Overheating issue...

[barber107]

Just recently my car started overheating. It is an 87 LX-i hatchy with 140,000 miles on the ticker. I love this little car and I am afraid letting it get hot is going to hurt it.
When it is overheating the temperature will start to climb after it has been fully warmed up if I am not moving (i.e. waiting at a stoplight or intersection). Generally speaking, as soon as I start moving, it starts to cool back down unless I stop again. Sometimes it doesn't cool down unless I find a long enough stretch of road to get it some air.
At first, I thought it was the radiator fan because it wasn't coming on when the car was getting hot. I jumped the fan switch and the fan comes on and the car starts to cool fairly quickly. So then I was thinking it was the radiator fan switch, since the fan isn't on even though the car was on and over the normal operating temp, but I changed that switch and it is still overheating and I am not sure the fan is coming on. I tested the old switch (stuck it in boiling water and measured the resistance across the two leads) and it seems to be working, but I am not sure if that is the right test.
Does anybody have any advice?
What else could it be?
What other things should I be checking?
Thanks a lot guys!
~Barber

[MessyHonda]

did you make sure it has coolent at 50/50? when i got my car it would do the same thing....it had a cracked radiator and i changed it. like 2 weeks later the water pump gave up. i changed that too with all the belts since i was in that area working. now it works like a champ

[Vinny]

Have the system pressure tested, inclusing the cap to ensure that its not losing pressure. Also might want to think about changing the thermostat. Check the hoses to make sure they arent easily collapsed when the cars warmed up

[frantik]

i had this problem and it ended up being the computer modules underneath the passenger seat had failed.

here's the technician's notes he made during the diagnostic.. maybe they will help

Checked fuses 9, 12, 14 under hood - ok
Checked both cooling fan relay operation - ok
Checked ground to both cooling fan motors- ok
Checked fuses 1 and 12 under dash - ok
Checked ground to both coolant temp switches - ok
Jumped coolant temp switch A and passenger side fan operated
Jumped coolant temp switch B, no fan operation
Checked power and ground to fan timer unit - ok
Was able to activate both fans via a/c system indicating diodes are functional
Suspect defective "fan timer unit" - Recommand replace and test further
After timer unit replaced, radiator fan switch also found defective - recommend replace and test further

after that it was working again


the fan timer switch was expensive though..230 just for the part.. hopefully it's not that. other people fix the problem just by rigging their fans to always be on when the engine is on

[barber107]

Thanks for the notes, I will go through these until I get stopped...

But first,

1.) Where are the coolant temp switches?

2.) Does anybody know what this means...Was able to activate both fans via a/c system indicating diodes are functional...

Do I just turn on the AC and the fans should come on? If so, that isn't happening...

Thanks again,

Barber

[azazel_18_2]

First things first, check your grounds. I changed my valve cover gasket and forgot to connect the ground to the valve cover and the temp gauge went nuts. The more I pushed the pedal in at a stop or moving the cooler it would show. I doubt very much it is a fan thing. The radiator fan in my 89 lxi rarely kicks on even on a hot summer day like today. Replace your radiator cap first off. It sounds crazy but it can make your car overheat.

[salgmz]

im pretty sure its ur thermostat its only like 10 buks u should get 1 just to make sure and dont forget the thermostat gasket!!!dont use the original 1

[Dncdesign]

When it is overheating the temperature will start to climb after it has been fully warmed up if I am not moving (i.e. waiting at a stoplight or intersection). Generally speaking, as soon as I start moving, it starts to cool back down unless I stop again.


I had this exact same problem and it was the coolant as MessyHonda88dx mentioned.

DNC

[oldschool3g]

mines been doing the same thing kinda. I just recently got my cooling system flushed with new coolant, new upper hose, lower hose, thermostat. And just a couple days ago i got my koyo radiator installed and ran perfect. When i was like a mile away from home the tempature guage slowly went all the way up to hot...so i drove it back to the shop with the needle on hot, but while driving it went back to normal again. They told me the car was running fine so they replaces the temperature guage sensor...ran fine for a while but its doing the same thing again. Does anyone have any advise?..it would help alot

[MessyHonda]

mines been doing the same thing kinda. I just recently got my cooling system flushed with new coolant, new upper hose, lower hose, thermostat. And just a couple days ago i got my koyo radiator installed and ran perfect. When i was like a mile away from home the tempature guage slowly went all the way up to hot...so i drove it back to the shop with the needle on hot, but while driving it went back to normal again. They told me the car was running fine so they replaces the temperature guage sensor...ran fine for a while but its doing the same thing again. Does anyone have any advise?..it would help alot

yeah mine does it...i did not flush the system but i had to change the radiator and i put some fresh coolent and then my water pump gave up and drained the radiator and opened the bleed valve by the dizzy....put a new water pump and put some fresh coolent always at 50/50 my temp guage goes up when i run the car hard....like 4k rpm shifting and then sudden stop since of trafic...my guage does not go all the way to hot but it goes to the middle.....maybe we got junk in the block that restricts the coolent flow....(idk) just a wild guess.....good luck bro

[oldschool3g]

yeah it really suck...i ust hope its nothing serious. im rebuilding the whole engine soon...so that should help..hopefully

[barber107]

Sorry for being stubborn, but I still think it has to do with neither of the radiator fans kicking on. I think this because when I short the wire that turns the big fan one on, it cools the car down fairly quickly. Does that make sense to anybody else?

I replaced the radiator fan switch and it didn't help because the fan still doesn't come on even if the car is overheating. Yet I can jump the connectors and it'll come on and cool down the car.

Is there anything else I can do to test the radiator fan system? What about the a/c should kick them on? If turning on the a/c should kick on either fan, I have a problem because mine don't come on.

I'll check the thermostat tonight, but I just don't think it is the culprit. Is putting it in a pot of hot water on the stove and watching it open an adequate test? What temp should it open at?

Thanks for the advice and help!

Barber

[frantik]

They told me the car was running fine so they replaces the temperature guage sensor...ran fine for a while but its doing the same thing again. Does anyone have any advise?

it could be the Fan Timer Unit.. it's one of the modules underneath the passenger seat. this same advice goes for barber

unfortunately i don't know what that means bout the fans and the a/c system. I recal being told by another mechnic to turn the heat on and the temp slider to heat to activate the fans but i dunno if that was true or not

[barber107]

Thanks to all who made suggestions....

The car is fixed and running well. The problem was the thermostat and after replacing it, the car is back to normal.

Sorry for not yielding to those that suggested it in the first place. Apparently, you know more about cars than I do.

Thanks again.

Barber

[frantik]

sweet glad it wasnt anything too major

[oldschool3g]

hey guys, i know this thread is old...but i just wanted to say that my temp. problem is fixed now..turns out the stupid shop that installed my koyo radiator installed the wrong temperature guage sensor...from what my uncle told me..is that there are two types of guage sensors depending on your the cars guage...when the fan turns on one of them reads it at normal temp(which is right in the center)..and the other reads it when it reaches the top..which was the one they had installed. So basically my car was running perfectly fine...the sensor was just making the guage lie to me...lol.

[MessyHonda]

hey guys, i know this thread is old...but i just wanted to say that my temp. problem is fixed now..turns out the stupid shop that installed my koyo radiator installed the wrong temperature guage sensor...from what my uncle told me..is that there are two types of guage sensors depending on your the cars guage...when the fan turns on one of them reads it at normal temp(which is right in the center)..and the other reads it when it reaches the top..which was the one they had installed. So basically my car was running perfectly fine...the sensor was just making the guage lie to me...lol.

thats why i installed my own radiator myself....plus i saved a bunch of money...lol

[oldschool3g]

yeah i wouldve done it myself...but i have no garage at the time...so that sucked...but atleast its fixed now