Overheating Issue

[cmzinner]

CAR: 89 lxi
SYNOPSIS: The car keeps overheating because the radiator fans won't kick on.
WHAT I'VE TRIED: I've bypassed the thermo sensor - like the online manual says - and yes, the fans did run then I did what I though would fix the problem and I replaced the radiator's thermosensor, but the problem still remains. The car overheats after idling for 5 minutes or so. Fans never kick on.

Please help me. All advice is greatly appreciated.

[danronian]

Well I would BET you have a bigger problem than the fans. No car should overheat in five minutes at idle even with the fans. In the summer when it was 95F plus around here my fans barely ever came on and the temp gauge never goes above half. You probably have either a clogged radiator, are out of coolant, the thermostat is stuck shut, or you have a blown head gasket. Since you know it isn't the fans, try the thermostat next since it's the cheapest, also look to see if you have coolant in your oil and vice versa.

[shepherd79]

replace the thermostat. they are cheap. don't forget to get thermostat gasket.

[nswst8]

There is probably sediment on the bottom of the radiator interfering with the sensor a good flushing with the thermastat changing.
You should not be overheating just cause the fans don't come on.
Hope this helps. LOL
NSWST8 :cheers:

[cmzinner]

first off, thanks for the posts. YOU ROCK!

alright, I'll give the thermostat a change. perhaps I exaggerated a bit on the time it takes to overheat. it's more like, if I drive it and get it warm, then let it sit somewhere where no air goes through the radiator, it will overheat in 5min, with fans never coming on. By overheat I mean that the needle_climbs_to_and_almost_touches_red - turning on the heater will bring the temp down to midrange.

besides that, the radiator is only about 1&1/2 or 2 years old; always has adequate fluid and mixture (i'm a stickler about that); and it's only been about 8 months since I last I flushed her and replaced hoses. the radiator looked ~95% clean when I replaced the thermosensor, but when I do the thermostat, I'll douche it all again

[Chadroper]

Try taking the radiator out and flushing it out. Also check the tension on the water pump belt. Then there is also a bolt on the base of the exhaust side of the block take it out and flush out the coolant. I would also check the fan motors to see if they are good and also check the fuse or relay. You may also want to check and make sure your igniton timing is right.

[Blkblurr]

Your thermostat has fallen apart and is stuck in the closed positon. Happened to me. Your radiator fan won't cycle because the hot anti freeze is not getting to the radiator due to the closed thermostat. Good description of your symptom!!! wish all were like that
:cheers:

[cmzinner]

yeah, that's what I'm starting to believe...it seems to be the general consensus.

....but I'm going to have to wait till this weekend to work on the car again, b/c I have a dynamics test on friday to study for. :help: Anyone else out in 3geez land a mechanical engineer/engineering student?

[Blkblurr]

I drove mine home when it happened. Problem was I was 2 hours away and it was summer. I ran the heater at full to cool the engine a little.

[Blkblurr]

Good luck on your test. I am an Electronic Engineer with a mech minor but it' been a while since I did statics and dynamics

[cmzinner]

I drove mine home when it happened. Problem was I was 2 hours away and it was summer. I ran the heater at full to cool the engine a little.

wow..I just read your bio, and found out you're a mech.engineer...and btw, my overheating problem happened first when I was driving back to Orlando (school: UCF) from home in Jacksonville – also a 2 hour trip. I blasted the heater intermittently nearly all the way back to my apartment, whenever the flow of traffic slowed to a crawl (stupid road construction!!!)

[cmzinner]

Good luck on your test. I am an Electronic Engineer with a mech minor but it' been a while since I did statics and dynamics

hey, thanks.

[Blkblurr]

Always happy to help especially a fellow engineer / student
:cheers:

[Chadroper]

My thermostat failed once in a semi closed position. The car would start to overheat at speeds over 70mph. If the engine was running faster than 3000 rpm in 5th the needle would start to go up. If I slowed down so it was running about 2500 rpm or less the needle would go down.

[Blkblurr]

Good info for future reference.

[Mac]

Changing the thermostat, flushing radiator, and bleeding the system all should help. But after all that is done and if the fan still doesn't come on you might want to check the thermo sensor switch.

A while back mine was bad, and I got an aftermarket one from an auto store that didn't work. I then went to a different auto store and that one didn't work either. So I hooked a meter to each of them and dropped them in a pot of boiling water and neither one closed. Finally I went to a junkyard and pulled a few and tried them in the boiling water and they worked. One from the junkyard is now in my car and working just fine.

This was my experience. Not saying the one you bought is bad. Just passing on what happened to me.