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04 Civic EX Fans

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Old 08-05-2018
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04 Civic EX Fans

Hello all-
By no means am I mechanic but i do like to fix my car when it breaks down.

My car has had problems overheating when I am going slow (30mph or less) or when i get stuck in rush hour traffic. If i am on the thruway and doing 75 then I never have problems. I started with the basic diagnostics: relays and fuses. After that I tested both fan motors by hooking direct power up to them and they both started spinning. Looking at the front of the car I have two fans. The fan on the left i was told is the radiator fan which comes on when i turn on the AC and when the coolant reaches a certain temperature This fan was spinning when I hooked up the power too it but it was not spinning at full speed so i ordered a new fan. After doing several hours of tests on my car i realized the fan on the right never comes on and i have no idea what it is for.

1. can someone explain to me what the purpose of the 2 fans on my 04 Civic EX are? and also explain when they should actually kick on. Do they both kick on when i run the AC or does only the left fan kick on when AC is on. I have not been able to find an answer by reading through forums and watching good ol youtube.

2. another random question i have is i have lots of rust color found around the over flow of the radiator. is there any reason why i would have thsi rust color in my coolant overflow tank and all inside the radiator?

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Old 08-06-2018
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Re: 04 Civic EX Fans

#1 issue: I didn't read that you ever actually checked that the radiator level coolant is FULL.
Overflowing overflow bottle probably means blown head gasket.

BOTH radiator fans MUST run at the same time-- every time.
BOTH fans must run when the engine temperature requires them to run, and BOTH fans must run when the compressor is engaged. Each system can turn on the fans.

But that alone can't keep the engine from running hot if the radiator is low.



The rust color is probably from lack of correct antifreeze service...or similar neglect... Has someone been adding straight water instead of 50/50 mix?
That rust coating (and corrosion) can eat up the water pump and inhibit heat transfer through the radiator and heater cores.
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Old 08-06-2018
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Re: 04 Civic EX Fans

@ezone
#1-so one problem i had was that when the car was overheating i would have to manually add fluid to the radiator, after a while i started adding water due to the cost. I was never quite sure why my fluid kept on getting low because i didn't see any leaks. I thought it might be a head gasket but the oil color was normal when i changed it. after installing the fan on the left i had to remove the overflow bottle and found that on the bottom of the overflow tank there is a nipple that the rubber overflow tube connects too. there was a very small wire clamp around the rubber hose and when i filled the tank up to the minimum level and put the hose back on, i was able to see a very very slow leak. this makes sense that when the engine would get hot and the fluid would overflow to the tank that it would slowly lose it through the leak but then would then get sucked back into the radiator when it was cooling down. Also explains why i would only need to fill up the fluid every so often. I thought it was just the water being evaporated by the hot engine rather than it being a leak.

in regards to the rust color, I am going to do a full flush on the system. This is most likely due to the amount of water ive put in the system to keep it cool. hoping i didnt cause damage to the water pump!

lastly, only my left fan is turning on. So if the right fan is not turning on any idea on what could be the problem? ive tested the ohms and also connected direct power to the fan and it spins at a high RPM. I do not believe it is the fan so curious as to why the fan is not turning on.

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Old 08-06-2018
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Re: 04 Civic EX Fans

I thought it might be a head gasket but the
But you don't know what to look for. You won't find fluids mixing, or any of the usual stuff most people think to check....and it will pass most tests especially before the breach becomes major..

So fix your dribble, check the radiator and cap are good, flush/fill/burp system then keep a close watch on the system.
If it fills up or pukes out the reservoir and the radiator keeps going low, you have a serious problem.

but then would then get sucked back into the radiator when it was cooling down.
This will not occur if there is a leak that allows air in during light vacuum
This will not occur if the fluid level in the radiator is too low.
This will not occur when the head gasket is blown.
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Old 08-07-2018
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Re: 04 Civic EX Fans

thanks for all the advice on this.
Testing the head gasket will be my last option. Hoping it is a much cheaper route.

going back to the fans. you said that
BOTH radiator fans MUST run at the same time-- every time.
BOTH fans must run when the engine temperature requires them to run, and BOTH fans must run when the compressor is engaged. Each system can turn on the fans.


Is there any reason as to why the right fan is not working but the left fan does? I hooked up direct power to it and it works fine and the ohms on the fan also seem to be normal. I also tested to see if power was coming to that right fan and i found voltage.

Last edited by BillsMafia; 08-07-2018 at 09:11 AM. Reason: more to say
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Old 08-07-2018
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Re: 04 Civic EX Fans

Originally Posted by BillsMafia View Post
t
Is there any reason as to why the right fan is not working but the left fan does? I hooked up direct power to it and it works fine and the ohms on the fan also seem to be normal. I also tested to see if power was coming to that right fan and i found voltage.
Sure. Something is wrong. The fan motor works, so keep going.
You've got fuses, relays, and wiring to contend with.
I'd get my voltmeter and/or test light, a wiring diagram, and study so I understand how it works and what to test, then test accordingly to determine why it does not work. Then fix it.
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