets confused and a reboot (taking battery offline for about 8 hours) cured the problem for one guy (but his was a Sunfire - I'm desperate). Sorry for the many questions but the dots just aren't connecting. Again, much obliged for you time and intel.

 

You can do a combustion leak-test. You can get a testing kit for it, its a simple test really. It tests for exhaust gases in your coolant system and if there are those gases, the liquid in the kit will change colors to reflect that.

If the car has AC..and you turn said ac on, one of the fans should also come on.

There are actually 2 sensors on the pre 2002 models..
One for the gauge and one for the fan

Try getting the fans to come on by putting on the AC..
Then try replacing the Engine Coolant Temp sensor for the Fan

The sensor runs around 7-12 dollars at most auto parts stores.

Then if your still overheating, etc. I would perform the combustion leak test and go from there.

 

Thanks.. I'll get on this and let you know.

 

Got the kit, read the instructions; how do you test when the radiator has no neck, i.e. got an upper and a lower hose and a resevior feed but there is no top end openning to insert the tester nozzle into (which cannot "dip" into the coolant). Removed top plastic guard just to see if there was some top end opening (such as a typical radiator cap). If it's there, I'm not seeing it. Thought about coming in from the side where the resevior feeds. Seems like the only way but have to drain at least half the coolant as it enters the radiator a little above mid section. Is this where to insert the tester nozzle end?

 

Overheating is obviously common on this car from research I've done. Could be many things so starting with a thorough flush through the heater core and will remove radiator for inspecting and flush. Trouble getting heater core hoses off. Seems like the hoses are fused on to the stems and no room back behind engine to get leverage to pull them off. I guess they need to be wasted? Tugged all I can and they don't budge. Are there tricks to something like this/special tool(s)? Anyone else take this road only to find the car still overheating? Waste of time?

 

Can you turn the hoses a bit to break them free with a pair of pliers? I'm not even sure if there is room to do that..

 

I'm back...new hoses for the heater core (heater core seems to have no problems flushing, so I detect no problems there). Have new fans..they really were problematic as after installation, they began spinning just fine. That said, mechanic detected no combustion gases so presumably no internal leakages, but in less then a mile, the coolant has almost completely boiled out, internal temp gauge measure well over the 230 mark - I'm used to seeing it at slightly less then 200 before the problems began. If the fans are blowing, have a new thermostat, heater core not clogged, temp sensor working fine, relay's working fine, water pump checking out just fine (relatively new but disassembled and reassembled anyway), what in the blazes is causing the engine to overheat?