2006+ Honda Civic Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
I am at my wit’s end regarding an overheating issue with my son’s 2010 Civic DX VP.
Initially, it was losing water and overheating. We could not determine where it was losing it from.

There were no puddles anywhere or wet areas noticeable.
A cracked head or blown head gasket came to mind, but there is no water in the oil, and the engine runs great.
Realizing that it may be a leak that only occurs when the engine is warm, we started looking elsewhere and found a faulty lower seam on the radiator.

At the same time we found the radiator fan to be broken.
We replaced both the fan and the radiator, as well as the hoses and cap.
The issue seemed to be fixed, although it may have just been short drives masking the problem.

After about a week, the overheating returned, we then replaced the thermostat and it was still overheating.
The radiator fan would only come on with the A/C fan when the engine was quite hot.

My son took it to AAA and they said they thought it was a faulty ECM.

Before doing that I tested and verified that all the relays were good (not just the fan related ones), as well as the fan control switch in the fuse box and all the fuses.
Then I replaced the ECM and had it reprogrammed.

The car continued to overheat.
At this point about the only thing left that I could think of was the #2 ECT sensor, so I replaced that, too.

I took the car on an extended drive (two trips of ~90 minutes each) with my Innova unit hooked up monitoring live ECT data.

The ECT ran at about 217-232 most of the time, but would run up to 244 on occasion and once hit 250, at which time I had to take evasive action.
The fan comes on religiously at high temperature with the A/C fan, but never by itself.

I don’t know where to go from here. I know the fan supposedly has a low and high speed and evidently is not running in low speed. Is this a fan issue or a circuit issue? Any other ideas or thoughts??


Thanks in advance.
 

·
Super Moderator
Joined
·
7,124 Posts
That 217~232.
I take it you're referring to 217°F~232°F

This would be 102°C~111°C which IIRC was the rough operating temp for the civic

244°F is 117°C and at this point any engine is not happy 250°F is 120°C and that is the temp of when engines decide to start dying.

Have you had a pressure test done on the system?

I would hazard a guess you have a bad head gasket.
Start the car and remove the radiator cap, if the coolant is bubbling, you have a blown head gasket.

Also look for white smoke from the tail pipe.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #3
Yes, I believe my son had a pressure test done and it was negative.


I don't know if there is any connection, but in the wacky world of modern car electronics there may be.
The fuel gauge sometimes disappears and sometimes it reverses, i.e. blocks light up from full to some point toward empty.
Also, as an added note:
Yesterday I recharged the freon in the A/C system (was at zero). Now both fans come on when the engine gets warm (earlier than prior); however the radiator fan still never comes on solo.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #4
The car still overheats. The radiator fan NEVER comes on by itself. It should, shouldn't it?? However, it does come on in conjunction with the other fan when the engine gets too warm or the A/C is on, as it should. The only thing I haven't replaced is the temperature sensor on the head itself. I don't think that one has anything to do with the radiator fan.
Since rtd's resistance goes up as temperature goes up, shouldn't disconnecting the lower sensor on the radiator make the fan run? I tried thaat and it doesn't. Also tried jumpering the wires; also no go.
I am looking for ideas, please. Especially as to why the fan doesn't run solo. I think that is the root of the overheating issue.
 

·
Premium Member
Joined
·
2,227 Posts
My son took it to AAA and they said they thought it was a faulty ECM.

The ECT ran at about 217-232 most of the time
Judging by the "Triple A" and Farenheit, this is an US Civic? - Not a problem, as it still shares an engine with the rest of the market - R18, if you've got the 1.8 version.

A good resource for you, with troubleshooting guides can be found here: Funkimunks ngESM (The EU Honda service manual)

I'd suggest checking in here.

I'd also reccomend getting an OBD2 to set up live monitoring for your engine temperatures to see what's going on; The included temperature gauge will only show you
Cold -> OK -> Hot! -> Overheating
So an OBD Readout will be a bit more revealing.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #6
The readings I mentioned in the first post were from live data on an OBD2 scanner. I will look at that site.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #9
This is a USA Honda 2010 Civic DX .
AAA is the American Automobile Association. They have very good service departments, amongst numerous other services. Let me know if you need any further information.
 

·
Premium Member
Joined
·
1,212 Posts
if the head gasket is leaking into the exhaust and not into a water ways you will see very little or no oil in water mixing ( mayo as we like to call it ) what it will do is stop the coolant from flowing causing the engine to overheat

another tell tale sign is the radiator doesn't get as hot as it should or has cold patches because of the lack of coolant flow.
if you accelerate quite hard does the temp climb quite rapidly and start to cool down as you de accelerate / coast ?

there's only a few things that can cause an engine to overheat

head gasket
thermostat stuck closed
coolant or the lack of it or not flowing around the system either because of a broken water pump or the system being pressurised

even if the fans did not work there should still be enough airflow whilst driving to keep the engine from overheating as long as you are not idle for any length of time
if the fans are coming on regardless of which ones or in what order it should still be enough to cool the engine especially if they are coming on at high speed

take the top off the expansion tank start the engine and see if there is water flowing through the tank at idle
get somebody to sit in the car and raise the revs 1000 rpm at a time and watch the expansion tank to see if the water still flows and as already mentioned watch for bubbles
do this when the engine is cold so you don't scald yourself
if the coolant stops flowing or you see an unhealthy amount of bubbles there is pressure in the system and the only place the pressure can come from is the head gasket
 

·
Registered
Joined
·
10 Posts
Discussion Starter #11
What is the method by which the fan switches from low speed to high speed and when does it do each?
 

·
Premium Member
Joined
·
1,212 Posts
What is the method by which the fan switches from low speed to high speed and when does it do each?
some time ago i tried to work this out but without any form of documentation ( the honda manual doesn't go into enough detail ) it's almost impossible to work out.
looking at the wiring diagram for the relays this is the best i could come up with

the coolant fan should kick in around 96 degrees c

as far as i can make out this is what the 2 radiator fans should do

there are 3 relays that control the 2 fans

relay no 1 controls the coolant fan ( normally open )
relay no 2 controls the AC fan ( normally open )
relay no 3 switches the fans from half to full speed depending on the state of the other 2 relays

if relay no 1 is closed and the AC is off both fans should do nothing or spin at half speed depending on engine temp

if relay no 2 is closed and no 1 is open the AC fan should spin at full speed and the coolant fan should be still
relay no 3 is controlled by the same signal as relay no 2 so changes state when the ac relay closes
relay no 3 has 2 states
the idle state is shorting both fans together via the positive wire on the AC fan and the negative wire on the coolant fan so they spin at half speed
the active state is to isolate the ac fan from the coolant fan and ground the coolant fan to enable it to spin at full speed when relay no 1 ( coolant fan relay ) is closed
if relay no 1 ( coolant fan relay ) is open and the AC relay is closed meaning the 3rd relay will also be active isolating the AC fan from the coolant fan and grounding the coolant fan the coolant fan should be idle and the AC fan should spin at full speed

if all three relays are active both fans spin at full speed

with me so far

this is how i think it all works and this is what is happening

start car from cold AC off no fans spin which i think is normal
switch AC on both fans spin at half speed in time with the engaging and disengaging of the AC clutch
as far as i can work it out this isn't what should be happening and i'm pretty sure what should happen or what did happen is the coolant fan would be idle and the AC fan spins at full speed in time with the engaging / disengaging of the AC clutch while the engine is cold

i can make this happen by changing the state of relay no 3 which basically isolates the coolant fan from the AC fan and grounds the Coolant fan
in other words by changing the state of no 3 relay the fans are now independent form each other and when their relevant relays close spin at full speed which in my way of thinking is how they should behave
both fans spinning at half speed is only possible if the AC relay is open ( AC off ) which would be normal if the engine was up to working temperature

as far as i can tell whats causing this is a non serviceable relay buried in the middle of the under bonnet fuse box
there are only 2 serviceable relays within the box, one is the AC clutch relay and the other is what i have labelled relay no 3 which is the other relay you can see sat next to the AC clutch relay better known as the fan control relay
the coolant fan relay ( relay no 1 ) and the AC fan relay ( relay no 2 ) are buried inside the under bonnet fuse box

i'm still no wiser as to when each fan should kick in and at what speed :(

good luck...
 

·
Registered
Joined
·
10 Posts
Discussion Starter #13
Awesome response!!
That is pretty much the interpretation I had of the circuit, as well. However, the operating temperature is new information; well appreciated.
To me, it almost seems as though the (#3) fan control relay operates opposite of logic. Probably just me. Anyway, by what you came up with and the way I see it, the coolant fan never runs strictly by itself. That blows me away. I would think it would run at low speed to maintain happiness and kick to high speed or perhaps both fans on low speed when temp gets high; then both on high for A/C. But, I am no Honda circuit designer, so...
Anyway, on my civic, all three of these relays are accessible in the under-hood (bonnet) fuse box, as well as the PGM-FI sub-relay. I have tested them all and they all function properly with/without voltage.
I am currently running the car with A/C on to see what happens when the compressor cycles.
 

·
Premium Member
Joined
·
1,212 Posts
the fuse box in the European mk8 civic looks like this



it looks like the US civic fuse box is different
 

·
Premium Member
Joined
·
87 Posts
Interestingly Eric O. of SMA posted a diagnostic video of the 3 relay cooling system in an Honda Odyssey yesterday.


From the video I would say having access to good wiring diagram is a must.
 

·
Premium Member
Joined
·
1,212 Posts
Interestingly Eric O. of SMA posted a diagnostic video of the 3 relay cooling system in an Honda Odyssey yesterday.

Honda Odyssey : One Cooling Fan Works On High / Both Work On Low? - YouTube

From the video I would say having access to good wiring diagram is a must.
interesting video thanks for sharing

i have the diagram for the mk 8 civic ( Euro version ) and there pretty much the same as the one in the video and did pretty much the same sort of diagnostic tracing but what isn't mentioned is there are 2 signal feeds ( one for coolant and one for AC ) to the fan relays which seem to be linked via the relay coils in one way or another
in the case of the video the end result was a blown fuse but if there is no blown fuses the symptoms can be the same if one of the relays packs in.
in the us version fuse box the relays are accessible so can be diagnosed / changed but in the Euro version fusebox 2 of the relays are internal and non serviceable unless you pull the fusebox apart and unsolder them to replace
the tricky bit is trying to work out whats going on with the fan sequences to get an understanding of how the should behave, it's not an easy task :(
 

·
Premium Member
Joined
·
87 Posts
Thanks for the detailed explanation, I hope I never run into this problem. If I come across anything that might be useful I will post it up.
 

·
Registered
Joined
·
186 Posts
Funny enough I queried with the dealer on my last visit why my engine fans never seemed to come on in my mk9. The mechanic jumped in, switched on the A/C, set the temp to min and the fans came on and said they were working normally. Mine has climate control though if that makes any difference.
 
1 - 18 of 18 Posts
Top