So, this civic has been family owned, I can track its life from point of sale. Was uncles car now my sons.
The car has weird temp issue. For background I have recently changed, water pump, thermostat, radiator hoses, rad cap, fan control switch, temp sending controller, and timing belt. Belt is phased accurately, no leaks, no combustion in radiator, no diesel-ing when I turn it off, no pinging under load, no power loss when driving.
The issue turned up after a trip to Los Angeles, above parts were changed in relation to chasing repair.
Symptoms are as follows. The temp fluctuates drastically, and is situationally affected. So, I hooked my scanner up to it, and it averages 195° to 200° when warm, however the temp will drop to 174° when sitting ing at idle, even while driving the car the rad fan does not switch on, but will spin if I jump the connector. New fan controller, swapped relays, new therm, this was a problem before I swapped parts as well. A/C Fan comes on immediately, when A/C activates, and oddly this will cool the engine down marginally, however when I turn the heater on, the temp drops drastically to around 175° to 180° and stays consistent, almost as if there is a circulation issue in front of the heater/blend valve. When I swapped the pump therm and hoses, I ran slightly pressurized water through the engine, radiator, and the heater core in both directions with no apparent instructions or blockage some, I just also note, the water/coolant in the engine prior to repairs, was blue throughout, and when i flushed the system literally zero, no rust or contaminents were evident. So in short it gets hotter when at speed on freeway, but stays within operating range as per my scanner, but the gauge, and physical temp reading fluctuates drastically, and only stays at steady temp when heater fan is on using recirc. setting. I know this could lead a person to believe the head gasket is bad, however, there is no combustion in radiator, no water in the oil, rad water never boils, no smoke from pipe, and all 4 spark plugs are same medium desert tan colored and no evidence of steam washing.
If anyone can lend a savage tech brain on this and give me a clue or affirmation as to what they have experienced PLEASE, PLEASE, enlighten me so I can get this back to my son.
Thank you