New dual temp sensor .. still no auxiliary fan..

[mgromero]

Hi guys!

I am troubleshooting an overheating issue with my car, clutch fan can shred a newspaper when the car is hot.

I noticed that the Auxiliary fan was not turning on when the needle crosses the center of the gauge, so I removed the connector on the sensor (3 prong type) and jumped the wires, The aux fan then works on high and low speeds.

I came to the conclusion that the sensor was caked, ordered a new one from Pelican, after installing the new sensor (91/99 ºC) the problem persists.

No aux fan even when the temp needle creeps to the 3/4 mark.

What can I do to troubleshoot the system? and does anyone know the temperature scale equivalent to the lines in the gauge?
Thanks guys

[SlamedIAm]

Have you verified the temperature of your coolant to rule out a faulty reading at the gauge?

[jlevie]

If the thermo switch is good and the aux fan will run at both speeds when jumpered, the fan not running when the gauge moves past the mid point could (as SlamedIAm suggests) be a problem with the gauge. But it also could be that the thermo switch isn't immersed in coolant (air in the cooling system).

If this happens when A/C isn't being used, there is a bigger problem than just the aux fan not running. The aux fan should not be necessary and is a "fan of last resort" when A/C isn't used.

[mgromero]

Thanks for both replies guys, I really appretiate this.

The temp will go to the 3/4 mark when the AC is used (both in traffic or in the freeway) or in traffic situations with starts and stops.

The thermo switch is REALLY hot to touch so I think that some water is reaching there. But you could be right, some air might be trapped there.

I dont know if the gauge isnt working, because the readings correlate with the overall situation (temp will go gradually down when running on highways, going up little by little heating on stops)

The thermostat is also brand new (80ºC)

Maybe this is a tipical airlock in the system afterall. Any further tests to be performed?

Thanks guys

[jlevie]

With the engine idling and the A/C off us an IR or contact thermometer to see what the head temperature is. It should be very close to the thermostat rating. If higher there is air in the cooling system, the thermostat is bad, or the radiator is plugged up.

[mgromero]

Thanks! I will measure the temperature with a laser thermometer.

By head you mean the actual engine block? or the thermostat housing?

Thanks again my friends

[jlevie]

Measure the temperature of the head to truly know how hot the engine is. The hottest spot is normally around the last cylinder.

[bzboardz]

what is the temp reading of the needle at the half way mark? 328ijunkie used the 82C temp switch and has it coming on right at the half way mark.

http://www.r3vlimited.com/board/showthread.php?t=210783&highlight=electric+fan+wire

[mgromero]

I didnt had the chance to measure the head with a laser thermometer yet.

Last week I changed all the coolant (put some Shellzone 75% with destiled water) and bleeded the system again. I got a hot hot air coming from the vents so the system is fully bled, no air bubbling out after a 20 minutes of running.

Ruling that out I can be sure (?) that the new sensor is fully submerged in coolant, so my question is.

if the sensor is fully submerged, and jumping the connector the fan works in both speeds then the problem is the sensor again???

[jlevie]

You really need to find out how hot the engine engine is before replacing any more parts.

[dnguyen1963]

You can buy a laser thermometer from Harbor Freight for $29.

[mgromero]

You really need to find out how hot the engine engine is before replacing any more parts.

After a month my thermometer arrived yesterday.

Today is a 30°C spring day, took the car to a trip downtown and the external temp was 39°C on heavy traffic.

After an hour in the traffic the needle went to 3/4 and went to measure some temps in the engine.

(this is not my engine but shows where the measures were made)





The dualtemp sensor is now working (tested outside) and the temperature there is rather low.

The temperature measured in both sides of the thermostat housing is normal (I assume) ... so why the needle is going to 3/4 if the car is only running 10° more than the thermostat rate?

I could not measure the "head" temperature because I need to get an elevator to do that.... the IR laser is not tiny enough to fit between all the hoses and wires.

Any input is appretiated :)

[jlevie]

Your temperature map in the picture explains why the aux fan isn't coming on and suggesst why the engine is running hot. The aux fan isn't coming on because the radiator isn't hot enough. The aux fan thermo switch activates at 91C (low) or 99C (high), but that part of the radiator is only at 70C. The thermostat housing temperature near the gauge sensor is 91C, which would be above the midpoint of the gauge. So the gauge is correct. The question then becomes why is the engine so hot and the radiator so cold. The possibilities for that are that the engine thermostat isn't opening all the way, the radiator is clogged, or the water pump isn't circulating fluid properly.

I'd attack this by replacing the radiator & thermostat and any other cooling system parts that are 10 years or more old. That could also mean replacing the expansion tank & cap, water pump, all hoses, and fan clutch.