Thread

I have a 1991 DX hatch with the auto trans (commuter car) and I'm trying to troubleshoot the cooling system.

The radiator fan will not come on at all when the coolant is hot.

However, the fan will come on when I turn on the A/C so I'm thinking that it's not the fan relay or motor. Since according to the wiring diagram the A/C goes through the same relay.

As a result, I'm looking at it being a sensor problem. Here's where it gets confusing. There's a sensor on the passenger side of the engine under the distributor. According to the wiring diagram that sensor plugs into the ECU but, seems to have nothing to do with running the fan.

There is a temperature SWITCH on the rear of the block. This one plugs into the relay. But, it also runs the coolant temp gauge in the instrument panel according to the wiring diagram. My temperature gauge works though. Is it possible for the switch to fail but still give a temperature reading to the gauge? Furthermore, I can't find anywhere a part number for this thing let alone where to get it from. I even tried Majestic's site but, nothing is listed for sensors.

I've also read that the ignition timing uses information from the coolant sensors to adjust timing. I think I may have a issue here as between 2k and 2.5k rpm's the car is a dog. So perhaps the sensor on the side of the engine that goes into the ECU is bad too. This looks like just your average coolant temperature sensor and seems to be easy to find.

And finally, I seem to have a coolant leak. When the car is parked after driving it, a small amount of coolant seems to be coming from behind the crankshaft pulley. I'm pretty sure it's coolant since the spot will go away in the sun. Oil does not evaporate but, water does, which is why I think it's coolant.

I've not had a chance yet to do the usual visual checks but, is there something that's common/known to cause a leak in this area that I should focus on?

Any help/advice you can give is appreciated.