86 1.5 overheating

The overheating was so bad two years ago, the guy put a new engine in the car.
He cooked that one and I put another engine in it's place. I just finished after dark on Friday night.
So we have a different engine, with a different Water pump and sensors.
It still over heats!
I never have seen the fan running. The fan should work with +12 V applied to the terminals. If the Fan test's good, then the Thermal sensor must not be gating the +12 to the fan motor.
Where is the Fan motor control relay? Surely they dont make the Sensor pass the whole +12 supply to the Fan Motor?

Which Sensor starts the Fan? There are two sensors in the coolant. One in the radiator, and one in the back of the block under the intake manifold. Why two sensors? Anybody know that?
I haven't tested the sensors yet. I'm thinking I can connect the Ohm Meter to the sensor and drop it in some boiling water. The Resistance should go down as the water heats up the sensor.



So c'mon back and tell me what I need to know.

screw the sensor, mine quit years ago on my 83. the one on the rad controlls the fan, pull the two wires going to it out and attach them together, the fan will go on any time the car is running.

dont you know there is a temp adjustment on the back of those engines i have a 86 crx and i thought that there was something wrong until i looked around the engines and i found it it controls the fan for what temp you want it to turn on. but replacing the engine wasnt a bad idea
The overheating was so bad two years ago, the guy put a new engine in the car.
He cooked that one and I put another engine in it's place. I just finished after dark on Friday night.
So we have a different engine, with a different Water pump and sensors.
It still over heats!
I never have seen the fan running. The fan should work with +12 V applied to the terminals. If the Fan test's good, then the Thermal sensor must not be gating the +12 to the fan motor.
Where is the Fan motor control relay? Surely they dont make the Sensor pass the whole +12 supply to the Fan Motor?

Which Sensor starts the Fan? There are two sensors in the coolant. One in the radiator, and one in the back of the block under the intake manifold. Why two sensors? Anybody know that?
I haven't tested the sensors yet. I'm thinking I can connect the Ohm Meter to the sensor and drop it in some boiling water. The Resistance should go down as the water heats up the sensor.



So c'mon back and tell me what I need to know.

I believe my friend wired my fan to be on as long as the car is running, as well. It must be something with these cars where the sensor goes bad or something.

Side question - I have an '86 that originally had a 1.3 in it. It's since had a 1.5 put in. When that motor was put in, the radiator was rodded due to overheating. Fixed it for the most part but that sucker still runs hot, even with the fan always on, during the summer (especially with the a/c on). I wonder if the radiator is just in need of replacement due to clogging or is there a possibility one of those sensors is set up for a 1.3 somewhere?

a couple years ago, when I got this little darlin, the two Honda fourms had lots of questions on the 1.5 overheating. I began to feel the Rad was just too small, or the Water pump was not adequet.
Now I dont know, but I'll keep at it till I do.
I have the other engine laying in a pile of parts. I took it down looking for the engine problem. I found nothing out of the ordinary.
Both water pumps look OK to me. The head gasket was not rotted out anywhere. The head and the block surfaces were straight. I dont think the engine was the problem.
I sure appreciate the replies. Thanks guy's.

Chris331 where is that Temp adjustment on the back of the engine? What's it look like?

I believe my friend wired my fan to be on as long as the car is running, as well. It must be something with these cars where the sensor goes bad or something.

Side question - I have an '86 that originally had a 1.3 in it. It's since had a 1.5 put in. When that motor was put in, the radiator was rodded due to overheating. Fixed it for the most part but that sucker still runs hot, even with the fan always on, during the summer (especially with the a/c on). I wonder if the radiator is just in need of replacement due to clogging or is there a possibility one of those sensors is set up for a 1.3 somewhere?
in the last 20 years my family has owned my 83 1.5l and it has only overheated in the last year so it has a lot to do with age, i would first of all check the thermostat, for me that was the bigest problem, i replaced that and now it actually runs cool