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Discussion Starter · #1 ·
As title says, 96 civic coupe. INTERMITTENT overheat doesn’t go above 3/4 of the gauge, not in the red. turning the heater on brings temps down. Things I have tried:

  • Block test, showed no exhaust gasses. No other signs of head gasket failure.
  • Replaced old radiator hose and radiator cap
  • Tightened other hoses
  • Bled coolant system
  • Replaced thermostat

Any guidance would be appreciated.
 

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BATSLOMAN GIVES NO FUCKS.
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clogged radiator
water pump failing
fan not kicking on
 
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Brokedick Millionaire
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If the temp gauge goes above the 1/2 way mark, you are over heating.

Verify the fan is coming on....
 

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The fact that running the heater brings the temp down, tells me the cooling system is pretty healthy and is at least not super dirty or clogged anywhere.

Like stated above my Bone, check that the fan is functioning. I like using a spare battery and wires to jump the fan to verify it is capable of working. Then start looking at wiring diagrams, figure out the method of triggering it.

Couple be as simple as the fan switch sensor being bad. Its mounted on the cylinder head under distributor if memory is correct. Single wire. Might even just ground it or something to test fans, dunno..

tech manuals are freely available, and in many locations online, find one! Best thing to have with any car for sure!
 

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BATSLOMAN GIVES NO FUCKS.
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The fact that running the heater brings the temp down, tells me the cooling system is pretty healthy and is at least not super dirty or clogged anywhere.

Like stated above my Bone, check that the fan is functioning. I like using a spare battery and wires to jump the fan to verify it is capable of working. Then start looking at wiring diagrams, figure out the method of triggering it.

Couple be as simple as the fan switch sensor being bad. Its mounted on the cylinder head under distributor if memory is correct. Single wire. Might even just ground it or something to test fans, dunno..

tech manuals are freely available, and in many locations online, find one! Best thing to have with any car for sure!

isn't the single wire for the temp gauge?

I thought the fan switch was on the thermostat housing
 

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Discussion Starter · #6 ·
clogged radiator
water pump failing
fan not kicking on
The fact that running the heater brings the temp down, tells me the cooling system is pretty healthy and is at least not super dirty or clogged anywhere.

Like stated above my Bone, check that the fan is functioning. I like using a spare battery and wires to jump the fan to verify it is capable of working. Then start looking at wiring diagrams, figure out the method of triggering it.

Couple be as simple as the fan switch sensor being bad. Its mounted on the cylinder head under distributor if memory is correct. Single wire. Might even just ground it or something to test fans, dunno..

tech manuals are freely available, and in many locations online, find one! Best thing to have with any car for sure!
Fan is definitely working, I’ve noticed the coolant is pushing into the reservoir very often which makes me think its a blockage somehow
 

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isn't the single wire for the temp gauge?

I thought the fan switch was on the thermostat housing
goddamnit, you are correct.

thermostat mounted fan switch, single pole for coolant temp
 
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pushing into the reservoir is normal under high temps and pressure. What you want to avoid, is it overfilling the reservoir.

Get it hot, witness the tank filling. Shut the engine down, and check on it every 15-30 minutes afterwards. Does the system reclaim the tank contents? or does the contents stay in the tank? Should always have some.


You cna very well have a headgasket starting to go, allwoing air to be forced into the cooling system. Doesnt necessarily need to expose enough combustion gases to fail a sniffer/blue bottle


What does the radaitor cap look like? ANy super shiny bits under the cap, indicating something is being stubborn adn rubbing? any debris? does it collapse with your finger strength?
 

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Discussion Starter · #9 ·
pushing into the reservoir is normal under high temps and pressure. What you want to avoid, is it overfilling the reservoir.

Get it hot, witness the tank filling. Shut the engine down, and check on it every 15-30 minutes afterwards. Does the system reclaim the tank contents? or does the contents stay in the tank? Should always have some.


You cna very well have a headgasket starting to go, allwoing air to be forced into the cooling system. Doesnt necessarily need to expose enough combustion gases to fail a sniffer/blue bottle


What does the radaitor cap look like? ANy super shiny bits under the cap, indicating something is being stubborn adn rubbing? any debris? does it collapse with your finger strength?
Radiator cap was replaced, but has a few black pieces of what appears to be old rubber from a failing hose on it. That hose was replaced.

I added radiator flush chemicals yesterday to see if I could knock a blockage loose (I will remove these and replace with new coolant asap) and the reservoir seems to be rising and falling as normal now (it wasn’t doing this yesterday). I’m going to keep monitoring it. This heat wave isn’t helping either...
 

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heat waves suck, but they do help assist in finding issues I guess.

Have you temporarily removed the thermostat? If it solves all your issues, then maybe its an old thermostat clogged up with shit.
Im not a big fan of radiator flushing unless the coolant itself is looking merky or shitty.


Sometimes a simple drain and refill with water, and running a few cycles, is enough to loosen and unload some garbage
 

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If it ends up being filled with garbage, you could go to a local junkyard, and grab a coolant filter system from some diesel truck or equipment. Filters for them can be spendy, but sometimes they utilize a simple stainless mesh screen, and have you take it apart and clean on some interval
 
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what gasket did you use, and did you put in new head bolts?
 
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