Guys I need your help plz, I had overheating problems and it should have been solved as i replaced the radiator and most components in the cooling cycle, now the temp gauge keeps rising till the 3/4 mark and suddenly drops continuously, when i turn on the lights the temp also increases, i changed the thermostat and the heat sensor and the problem is still there. what should i check? the engine is a D16Y5 on a 1997 Civic.

 

coolant fan relay.

 

Are you losing coolant? Any noticeably coolant leaks? Have you thoroughly bled the cooling system? Is there white smoke in the exhaust?

 

This tells me that it is an electrical problem, maybe a ground wire connector that is making intermittent contact. I guess a coolant fan relay may intermittantly energize and deenergize the fan, causing the temp gauge to go up or down. To check this, pull over and pop the hood when the temp gauge is rising or dropping, The fan would be on if the temps are dropping and off when you turn your lights on, even when your gauge gets to the 5/8s - 3/4 of travel point. Obviously, the fan should stay on until temps get below, say, 210F. If they stay on, that may explain the continous dropping of temperature.

 

Guess I am losing coolant but there are no leaks and there is no white smoke from the exhaust. How shall i test the coolant fan relay?

 

Does the radiator fan run when the engine temperature rises above normal? If not, unplug the 2P connector for the radiator fan switch located on the thermostat housing and then connect both terminals of the connector with a jumper wire. The fan should now run continuously. If so, replace the switch.

Next bleed the cooling system:

1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push the dash heater lever/**** to MAX heat.

3) Follow the directions in the diagram below. Skip bleed bolt step as you don't have one.