Rotting Prelude

Car is a 94 prelude H23A1. Thermostat has been replaced twice. CTS sensor replaced, temp sender replaced. Upper coolant hose is hot lower is cold, not warm, cold. Coolant fan does not come on on it's own, both fans will come on if AC is turned on, still overheats. Temp can be kept under control if I blast the heat, which works great plenty of heat. I have bled the coolant system with a no spill funnel and cracked the bleeder. Still overheats. No tell tale signs of head gasket failure, it does not burn coolant. It isn't leaking any coolant. If I squeeze the bottom hose fluid will come up so I don't think the radiator is blocked. Water pump maybe? At my wits end with this thing.

civic-steve-94

If your heater is working then your water pump is working. You can have a partially blocked radiator and still be able to squeeze coolant out of the top. You can either use a temperature gun or remove the fans and feel with your hand if the whole radiator is not warm then its clogged. I will provide you with the description or the cooling fan system operation.

Cooling fan operation is controlled by the fan timer module, which monitors signals from a thermo sensor, underhood temperature sensor and the A/C compressor clutch. The timer operates the cooling fan by controlling voltage applied to the fan relay control coil. Battery voltage is applied directly from the main fuse to the relay switch circuit and timer bypass circuit, and voltage is applied to the timer main circuits through the ignition switch start and run contacts. The timer module controls voltage applied to the relay control coil circuit, and the control coil circuit is completed to ground either through the thermo sensor or timing module. When current flows through the relay coil circuit, the relay contacts close and voltage is applied to the cooling fan motor.

During normal operation, voltage is applied to the relay coil by the timer module and fan operation is controlled by the thermo sensor. When coolant temperature is approximately 190°F, current flows through the relay coil circuit and voltage is applied to the fan motor. When coolant temperature is below 190°F, the thermo sensor contacts are open and the cooling fan does not operate. However, when the A/C is turned on, the timer energizes the relay coil and the cooling fan operates as long as the clutch remains energized.

When the engine is turned off, the timer module remains energized and monitors signals from the underhood temperature sensor. If underhood temperature exceeds 220°F, the timer activates the fan relay and the cooling fan is energized. The cooling fan will operate for a maximum of 15 minutes after the engine has stopped or until underhood temperature drops below 220°F.

Rotting Prelude

Thanks for the reply. This all started after I fixed an issue with my alternator. My power steering pump was leaking fluid all over the alternator and belt. On my way home one day first my headlights start to dim, stereo gets quiet, speedo and tach go to 0, headlights go out almost completely, engine loses some cylinders does not want to stay running, started smelling real bad almost smelled like diesel, engine somehow stays running after everything electrical inside the car shut off. Made it home then shut it down. I then cleaned the alternator with electronic spray cleaner, replaced the belt and fixed the PS leak and it seemed fine afterward. Any possibility I broke some electrical components related to the cooling fan system doing that?

Also the radiator is dead cold at the bottom, hot at the top. I will replace it should anyway the rad in it now is some cheap aftermarket unit that looks quite thin. I found a denso rad for it under 100 dollars new, might order that.

Rotting Prelude

Welp head gasket might be blown. On a dead cold engine the coolant immditaly rises and comes out of the radiator cap after the engine is started. No bubbles, but it flows out rather quickly.

muellersfan

Replace the radiator and then go from there.