R32 Gtr Engine Fan Temperatures

[Bozz]

I'm finding in stop-start traffic, even when its 20 degrees outside, the engine fan engages and makes the car sound like an EA Falcon.

Around 22-23 degrees, the fan is always on.

No overheating at all even yesterday with the car saying outside temp was 42 degrees, in stop start traffic, with the air con on. Just noisy fan.

When do others find their fans coming on? I'm wondering if I have an airflow issue between the FMIC and radiator. Should there be a tray between the base of the front bar to help the radiator get air?

Cheers

[blind_elk]

The fan is driven by the engine, so it's always "on". If it's just noisy, then maybe the viscous clutch is stuffed.

[mad082]

if it is noisey then it means the viscous clutch is fully engaged and drawing maximum air. as for outside air temp, that plays only a small roll as to how much it comes on full. if you drive it hard on a 10 degree day it will come on, or if you baby it along on a 30 degree day it might not.

also don't just rely on the stock gauge in the dash to know when your car is getting too hot. they are a 2 stage gauge. basically they don't show that the temps are rising until the temps are already extremely hot.

in start stop traffic it is common for the fan to kick in fully because of the lack of airflow through the radiator compared to when you are constantly moving. however if it is happening on cool days it may be a sign that the thermostat or water pump aren't working 100%. but you would really need to see what the temps are doing with a proper temp gauge as it may still be fine and there may be no problem at all.

[Bozz]

if it is noisey then it means the viscous clutch is fully engaged and drawing maximum air. as for outside air temp, that plays only a small roll as to how much it comes on full. if you drive it hard on a 10 degree day it will come on, or if you baby it along on a 30 degree day it might not.

also don't just rely on the stock gauge in the dash to know when your car is getting too hot. they are a 2 stage gauge. basically they don't show that the temps are rising until the temps are already extremely hot.

in start stop traffic it is common for the fan to kick in fully because of the lack of airflow through the radiator compared to when you are constantly moving. however if it is happening on cool days it may be a sign that the thermostat or water pump aren't working 100%. but you would really need to see what the temps are doing with a proper temp gauge as it may still be fine and there may be no problem at all.

Thanks for that,

I should have been explained better in my original post.

I've just rebuild the engine and I put a new water pump on, along with a new radiator.

My old RB20DET R32 would only engage the viscous fan clutch in 30+ degree days, with the air con on and while travelling slowly or stop-start. On a 25 degree day, it would always be disengaged/free spinning.

The GTR engages the fan clutch on an 18-20 degree day, without air con in stop-start driving. My understanding is it could be:

1) Faulty viscous clutch, engaging too early

2) Poor airflow. Perhaps after going through the intercooler, some air passes under the car instead of going through the radiator. I have the stone tray in there to push hot air far away from the radiator intake but wonder if I should extend the tray from the radiator to the front bar, enhancing how much cool air gets into the radiator.

3) By design - all GTR's do it.

That's why I posted the thread, to find out in various situations, when the viscous fan engages on other people's R32 GTR's, to figure out if I should fix something thats broken or if it's meant to be like that.

Thanks

[blind_elk]

Someone (might be me) is not understanding what is going on here and just what the problem appears to be.

The ambient temperature has nothing to do with the operation of the viscous clutch fan attached to the water pump.

The viscous fan clutch is always "engaged", because it is attached to the water pump which is driven by a belt driven by the engine's crankshaft. The speed of the fan varies with engine speed. As the engine spins faster, the liquid inside the clutch thins (reduces in viscosity), reducing the drag on the clutch, so the fan blades don't spin as fast (resistance of the blades through the air slows the blades). When the engine slows down, such as in stop-start traffic, the fluid thickens to cause the fan blades to spin at approximately the same speed as the engine and draw air through the radiator.

If the engine still operates within temperature parameters, what does it matter how, when, where, or why the fan "engages"?

[Bozz]

Someone (might be me) is not understanding what is going on here and just what the problem appears to be.

The ambient temperature has nothing to do with the operation of the viscous clutch fan attached to the water pump.

Consider the water pump pulley the 'input shaft' and the fan blade assembly the 'output shaft'. I refer to the fans operation as 'disengaged' when its freespinning and delivering less than 1:1 input to output rotational speed through the silicone fluid. I'm fully aware it still has a small amount of torque applied to it. It is 'engaged' or 'on' when the bimetallic strip in the VC deforms a certain amount, locking the input to the output, delivering exactly 1:1 input to output shaft speed. Think of its principles being similar to a torque converter with a lockup clutch.

The ambient temperature plays a very important role in the operation of the VC. When the fan is disengaged, lets assume it pulls (hypothetically) 300-600cfm of air at idle and up to 5,000rpm, due to the VC design.

Lets also assume that when the VC is locked, the fan pulls 1,000cfm at idle and 5,000cfm at 5,000rpm (I know there are many other factors in the dynamics of airflow and non linearities in the examples I use below, I'm ignoring them for the purpose of the example)

Put a beer in the fridge and put another one in the freezer. Which one cools down quicker and why? To remove a given amount of heat from the coolant, an amount of air must pass over the radiator's fins. If the air entering the radiator is cooler, less air is required through the radiator to remove a given amount of heat. If the air temp entering the radiator is warmer, more air is required through the radiator to remove the same amount of heat.

If the coolant in the radiator is 80 degrees and the air entering is 10 degrees, very little air is needed to drop the temperature of the coolant. The coolant coming out of the radiator will be pretty much at ambient temperature because the thermostat is barely cracked open, causing the coolant to flow through the radiator very slowly.

If the coolant in the radiator is 80 degrees and the air entering is 40 degrees, a LOT more air is needed to drop the temperature of the coolant. The coolant coming out of the radiator may be well above ambient temperature because the thermostat is significantly more open, causing coolant to flow through the radiator far more rapidly. If the air going through the radiator is constant, temperature differential between the ambient air and coolant exiting the radiator will be significantly higher than the previous example.

At low ambient temperatures (lets say 10 degrees) and mild driving with the VC disengaged, the fan pulls more air than needed through the radiator. The air through the top few CM of the radiator may be 80 degrees however by the time it's reached about half way down the radiator, it might be down to 20 degrees. Remember the thermostat will reduce the water flow through the radiator so very little air is needed to cool the slow flowing coolant. Therefore, the average air temp passing the VC may be only 30 degrees.

At high ambient temperatures, the water may be 80 degrees at the top, however only cooled to 75 degrees by half way, and down to 72-ish degrees at the base of the radiator due to the thermostat being wide open and a large amount of coolant flow. So the average air temp passing the VC is approximately 75 degrees.

Therefore the VC will lock when the air passing over the VC's fins exceeds a given temperature. If the VC were to always remain locked, fuel economy and performance suffers due to the engine having to drive the fan at high speed. The purpose of the bimetallic strip in the VC assembly is to lock the input to the output, providing large amounts of air through the radiator.

So on a 40 degree day, you expect the VC to be engaged but I did not expect it to be engaged on a 20 degree day.

The viscous fan clutch is always "engaged", because it is attached to the water pump which is driven by a belt driven by the engine's crankshaft. The speed of the fan varies with engine speed. As the engine spins faster, the liquid inside the clutch thins (reduces in viscosity), reducing the drag on the clutch, so the fan blades don't spin as fast (resistance of the blades through the air slows the blades). When the engine slows down, such as in stop-start traffic, the fluid thickens to cause the fan blades to spin at approximately the same speed as the engine and draw air through the radiator.

If the engine still operates within temperature parameters, what does it matter how, when, where, or why the fan "engages"?

I'm asking R32 GTR owners to share at what approximate outdoor temp the VC in their cars engages. I want to know if I need to fix a problem or if it's by design. If it's by design, I will modify it to improve cooling and reduce the amount of time the VC remains locked.

So in stop-start driving, without use of AC, what temp do owners of R32 GTRs notice the VC come on?

Thanks

Edited December 19, 2009 by Bozz

[Godzilla32]

The heat soak from the engine will lock up the viscous hub and fully engage the fan. I thought it had a bi-metallic strip on it which engaged it? The winding on the front of the hub?

[Bozz]

The heat soak from the engine will lock up the viscous hub and fully engage the fan. I thought it had a bi-metallic strip on it which engaged it? The winding on the front of the hub?

Yep, thats exactly what locks the VC

When babying it around, especially in heavy traffic, what outside temperatures do you notice it engages?

Cheers

[itease]

My 32 GTR is doing the exact same thing as yours. It never used to do it but ive noticed within about 5-10 mins of driving easy it engages and will stay on.

It could be that the fan itself it stuffed. im yet to check mine out. but i was thinking i could replace it with thermos and free up abit of room as well.

[Godzilla32]

They are known to go both ways. IE: lock up all the time or wont lock up at all. I havent driven my GTR for over 4 years so i can;t tell you exactly when it comes on but i do remember it would come on from the heat soak if it was sitting for a while after it had been driven.

Deren

[Bozz]

I've solved it.

This morning I did some measurements, ambient temp was 15 degrees, clutch fan came on when the water temp in the return hose rose to 23 degrees. This obviously isn't right so I removed the fan (after removing the radiator and shroud) and started mucking around with it on a bench with a drill and butane torch. Once the bimetallic strip got barely warm (maybe 25-30 degrees), the fan locked on until I cooled the bimetallic strip with some freeze spray.

I dont recommend anyone try this unless you really know what you're doing and understand the damage that can result from an overheated cooling system if you get it wrong.

I'll get some photos later on, I'm now waiting for the car to cool so I can put the shroud back in.

If you put the outside tab of the bimetallic strip at 9'oclock, when the centre valve is facing north-south (12 o'clock from now on), as the bimetallic strip warms, it turns the valve anticlockwise, towards 11 o'clock. This engages the viscous clutch. The solution was to bend the bimetallic strip a poofteenth of a bees dick to have the valve resting two tenths of bugger all further clockwise. It really is *that* touchy - with my experimenting today, I went too far on and off many times resulting in a fan that would never turn on or never turn off.

Eventually I worked out what I was doing wrong - after bending the bimetallic strip, when I reinserted the tab at the 9 o'clock position, I was putting an axial load on the centre valve preventing it from spinning freely due to the way I bent the strip. After I figured out what I was doing wrong, a few more fine tuning sessions and I think its right - fan comes on when return temp of water is approx 45 degrees and goes off when it falls to about 30 degrees.

Cheers

[Bozz]

Damnit, its shit itself again. I reckon the viscus core is doing wierd crap because the engage/disengage points of the bimetallic strip remain in the same spot I left it so it hasn't bent.

Can anyone share what outside temperature their engine fan clutch engages in regular day to day driving?

[mad082]

forget outside air temp. don't even bother posting about it again. get yourself a water temp gauge and see what it is doing. i've seen cars boil on cool days before, so outside temp has very little to do with what your engine temp is doing if you have a failing cooling system, and that seems to be what you are ignoring. i once had an issue with the cluth fan on my 33 screaming on mid 30 degree days. even at night when the temp would drop down to mid to high 20's it would still be roaring. i put a temp gauge in and discovered that it was running at around 95 to 97 degrees and that was the cause of the fan going. then it was just a case of finding the cause of the high temp, which seemed to be the water pump.

and everyones fan is going to kick in at different temps due to different cars cooling systems working at different effeciencies due to things like thermostat age, radiator condition, frant bar design, and then other things like driving style

[Bozz]

I've no interest in discussing this with you, mad082.

I'm after specific information from people who have an R32 GTR.

Cheers

[mad082]

i don't care if you aren't prepared to discuss it with someone without a r32 gtr. as i said, EVERYONES FAN WILL COME ON AT DIFFERENT AMBIENT TEMPS BECAUSE IT IS CONTROLLED BY THE TEMP OF THE COOLANT, NOT BY OUTSIDE AIR!!!!!!!!!!!!!!!!!!!!!!

stop being so stupid and get a bloody water temp sensor.

ah screw it, people have tried to help you out but you don't listen. i hope your overheating issue gets worse and you end up blowing your engine.

[Bozz]

Anyone?

[NSNPWR]

i don't care if you aren't prepared to discuss it with someone without a r32 gtr. as i said, EVERYONES FAN WILL COME ON AT DIFFERENT AMBIENT TEMPS BECAUSE IT IS CONTROLLED BY THE TEMP OF THE COOLANT, NOT BY OUTSIDE AIR!!!!!!!!!!!!!!!!!!!!!!

stop being so stupid and get a bloody water temp sensor.

ah screw it, people have tried to help you out but you don't listen. i hope your overheating issue gets worse and you end up blowing your engine.

Sorry but youre wrong, the factory clutch fan is not controlled by coolant temps, how can it be? Its not electric nor does it have coolant flowing through it...its triggered by Air Temp, Air Temp under the bonnet...so if anything he should be measuring air temps in the bay around the fan area...

Im having the same problem as the OP and I have a 32 GTR...the fan always seems to be on, its loud as an EA Falcon Taxi...

Tonight I drove it with no clutch fan at all and im sure as hell it felt less held back and no noise...I just had the Air con fan running for SOME airflow...car didnt go over 82c, im going to look at mounting a 16" 3000cfm fan in the factory shroud me thinks...

Edited February 19, 2010 by NSNPWR

[mad082]

Sorry but youre wrong, the factory clutch fan is not controlled by coolant temps, how can it be? Its not electric nor does it have coolant flowing through it...its triggered by Air Temp, Air Temp under the bonnet...so if anything he should be measuring air temps in the bay around the fan area...

Im having the same problem as the OP and I have a 32 GTR...the fan always seems to be on, its loud as an EA Falcon Taxi...

Tonight I drove it with no clutch fan at all and im sure as hell it felt less held back and no noise...I just had the Air con fan running for SOME airflow...car didnt go over 82c, im going to look at mounting a 16" 3000cfm fan in the factory shroud me thinks...

and tell me, what is the main contributing factor of air temps in the engine bay? the coolant temp. if the coolant temp is sky high, even on a cool day the engine bay temps are going to he higher since a majority of the air coming into the engine bay is being drawn through the radiator. also since the fan attatches onto the front of the water pump, which is going to absorb heat from the coolant and thus the viscous coupling is also going to absorb some of the heat from the water pump, once again the coolant temp is indirectly affecting the workings off the fan. also any heat radiating off the engine will also be directly related to the coolant temp. the lower the coolant temp the lower the temp of the engine block and the lower the temp of the air in the engine bay.

unlike you the OP doesn't appear to have actually checked (or at least hasn't posted up about it) to see what his water temps are when his fan is roaring. in your case, your viscous coupling is obviously stuff and staying locked up, but in the case of the OP, his car may possibly have a cooling system issue that is cause the car to nearly boil, but he isn't bothering to look into that, he just wants people to post up the ambient temp that their fans are coming in at, which is a pointless exercise as every car will be different as not everyone's cooling system will be work at the same effeciency as others. if someones radiator is 15% blocked then their fan will kick in at a lower them than someone with a brand new radiator. so the OP should be looking at what temp his engine is actually running at as that will immediately tell him whether his fan is working properly or not and he could've had his problem solved 2 months ago.

[Bozz]

Sorry but youre wrong, the factory clutch fan is not controlled by coolant temps, how can it be? Its not electric nor does it have coolant flowing through it...its triggered by Air Temp, Air Temp under the bonnet...so if anything he should be measuring air temps in the bay around the fan area...

Im having the same problem as the OP and I have a 32 GTR...the fan always seems to be on, its loud as an EA Falcon Taxi...

Tonight I drove it with no clutch fan at all and im sure as hell it felt less held back and no noise...I just had the Air con fan running for SOME airflow...car didnt go over 82c, im going to look at mounting a 16" 3000cfm fan in the factory shroud me thinks...

When I get time, I'm going to measure up the EF/EL thermofan. If they fit I'll post results.

I found the last comment particularly amusing - that a stuck viscous fan could somehow result in an overheated or blown engine

I also find amusing the suggestion a blocked radiator could cause the fan to come on early. Also the ignored comments where I wrote a new water pump and radiator are in my GTR, as well as the ignored comments about how radiators and heat transfer actually works in the real world.

Its clearly a fan issue on my car, quite possibly the same as yours.

Edited February 20, 2010 by Bozz

[Bozz]

unlike you the OP doesn't appear to have actually checked (or at least hasn't posted up about it) to see what his water temps are when his fan is roaring

fan comes on when return temp of water is approx 45 degrees and goes off when it falls to about 30 degrees.

oops

Edited February 20, 2010 by Bozz