Car: 1999 Honda Civic SI
Motor: B16A2
No modifications

Issue: Coolant leaking, radiator fan not kicking on

Steps already taken:

Fan relays tested: good
Fan tested: good
Radiator - replaced (new from OReily's)
Radiator Cap 1.1bar - replaced (new)
Thermostat- replaced (new)
Water temp sensor tested: good
Upper/Lower Hoses tested for leaks: NO LEAKS


Fan relays and fan from 99 Honda Civic were tested in a running 99 Integra LS. Relays good, fan good. Water temp sensor swap tested in 90 Honda Accord, temp sensor good.

Fan relays and fan from 99 Integra LS swapped in to 99 Honda Civic, fan not running when engine up to temps. 99 Honda Civic Temperature gauge in cluster @ 1/3-1/2.

Honda Civic not overheating, however, coolant overflowing in to resevoir tank. Coolant has been drained and refilled numerous times. No apparent air pockets in cooling system. Warm air is passing in to cabin as it should.

Radiator, cap, and thermostat were replaced last night. Coolant still overflowing. Lower hose - cool, upper hose - warm.

I'm out of ideas what to do next. Any help, suggestions, ideas? Anyone?

 

Headgasket. Check that.

 

So basically you are getting too much coolant into the overflow?

You said fan not turning off in the orig post??? or did you mean not turning on?

 

Yes, too much coolant in to overflow reservoir tank, and overflowing. The fan does not turn on when engine is hot.

 

Did you test the fan switch on the thermostat housing?

When you run the car with the radiator cap off, do you see excessive bubbling?

 

headgasket.

 

Yes, the fan switch on the thermostat housing was tested. The fan switch from the 99 Honda Civic works when tested on the other cars.

The car was running with the radiator cap off, coolant seemed normal, no excessive bubbling.

 

When you are running the car can you see the coolant overflowing into the overfill tank?

Check your car for this:

http://www.tegger.com/hondafaq/tsb/civic/x00-025e.pdf

 

Thanks for the info.. I'll check this when I get home later. Let me know if you think of anything else.

 

update.. did some more testing last night. Water temperature sensor unplugged and now has a CEL code 6. Plugged sensor back in, reset ecu, CEL not going away. Tested the single-wire coolant temp sensor (under distributor), test results sensor is fine.

Also blead coolant system in process of removing sensors and checked overflow reservoir cap (see above pdf link).

Ran the car for a good 30-45 minutes with radiator cap open. Fan does not come on, however, coolant in radiator starts to boil over.

I'm starting to fear it's the headgasket.

 

1. Compression test.
2.Then headgasket.

 

Sounds like a headgasket to me. Was the car ever overheated? How many miles are on it?

 

The fan should come on no matter what, if you jumped the connector and tried another fan switch, you didn't put in the old fan switch did you?

Just to be clear you jumped your fan to make sure it does turn on? I think you said you tried your switch on another car?

What is the temp on gauge show?? (this never 100% accurate but gives you an idea)

Do a block test, simple to do to see if you have any exhaust gases in there.

 

I will get a compression gauge and test the compression as well. The motor was overheated once from lack of coolant. It must have boiled out in to the overflow reservoir because he said the radiator was dry. He said he noticed the temperature gauge at H and turned the motor off. He's usually pretty good about noticing stuff but I'm not sure how long before he noticed it.

The temp on the gauge shows no more than 1/2. The switch, sensors, fan, and relays were tested on a working Integra, no issues with any of the components. The switch was tested again on an Accord, worked fine there also. So I ruled out those components by taking the switch, sensors, fan, and relays from the integra and put them in the Civic, but nothing worked, so we put everything back.

 

Make sure you physically check the fan working not just the relay and switch.

Unplug the harness at the thermostat, take a paperclip bend it like a U insert each end into the harness plug, turn the key to position 2 and see if it comes on. Did you do that?

 

Hope the head is not warped.

 

I tested the fan, relays, switch, and sensors in a different car and fan works. Everything from the Civic works in the Integra as it should. Took everything from the Integra and put in to the Civic, nothing worked. I'll double check the harness plug and jump it as you mentioned.

I hope the head isn't warped either. Will have to take the head off and check after the first of the year. I'm out of ideas.

 

Testing your stuff in other car's will not work with fan coming on since if there is a wiring issue you will not be able to tell, test the fan as I stated.

Then do a pressure test and a block test, don't just pull the head, test first. You can rent these tools.

 

Sounds like the fan switch wiring is screwed up/getting old (happened to mine, overheated the motor and blew the head gasket)
Or the fan motor is no good
In any case, the headgasket is almost certainly leaking exhaust gas into the coolant and overflowing it
Good luck!

 

I jumped the fan switch plug and the fan comes one and the fan switch was also tested on a different car, and works. Therefore I've eliminated the wiring and the switch out.

I'm going to try to re-bleed the system and rent a block tester and a compression gauge to test the motor to see if I can't find anything else before removing the cylinder head. Thanks for all the input.

 

why not check if there is exhaust gas in the coolant autozone has a cheap tool for that u can buy

 

He said is going to do it, that is a block tester.

 

my bad didnt see it