Just replaced the radiator because it had the typical hairline crack in the top plastic. Also replaced the thermostat while I had everything drained. Filled everything back up and ran the car to operating temp.

Fan doesn't come on. Jumped the fan itself to the battery, works. Unplugged the coolant fan switch, turned the key to II position, jumped the fan switch connector and the fan ran. So I'm under the assumption the switch is bad?

In the middle of the bleed process. Front of car on jackstands but will elevate higher to see if its possibly just air..

Where is RonJ when you need him?

 

Possibly there is still trapped air in the system. Bleed the system with the heater selector on hot setting, no need to run the blower. Remove radiator cap. If coolant still boils and fan dont kick in, check continuity of thermo switch. If it remains open when coolant is hot, replace the thermo switch.

 

The only thing that comes to mind for me, and from my past experiences would be for you to check the main coolant sensor, closest to the upper rad hose. Mine went faulty on me, I went to a Junk Yard and replaced it for 3 bux. This caused my rad fan to never kick on.

 

If everything was working before the radiator fix I'd try to keep bleeding it further.

 

using an ohmeter with an audible continuity tester. I'd be testing the thermo while it is hot. If i get an audible tone that means it is good, correct?

Im not entirely sure the fan has been working.

 

If you jump the fan switch connector with a paper clip does the fan run? If so replace the fan switch, they're only about $8. I had the same situation on my 96 and I replaced the switch and all was well.

 

Fan runs when jumped to the battery. And when the fan switch connector is jumped.

P.S. $8 where? haha.

 

Oops a little more than I remember but with the coupon code you can get it down to around $20 if you pick up locally
http://m.advanceautoparts.com/mt/sho...ing+fan+switch

 

Heh. Good thing for me I work there.. Lol. I just dont want to throw more parts at it. Piece of mind, sure. But at the expense of all the fun money.

 

Yes.
The coolant needs to get at least 95 degrees C before the switch close.

 

Must be a bad thermo switch then. Ran the car for half an hour with the radiator cap off and on a hillside, nose up. Way up. Only the slightest few bubbles, nothing major.

Turned the car off and tested the thermo switch itself with a continuity tester while still hot. No continuity. Will be picking one up from work today.

Thanks for all the help Axis11 and HondaPartsHero. Most appreciated. Will report back soon.

 

Did you turned on the heater while bleeding the system?

 

yep heater was turned all the way to hot.

 

Does the engine overheat? If not, there may be nothing to worry about.

In cold weather, the radiator may not run or may run infrequently. Civic engines tend to run on the cold side.

 

the gauge has never indicated an overheating issue. Nor has the car ever ran rough. There is smoke coming out of the exhaust now though.

As does the coolant rise up and over the top of the radiator without the cap on and revving the engine.

 

Coolant does come out of the radiator with the cap off due to expansion and formation of bubbles. You need to see steam starting to rise before the thermo switch close(about 95 *C). You may need to rev the engine higher than idle and cover the front grilles to make the engine reach operating temperature faster. are there bubbles coming out of the radiator continuously?

 

no bubbles, no overheating, going to install new thermo-switch tonight, will rebleed the cooling system. Will also check for bubbles, leaks, fan operation, etc. And run the car around for a while then post back if I run into any problems.

Its either bad rings or HG i think. So ill be taking it to a friends garage to do comression/leakdown testing. Either way, head has to come off..

 

Okay so installed the new thermo-switch. Both fans run if I kick the A/C on. But the damn lower radiator hose is ice cold. Had the car jacked up in the front and tried bleeding the cooling system. Ran car for a solid half hour. No fan, no overheating. Will put the car on the hillside in the morning. Its gotta be an air pocket. Or a damn fail of a thermostat..

 

The radiator and condenser fans are separate circuits, so only the condenser fan should run continuously when the A/C is on. This suggests that somebody tampered with the wires of the radiator fan circuit and spliced them into the condenser fan circuit. You need to fix this issue.

What is the outside temperature where you live?

 

Automatic trans or manual 5 speed?

Dont go throwing parts randomly. The thermostat will only start to open at about 85*C. Below that, its closed and no coolant flow,one hose will be cold. Let the car heat up until you see steam come out or the gauge climbs higher than half. If none of those two things happen, you are fine. There is nothing to fix.

 

@Ron its all original wiring. Car was bought from an older couple. I was under the assumption that the radiator fan should kick on even if it's for a split second if the AC is turned on. Outside temp is in the 30-40s. Even if I have it revved or idling for a half hour the radiator fan never kicks on and the lower hose is never remotely warm when compared to the top hose.

Maybe im just paranoid but id rather not crack another radiator so id like to get this figured out. Everyone throws different info at me.

@axis its a five speed. Gauge has never went above half. Even when the top tank of the radiator cracked.

 

The A/C and radiator fans of our Civics are completely different circuits and under separate controls. It's possible that the A/C and radiator fans could turn on at the same time time, but this would just be coincidence. If your radiator fan always runs whenever the A/C is turned on, then there is a problem with the wires.

At temperatures around 30-40F, the radiator fan of our Civic engines will rarely run.

If you short the 2 terminals of the unplugged radiator fan switch connector on the thermostat housing, does the radiator fan run continuously when the key is turned from off to ON(II)?

 

I did put a new fan switch in because I haven't heard the fan run in forever. I think I saw the fan kick on once after I put the new switch in.

My question now though is.. on the SOHC models, does the lower radiator hose ever get warm? The top hose gets hot, the lower is always ice cold.

From what I could tell from reading is that the sohc pushes hot water into the top radiator hose from the block. Whereas the dohc pushes hot water out the lower hose?

 

The lower radiator hose will get hot after the thermostat opens - both SOHC and DOHC.

 

Soooo if the lower hose never gets hot the thermostat isn't opening. Which is why I took my brand new thermostat back out of the housing, threw it in a pot of water and brought it up to temp. And it opened when it should have. This is why I am lost.