Hi guys,
On my way home today I turned on my AC (83 in NY today). About 20 minutes later I started hearing the AC compressor chip in and out. It was followed with a burning smell in the cab. The heater gauge started to rise and there was smoke coming from the engine. When I opened it up, the fan at the back of the radiator was smoking.
What should be my next step. Just replace the fan and all is good or I need to replace the thermostat and all that stuff too.
Thanks for you help

 

Hi Riculus,

The first step is to determine the cause of overheat. But I would first like to know exactly where the smoke was coming from; was it from the fan blades (white plastic), fan motor, fan shroud or the back of the radiator?

Overheating is usually caused by one or more of the following, which you may already know:

1. Low/loss of coolant.
2. Air in the coolant (not likely on 850, as the reservoir is located at the highest point of the system). 3. Thermostat stuck closed.
4. Defective water pump.
5. Ignition timing incorrect (not likely on 850, as the timing is controlled by the ECU).
6. Engine overloaded, exceeding the cooling capacity of the car (very rare, and it usually happens in very hot climate with the A/C on while you're climbing a steep upgrade/towing a trailer).
7. Loss of engine oil, which may or may not appear on the coolant gauge.

I would check the following:

1. Coolant level in the reservoir. It must be between MAX & MIN.
2. Coolant leak/seepage on the reservoir or its cap.
3. Coolant leak/seepage from the radiator, around the seam between plastic resin & aluminum parts.
4. Coolant leak from elsewhere (mainly around hose connections).
5. Check the thermostat. Drain just enough coolant to access the T-stat without causing mess (unless you don't mind a mess). Remove the T-stat and check its operation by immersing it in water, then boil water; the T-stat should open when enough temp is reached. You may need a new T-stat O-ring upon re-installation. Or, you can let the engine idle (ensure enough oil & coolant are present in the engine) and touch the upper radiator hose to see if it gets warm. Keep an eye on the temp gauge not to let it overheat.

If the smoke was coming from the fan motor, there may be a short circuit. This is generally prevented by a fuse/fusible link (the cooling fan uses the latter, IAW diagram), so double-check on the fusible linkas well. Also, there is a cooling fan relay, in front of the battery so check this item as well. If you need a wiring diagram I can post it so let me know.


JPN

 

Hey,
It was coming from the fan motor. I took it to the mechanic and he checked the fuses, they all ok.(except for the cooling fan relay, i'll check that). He turn it on but the fan did not come on and the gauge started to rise so he shut it down. I would like the wiring diagram.
Thanks for theinfo it was very informative

Riculus

 

Just change the fan motor

 

Hi Riculus,

As I am not sure what model your 850 is, I'll post all possible diagrams. Please note, that I'll delete them within the next 7 days, so be sure to save them in your PC.

I'm assuming that the smoke was caused either by short circuit, or internal problem (wear) of the motor itself. I would try applying 12V to the fan motor to see if it spins or smokes.

BTW, how is coolant level in the reservoir?


JPN

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