I have 91 civic with swapped b20b. I have been driving it for last 2-3 months no problems with over heating. Today was a extra hot today as the weather is starting to get hot, and I noticed my car started to over heat.

-Thermostat is brand new
-Water pump is brand new
-radiator fan is working and coming on
-Brand new full-race half rad with 10" mishi slim fan( no shroud)
-Coolant levels seem okay

What is happening is when I start to drive the car is starts to over heat it almost got all the way to the red line so I shut my car off. Waited for a while then turned it on again. After driving for a few minutes it started to over heat and fluctuate. I then turned my heat on full blast and it stayed at normal operating temp. When i turn my heat off it starts to rise after a minute or so.

I also was city driving 40-60 kms/h when this was happening. Then it cools off when I stop driving.

When I am idling though my temperature drops back to normal (with my heat off). What can I do to try and correct my problem.

 

Put the stock fan back on or get a shroud. It makes all the difference. Did you bleed the system of air?

Continue to overheat that engine and you'll be looking at buying another one to replace it. That is, if you haven't already damaged it.

 

Yes, I may have to look at getting a shroud and I never over heated it I turned it right off as soon as I started seeing my temperature rising. I believe I bleed the system correctly I left the cap off and and let all the air bleed out and waited for no more bubbles.

 

All the sensors working correctly?

 

i bet you still got air bubbles in the system. Ive bought one of these and used it in all my cars. works great and not messy at all.

 

This is the main problem. The slim fan is only cooling the water 68% of the time at most, given a 14" square fin area and a 14" fan with a 5" dead spot under the motor. For all you know, the other times it was hot out your rad fan was running >90% of the time and juuust barely enough. Now it's hot and it's not enough.

 

So I checked my full-race half rad and there are not mount holes anywhere on that rad. The Mishimoto rad came with a zip tie kit. I don't see how I can mount a shroud anywhere unless I make something to mount a shroud, but I don't want to penetrate the radiator obviously. I borrowed my brothers Go pro and took some footage to show you what exactly my car was doing.


I skipped all the driving around in the video leading up to where the temp gauge started going high. Basically leading up to this point in the video I started my car warm it up for a minute. Drove around the city for say 8 minutes, then drove on the highway for a few minutes( with the temp gauge stable a bit under the half mark). After getting of the highway I came to a complete stop and put it in park. When I started to drive again is when the video starts from.

 

In this video you see my temp gauge go right up to the red. That's when I switched my heat on full blast and it went down to normal temperature. Then at around 2:30 I was about to get on the highway( I turned my heat off for the rest of the way home). I drove the highway than the same route around the my area then went home, and not once did my car temp gauge rise again.

 

Could I try to wire the fan to a switch I see a lot of people who do this. Or should this not be necessary?

 

Dumb idea.
I don't see how you don't have mounting locations on your rad. I have them on my GoAutoworks rad.
This video is private.

 

Sorry I corrected that please try and watch it again.



This my full-face half rad currently in my car with a 10" mishi fan mounted in the middle. You are right it is dumb that there are no mounting locations. The thing is though this was the only rad that was a direct fit with my full-race traction bar, with out having to do the ghetto lean or cut the webbing in my hood.

I tried re bleeding the system again today, took it around the block it eventually started to heat up again so I ran my heat and it cooled down. The weird thing I am noticing though is even with the heat it still seems like it kind of high its literally just below the half way point. But then when I stop get out my fan IS NOT running. Then it kicks it after a short while of idling. Should my fan not already be on right when I stop since the car is hot, and I am having to already cool it down by using my heater?

Could it be possible that the new thermostat I bought it defective?

So far here are my options I am currently looking at.

-Try replacing thermostat(maybe for a lower temp one?)
-Wire the rad fan to a switch like the previous owner had on his old setup
-By a bigger rad fan.
-Have pusher & puller fan

 

I dont know how the civics fan system is but on 2nd gen integras the condensor fan is on a seperate circuit that runs when the ac is on, or if oil temps reach higher than 225°F. Thats determined by the colant switch on back of the block. The rad fan switch is on the tstat and kicks on a 196-200°F.

Again not sure what normal is on a civic, but at 200F my gauge reads less than half, but more than 1/3 on the gauge.

If youre using the switch on back of the block to control the rad fan you might be making your fan kick on late.

Or maybe the tstat is defective (if its not oem it might be)

 

Well on my b20 the thermostat housing is on the back on the block, but I do not see how this would affect it over heating.

After looking over everything again it can not be my thermostat do to two reasons. The tstat is opening allowing coolant to flow through the engine because my lower & upper rad hose are around the same temperature after it warms up, and my rad fan kicks on.

It also seems after my car gets really hot my rad fan does not shut off so I know everything is working. When I stand in front of my car when its hot it burns my legs from the heat coming from the rad.

The only thing I can think off is my rad fan is most likely understand and not pushing enough cfm to pull all the heat away from the rad. That's why when I run my heat it's acting as a second radiator cooling the engine. ( The thing is the blower motor just went on my heater yesterday. It turns on and spins very very slow then stops and wont go again).

How do I go by wiring another fan into the circuit. Could I just splice the wires after the plug together so they both come on at the same time? Or should I wire it to a separate switch or something.