Civic 95 Lx impossible overheating issue.

[Clark Kent]

Hi everybody.

My civic 95 try to kill me with this imposible issue.
It overheat when idle for to long,or in city driving,or a steep long hill,especialy when the heater fan is not on.

If the cabin fan is on,no overheating.How it manifest the problem: temperature gage usualy stays below half of the scale.No mather what,before,and also to my other civic 93 does not climb up over a third of the scale.In this case,temperature go over half,close to 3 quarter of the scale and only then the fan swich on the termostat housing kik in and start the radiator fan.At this point changed all temp.relatet semsors.(sending unit under distributor,temp.ECM sensor under distributor,temp.swich on termostat housing-twice last time with a OEm from the dealer,intake temp.sensor behind the intake manifold,).Also replaced water pump,3 thermostats, checked gas leak in coolant,got to extreme and decided to change the head gasket(just to be shure),same thing.In long run everything looks ok,in city driving temp.rise over half.Checked all wiries,replaced ECM,dsame thing . It seems to me that the fan switch on the thermostat housing is the last resort to turn the fan on. Question is: does the ECM turn the fan on also? In what conditions? Checked wire on pin12 on A connector.If touched to ground ,it turn the fan on.I end up soldering a wire inside the ECM puled out and connected to the black-yellow wire directly to be sure that it work.Same thing all over.Any suggestions?

 

[Clark Kent]

Stock engine?

Properly bleed the cooling system, and then go from there.

Yes stock engine.Bleed cooling system multiple times.No bubbles, no gases,no overflow.Level of coolant stay the same.No loses.Still problem persist.Does ECU start the fan or the switch on thermostat housing.Which one is the first?

 

[Clark Kent]

Lift front of the car on car ramps so the front stay higher .Lose the 12mm air bleed screw on upper hose close to the head.Also open one of the small hose going to idle control valve.Opened cabin heater control to full and pour coolant in the system until no bubble was coming from both openings. Fill also the tall funnel I have mounted in radiator cap location,start the engine and let it run for at least 30min.until no bubbles come from the system at any rpm. Did this few times. Still same result.After warm up radiator fan starts after half indication of the gauge. And since thermostat housing switch is the primary fan control ,what the wire going to ECU on pin 12 conn.A does?What is the purpose of it?

 

[Clark Kent]

Did it remain open until no air was released?



This^ should NOT have been done as it allows air to enter the cooling system.



The fan should start to run BEFORE the temp gauge needle reads above halfway. Repeat the bleed as you described (with fan turning on twice), except do NOT disconnect the IACV coolant hose.



In theory, it is supposed to turn on the radiator fan; however, the service manual does not describe the conditions in which the ECU would turn on the fan.

To boofoo: What is the problem with the hose for the IACV? I replaced thermostat 3-4 times.At that poin when you open the thermostat housing,cooland level in the engine is at half of the block level.Basicaly you lose at least half of the entire coolant.I have a funel adapted to radiator cap aprox.10 inch tall.Can you imagine the level when I fill the funel with coolant? Is way above everything in engine compartment.Reason for me to disconnect temporary that hose was to be shure that there is no air in it.No air is allow to go in, since colant burst out due to high level in the funel. And again I did this multiple times. It looks to me that I have 2 different zone temperature,even with the thermostat completely open.One in the head area,one in thermostat housing area. And during colant replacement the system remain open more then 45 min.No air was coming out at any rpm.