temp questions

[willmoodom]

couple weeks ago, i posted about a overheating situation that concerned me. with the laptop hooked up, i saw a max temp of 202f. i know i may have a small bubble in the cooling system. im trying to work that out due to the heater not getting as hot as it should. last night in 90 degree heat, and after a few wot runs, i cut the heat on at 85, i felt a little heat but at that instance, i should have been burning up. just the opposite. i was hotter just sitting in the car with the windows open. Back to my overheating issue, i went promptly and purchased a new fan clutch and the fan itself is practically brand new, removed from a 95 Q45 i found in the junk some months back. main reason for swapping out the clutch is because i didn't hear the fan engage during those hot temps. some other details are fresh coolant topped off, 180 tstat, and a better than good 95 water pump. now it is possible that what im seeing on the laptop is infact wrong due to a bad coolant sensor. so my questions are these:
at what temp will the fan engage 50% and 100%?
any reason why the fan wont engage when its supposed to ( i cant see none considering what Ive done, i mean it is belt driven)
wheres an easy spot to tap into the condenser fan to check if operational?

keep in mind that during this high heat issue, my stock gauge sits at half just above the little water wave. hasn't gotten above that.
last night after installing the new clutch i took it for a test ride though without my laptop. once my gauged showed the half just above the water wave, i could hear the whirl of the clutch fan just barely audible. as i continued the drive, i noticed it didn't get ant louder at anytime, though at a stop it was so quiet like it was disengaged. today is another scorcher and this time i will take my laptop for a few around the block runs. due to my inhibitor switch not operating correctly, im not really enjoying the ride. But im looking into that repair as we speak.

[Infinitiguy19]

See the 1997-2001 Q45 service manual on cooling system air bleeding instructions (Real simple).

A good fan clutch should not stop against a rolled up newspaper (Hopefully read) at idle. And when the engine is not running the fan should have a lot of resistance when spun by hand.

180 Thermostat? That's not OEM and every degree (Fahrenheit (F)) counts with the small cooling system (~10 quarts) of the Q45.

Cooling sensors do get corroded overtime thus becoming less sensitive (Inaccurate).

The fan clutch has oil in it much like the viscous clutch on the rear differential of the Q45. So the thicker the oil gets because of the hot engine the more it keeps the fan locked at the same RPM the engine is run at. So when the engine is cold the clutch is unlocked and the fan basically free wheels.

The electric fan is triggered by a thermoswitch on the output side of the radiator (bad design?). When the themoswitch reaches 189-199*F the thermoswitch helps complete the electrical circuit and the electrical fan in front of the condenser is turned on till out radiator output temperatures decrease to 176-187*F. And the fan on the 1990-1992 Q45's has only one setting which is high. Where as the 1993-1996* have two settings but the low setting only helps move air when the vehicle is not stationary.

You can do what I did and short to ground the thermoswitch (female connector) and have the fan come on only when the ignition switch is on or the the engine is running.

The interior temperature gauge is very insensitive in order to prevent the driver from feeling alarmed as the engine over heats (Bad design). But when the ECU sees is very accurate assuming the sensor is clean (Good coolant system maintenance).

(1994-1996 condenser fans are controlled by ECU and a better coolant temperature sensor.)

[willmoodom]

See the 1997-2001 Q45 service manual on cooling system air bleeding instructions (Real simple).

A good fan clutch should not stop against a rolled up newspaper (Hopefully read) at idle. And when the engine is not running the fan should have a lot of resistance when spun by hand.

180 Thermostat? That's not OEM and every degree (Fahrenheit (F)) counts with the small cooling system (~10 quarts) of the Q45.

Cooling sensors do get corroded overtime thus becoming less sensitive (Inaccurate).

The fan clutch has oil in it much like the viscous clutch on the rear differential of the Q45. So the thicker the oil gets because of the hot engine the more it keeps the fan locked at the same RPM the engine is run at. So when the engine is cold the clutch is unlocked and the fan basically free wheels.

The electric fan is triggered by a thermoswitch on the output side of the radiator (bad design?). When the themoswitch reaches 189-199*F the thermoswitch helps complete the electrical circuit and the electrical fan in front of the condenser is turned on till out radiator output temperatures decrease to 176-187*F. And the fan on the 1990-1992 Q45's has only one setting which is high. Where as the 1993-1996* have two settings but the low setting only helps move air when the vehicle is not stationary.

You can do what I did and short to ground the thermoswitch (female connector) and have the fan come on only when the ignition switch is on or the the engine is running.

The interior temperature gauge is very insensitive in order to prevent the driver from feeling alarmed as the engine over heats (Bad design). But when the ECU sees is very accurate assuming the sensor is clean (Good coolant system maintenance).

(1994-1996 condenser fans are controlled by ECU and a better coolant temperature sensor.)

good info. thanks. i already understood the operation of the clutch fan. its just concerning that at 200*f, the fan is so quite. usually in a different car, you hear a loud burst of fan for a few seconds until that temp falls back to tstat range. than the clutch releases.
as for the undersized cooling system, that i didnt know. would you recommend upgrading to the 2 stage fans or going after market?
will the 94-96 coolant sensor fit 90-93? what temp does oem tstat opens? if my cooling system is getting that hot, i can only imagine the transmission fluid.

[qship96]

I can always tell when the fan clutch is locked by the sound of massive air movement from under the hood- start car with engine cold and rev the motor at idle to get used to the sound.....then after driving for awhile in hot weather,stop the car and leave motor running for 5 minutes or so while parked and rev the engine, the sound should be much louder and be a air rushing type noise.

[Infinitiguy19]

Is the fan clutch OEM? I recall Qship96 saying the clutch fan on his 1996 Q45 is very loud when engauaged.

The The OEM cooling system needs more coolant/distilled water not more fans to move the air. So a bigger radiator is a plus but if you just driving normally you should be find provided most of the cooling system behaves like new.

The 1994-1996 Q45 engages the condenser fan when the engine temperature sensor (same sensor that feeds the ECU and the interior gauge.) reaches the specified temperature. I can't find the exact temperatures but I did learn the 1996 uses vehicle speed as well to determine what speed to allow the fan to turn.

The OEM thermostat starts to open at 170*F but doesn't fully open till 194*F. Do you have a external transmission cooler? If not get the biggest one you can afford and install it on the left wheel well (with electric fan pulling the air) where the active suspension cooler would be on your car. I plan to place mine their this summer.

[willmoodom]

i know the sound on start up my 4runner sounds like a jumbo jet in the morning when i first start it. my cold start hasn't been right since i bought the car. im still working on my idle. may need anew tps and it appears i need a new coolant sensor. i guess if the sensor is showing higher then normal readings, then the car thinks its warmer than it actually is on morning start up. especially these 80*f mornings we've been having for the past few months. the clutch is infiniti stock

[Infinitiguy19]

Whats wrong with the TPS? Is it set to .44 volts (OEM) or very close to it?

How do you know you need a new coolant temperature sensor? Have you done any diagnostics with a multimeter? Read the temperature of the coolant using a known good thermometer and compare the reading to the temperature sensor.