96 Civic ex 1.6L auto trans. 177k miles. Two separate fans, the A/C fan works with A/C on, the radiator fan will not come on. Fan is good, jumped the switch, fan runs. I just replace head gasket, thermostat, coolant temp sensor, coolant fan switch (water pump a year ago)
Temp gauge goes up to hot, hasn't gone all the way yet but pretty close when at a stop. After I start driving, the needle drops back down to the normal range. What gives?

 

Test drive with switch jumped so fan runs all the time. If it does not overheat, the switch may not be working or the harness plug is bad and not making contact with the switch.

 

Did you already bleed the system?

 

Bleed the system

 

https://honda-tech.com/forums/honda-.../#post39830585

 

I lifted the front end on blocks, ran the fan on full heat for about 20 mins after I put the engine back together in the beginning.

 

Give details.

Was radiator cap loose?

Did you keep the radiator and reservoir topped off with coolant during the entire procedure?

Did the fan turn on twice?

Repeat the bleed if you did not follow the instructions.

 

I'm fixn to be changing both my sensors soon (thermos sensor, temp sensor).. My car started to over heat too..no leakage, radiator was still full

 

It takes longer to bleed, not 20 minutes. You need to give it time to kick on the radiator fan. That will tell that the thermostat has opened up.

 

mine was over heating, 99 dx hatch with ac as well, was gonna change the fan switch but decided to check the fuse under the hood, sure as **** the fuse was blown. changed the fuse and no more overheating. try that?

 

it the block relay from under the hood?

 

Check fan relay and fan fuse. With all those new parts I would just go ahead and buy a new radiator fan assembly

 

So...when you bypass the fan switch, the fan turns on and no overheating, when you drive, no over heating. Even though you just said you changed the fan switch, do you still have the old one? Can you swap it back in and see if you might just have a bad switch.

 

Fan relay is fine if he said he jumped it.

 

Thanks Tony, yes the fan is getting power, relays and fuse good. I suppose it could be a bad (new) fan switch. Is there a away to test the switch off the car?

 

Using a meter and measuring continuity across the two terminals, you can heat up the contact surface with a heat gun, simulating the coolant. When the switch closes, the two terminals should "close" and complete the circuit.

 

Which switch for the coolant did you replace, the one on the cylinder head or the one on the thermostat housing

 

This.

Hondas have redundancy. Two temp sensors, two ways for the fan to turn on.

And maybe it's just where I live, but unless you're in a hot place in a lot of slow traffic the fan doesn't do much, it's basically useless past like 15-20km/h or even slower, the wind being forced into the car from your speed does more than the fan at thst point.

Thus, if you're overheating I'd be less worried about the fan and more worried about what the root cause is, first. I drove sohc zc swapped ef without a fan for 6 months never noticed (whoever did the swap forgot the fan) until summer came and it overheated stuck in traffic.

Unless you really do live somewhere hot as ***** and sit stopped in traffic a lot and that's all but if it isn't, chances are you're still going to experience thermal run away until the root cause is solved, meaning the stock fan/rad can only do so much to shed heat BUT should be enough to avoid thermal runaway on a stock motor running properly in neaely any environment.

Tl/dr the fan sucks and doesn't do **** unless you're going slow or stopping a lot. If it doesn't overheat on the highway and only stopped, then worry about the fan. If it does, then worry about something else.

 

Can you show me the diagram that shows there are 2 sensors to activate the fan? I'd like to see that.

 

I was going to post the same thing. The fan only runs for about 30 seconds at a time. I've even monitored Temps with an IR thermometer to verify Temps under the hood. Fan barely runs at all because the car doesn't run very hot

I really like my $50 ebay silicon radiator hoses and heater hoses on all of my hondas. Silicon is suppose to last forever and the heater hoses always need to be replaced. I can't say that you're having that problem, but it is a great investment that is considered an upgrade and maintenance



I understood what he ment. Only 1 is for the fan, and one is for the ecu, and then the third one is for the gauge. If I'm remembering correctly the switch on the thermostat housing is for the fan switch

 

Just to add more confusing and useless information to this thread, the 99-00 D16Y8 has 4 coolant temp sensors.

 

Y U do dis? Lol

 

Educational?

 

I know I was kidding lol

 

I was kidding too.