Cooling fan not turning on- I'm stumped!

[sunofogun]

Okay heres the background: 89 Accord LX
Dec. 05 I replaced cooling fan thermosenor in the radiator,thermostat, and radiator hoses.
Nov. 06 New water pump and belt and has been working fine since.

The other night I was idling my car for maybe 10 minutes when I realized the temp gauge was at the top and steam was coming from my hood.
I checked it out and somehow coolant was leaking from around the bottom of the rad or maybe the reservoir, but it was real hard to see with the car on the ground. The hoses were dry. Also I noticed the fan was not running. So I topped off the rad 30 minutes later and let it run again. Guess what ? no coolant coming out , but the hoses both stayed cold. So I got it towed to the shop I work at to make sure the head isnt leaking or anything really bad. So, she passed the combustion leak test but failed the rad cap. I replaced it. I used an infrared thermo and the coolant was the same temp on both sides of the thermostat, so thats opening. But the bottom rad hose barely gets warm when the top hose and top of rad are nice and hot. They both feel firm like there is pressure inside so the water pump should not be defective. The heater hoses are about the same temp as the engine coolant temp. The symptoms lead me to think there is a clog maybe. Either in the rad or the engine( I hope not the engine!) Here are my questions
1. Is there a way to easily test the engine for blocked coolant passages?
2. Also easy way to test the rad without taking it out?
3. If the thermostat stays open, wouldnt that also keep the thermosensor from turning the fan on, since the coolant never has a chance to heat up to the 189 degrees it needs to turn on?

lol I've been thinking about this like night and day I think Im starting to over analyze it! Lets unravel this mystery!

[ghettogeddy]

well id say pull the thermo stat and replace it couldn't cost more then 10 bucks to do the job
as for a rad test id say drain the system pull the top and bottom rad hoses and stick a garden hose in the top on and run it through for a bit

[88Accord-DX]

If your serious about that radiator, there isn't no easy way out on checking it's flow rate. To do it right, yank the radiator out & take it to a radiator shop. Have them check it's flow rate, it could be clogged up a little. The flow rate is somewhere around 18 gallons per minute.
(edit) I had to re-read your problem. Sounds like you need a new thermostat. If you want to see if the fan works, jump the wires to the thermosensor with ignition switch on. If the fan runs, their ok. I'd have the radiator tested for flow too.
To test the thermosensor, need to put it in water with thermometer. Should have continuity at around 200 degrees fairenheight.

[russiankid]

Isn't the lower radiator hose suppose to be cold and the upper one has to be hot?

[snoopyloopy]

maybe it's time for a koyo. ~$100 off ebay to your door.

[sunofogun]

Well im pretty sure its a clog somewhere I'm gonna try a back flush and see what happens. I dont know what the temp of the bottom hose is supposed to be? I know the fan works becuase I use the AC command to turn the fan on. I replaced the thermosensor last year, and I just tested the wires going to it after the overheat. If my thermostat was bad, why would the coolant be the same temp on either side of it? Wouldnt it keep increasing on the engine side, but not transfer over to the hose side?

[LX-incredible]

The thermostat could be flowing 1/2 or even 1/4 of the required flow to cool the engine, this would cause both sides to be hot. The radiator can cool that small amount before it gets to the sensor, without the fan. Replace the thermostat, it's cheap and easy.

[sunofogun]

Yeah true, but the upper rad hose is pretty damn firm with pressure, which is leading me to believe something is stopping its flow in the radiator. When the engine is warmed up, the top hose is nice n hot and real firm, firmer than normal I think, and the bottom hose is barely warm and easier to squeeze. On friday Im going to run some water through it and if it doesnt come out too nice im gonna replace it , the fins on it are all mussed up anyway! lol

Question: does anyone know if it will hurt the water pump, running the car with a clogged radiator? I know I shouldnt be driving it to be safe, but I just sold my Mx6 so now I only have one car- sux!! I knew as soon as I sold it the Honda would finally break down, first time ever!

[LX-incredible]

The firmness is probably from the coolant wanting to turn to steam. It really takes A LOT of deposits to clog a radiator. It shouldn't hurt the pump, but it will hurt the engine.

[sunofogun]

Well good news I sucked it up and drove without the A/C command on and when I got done driving... the fans came on!! Hallelujah, so I guess everything is ok. One question though, before, only the cooling fan came on. Now both fans come on(condenser and cooling fans). Is that how its supposed to be? And they stay on for like 2 minutes? I guess my rad cap has been bad since I got the car so everything I compare to how it used to be may be wrong.

[LX-incredible]

From what I gather the sensor on the bottom of the radiator turns on the main fan when it is hot. If the car starts to overheat the ECU turns on both of them as a safety thing.

[sunofogun]

Damn so why isnt it turning on !!! uggh

[dlr1989]

You have probably already done this, but just in case. Have you tried to bleed any air out of the system. This sounds like what mine did when I had an air lock.

[TWOLOUDNPROUD]

have you check the fan control box i have had one bad before on the LX-i it under the passenger seat i dont know where it is on a LX

[russiankid]

have you check the fan control box i have had one bad before on the LX-i it under the passenger seat i dont know where it is on a LX
I think it is in the same spot. I know there was some box under my seat in the LX, had a wire harness hooked up to it, but i have no clue on what it is.

[sunofogun]

what exactly does the fan control box do? This is so weird! Before just the main fan would come on after I idle for a bit and then shut off. Now the engine and the top hose seem hotter than they used to and both fans turn on for like 1 to 2 minutes. When it overheated, the fans werent running at all. Actually i just thought about the bleeding, I haven't done it since it overheated and released coolant out the reservoir. Possible theres some air in there. But still, why doesnt the main fan come on and do its regular routine? Normally i would check the thermosensor, but I just replaced it a year ago and I serisously doubt its gone bad already.

[MessyHonda]

Normally i would check the thermosensor, but I just replaced it a year ago and I serisously doubt its gone bad already.


did you get a honda one?

[shepherd79]

it is very simple.
replace the termorstat with honda OEM one. get it from honda. it is a lot better quality that someother ones outthere.

2. back flush the radiator and whole engine to make sure you don't have any clogs.

3. make sure you bleed the system.

you can also take to radiator shop and let them dyno flow it and see if it is cloged or not, but i don't think it is.

if it happens again, under passenger seat there is a fan control module, you may have to replace that.

PS. top hose should be hot and bottom radiator hose should be cold. that is how you know that radiator is doing its job.

[sunofogun]

Well, I replaced the thermostat and backflushed the system. The water pump seems to be working just not really making that much pressure. Maybe thats the design. Both cooling fans turn on after a while, which im starting to think is the way its supposed to be. I have a Honda shop manual and the one wiring diagram shows the two fans wired in parallel. I also do not have a fan control module.So I guess the way it was running before was wrong!! Haha, well see what happens in the summertime when I'm sitting in Philly traffic!

[synikil]

I just bought a 86 Accord LX. Both the cooling fans turn on when the relay kicks in. I have never seen just one turn on. When I press the AC button it lights up but nothing happens. I think it's low on freon and that is preventing it from turning on. When I feel my upper radiator hose it's hot but i can squeeze but it almost feels empy. I wonder if that is because the thermostat is just closed at that time or what. Does your upper hose feel soft too?