i have a 93 hatch and before i swapped in a b18b, the radiator fan worked fine. after the swap, when doing the first warm up, the radiator fan never came on. a little after 15 minutes, the radiator would start steaming from the fins. it is not a bad or leaking radiator. i flushed it. i tested the thermostat and it is good, so is the cap. i put the relay in my friend's civic for a test and it is good. i checked all associated fuses and they are good. i jumped the fan from the battery and it is fine. i wired a switch to the cabin and that is how i have been operating the cooling. i did ditch all my a/c and blower accesories including the blower unit harness, but i believe the a/c fan is on a separate circuit than the radiator fan. i have not "checked for voltage" because i don't know exactly what to check. if anybody can help on this i would be greatful because i am tired of "switching" my fan on when i am stopped or when the temp needle pegs. i have done a few swaps and this has never happened. i doubt it has ever happened to anyone else because i have never heard of this problem. if anyone has any ideas, please reply. thanks.

 

Air bubble in the system, bleed it off. There's probably a lot of air. It's happened to me many a times.

 

how are you supposed to completely bleed it and rid the air. i took out my heater core and used heater bypass plugs, but that shouldn't matter should it? when i open the bleed bolt, i try and fill the coolant and try and wait for the bubble free stream but it will steam up before i see no bubbles. should i just keep waiting and let it steam real bad? what is a normal warm up time anyway?...it should come on within 20 minutes shouldn't it? i haven't let it run that long because i usually shut her off when i see that steam coming out all over the place. how do i expel all the bubbles though? thanks Aj.

 

Bleed the system on a cold engine. Once you get a steady stream from the bleeder valve, close it and fill the rad all the way to the top of the filler neck. Close the cap and warm up the engine to normal operating temp.

But the only sure way for an air free cooling system is to fill it using a professional system that pumps out all the air out of the system BEFORE filling it with coolant. This way the system is a complete vacuum when the coolant is pumped in.

As for the fan, did you check the fan thermoswitch? It's usually located in the bottom of radiator (i'm not sure about G5 Civics).

 

thanks, i have wondered where the fan thermoswitch is exactly. i can't locate it and am still trying. i will just take my time. this is probably something very simple that i'm not seeing. i won't take it to a shop i'll tell you that much. it's just because i hate them to death. i wish i knew a good mech.

 

I'm not 100% positive..but I think the thermo switch is right at the thermostat housing...at least that is where it is on my GSR.

 

i could probably use a civic thermoswitch in the b18, do you think so? i pulled one that i know is good out of a d16z which was pulled for a b18c1 just last week. i haven't changed them yet. i am going to try. thanks all.