Whilst I can’t actually dyno the behaviours, the pics below tell a story.

The operation of the OEM clutch is explained here -  http://neuralfibre.com/paul/4wd/tuning-and-understanding-your-toyota-viscous-fan-clutch

As the pics below show, the OEM clutch has far more coupling rings, more surface area, a better adjustable valve system, and more fluid. The aftermarket is a Daikin unit.

My bet is the OEM unit will couple much more tightly.

 
OEM – Lots of rings

 
Aftermarket – not many rings

OEM – deep reservoir, adjustable

Aftermarket – shallow reservoir, fixed valves

OEM on left – more volume

OEM on left – more volume

I frequently see wiring diagrams for Driving Lights that just don’t work in many cars.

Toyota nearly always and Nissan often use a what is known as “switched earth” wiring for their headlights. They do this so that each headlight can have it’s own 12v supply and fuse, meaning in the event of a problem, you only lose one light.

In a switched earth headlight, assuming you are using a H4 bulb with 3 pins (very common) the power is switched twice. +12V is fed through a relay or switch to the common pin, and then either one of the other pins (one for High, one for Low) is alternately connected to ground through another relay or switch. If you go looking for +12V to power your driving lights or their relay in this system, you wont find it easily.

A far easier method is to always wire the trigger for your relay ACROSS the high beam bulb circuit, instead of from +12v to ground. This means that regardless of the vehicle wiring, positive or negative switched, the driving light wiring is the same.

There are several other benefits to wiring in this manner.

a) It works with either positive of negative switched headlights

b) It avoids problems with the relay not dropping out. The high beam indicator inside the car can trickle enough power through to not let the driving lights drop out. It takes about 8-9V to trigger a 12V relay, but only about 4V to hold it in.

c) It avoids problems with the relay not dropping out due to a poor contact on the headlight connection. This common fault can setup a circuit through the other filaments and cause enough voltage to be present on the high beam filament to hold the relay open. This voltage is far less across the filament than in relation to ground.

So how do you wire it?

It’s easy really. I have gone with text, as many people have trouble with electrical diagrams.

Power CCT (Heavy wire)
Battery – Fuse – Relay (Pin 87) – Relay (Pin 30) – Driving Lights – Chassis (Ground)

Switch CCT (Light wire)
Headlight Common Pin – Switch – Relay (Pin 85) – Relay (Pin 86) – Headlight High Beam Pin

Simply tap into the headlight wires / pins with vampire taps.

Presto – I guarantee it will work.

If you don’t have H4 bulbs, even easier, simply go straight across your high beam bulb wires for the trigger.

• Connect terminals Tc and E1 of Check Connector (in engine bay) and remove the short pin (normally inserted in bottom right corner).
• Turn the ignition switch on.
• Depress the brake pedal 8 or more times within 5 secs.
• You can now read any DTCs on the ABS Warning Light, but if everything is OK, you get the Normal Code (on-off blink with 0.25 sec intervals).
• Revert Check Connector to normal.

Codes

• 11=ABS Solenoid Relay Open or Short Circuit
• 31=Right Front Wheel Speed Sensor Signal Malfunction
• 32=Left Front Wheel Speed Sensor Signal Malfunction
• 41=Low Battery Voltage or Open IG1 Circuit
• 49=Brake-light Switch Open Circuit
• 56=Accumulator Low Pressure Malfunction

Their wear rate has been a little high so far, and they are vague on the bitumen, tracking and wandering a bit. It is improving as they wear down, but s straight line tyre they are not.

Here is a pic of them working over nasty stuff, mostly at 17PSI with a 100 Series Landcruiser and gear on top.

I wanted to keep the weight down, so decided a 9500lb was smaller and lighter than a 12,000lb. If I needed more pulling power, I would use a pulley block.

After reading the SA 4WD Winch Review, and getting a good deal, I bought a 9500lb Ironman Winch for $625 w/ 3yrs warranty. They are claimed to be waterproof and come with what I needed. I would have preferred a Premier winch due to the brake not being in the drum making it more suited to synthetic rope, but it was out of my price range. I would really have preferred a hydraulic Milemarker, but that was really really out of my price range, especially when I factored in questions around power steering pump flow rates.

After using steel cable and hating it, synthetic winch rope was a requirement. I figured 100ft (28M) of 5/16" (8mm) rated at 13,700LB breaking strain would do. Less rope on the drum keeps the winch closer to it’s rated pulling force. I specifically bought their "Hybrid" line, where the first 25ft is a Technora based rope, and the rest is Amsteel Blue. The Technora is more temperature stable for use on winches with a brake inside the drum. I bought mine from www.cseoffroad.com, along with the alloy fairlead, rope protector and safety thimble. The alloy fairlead was a free bonus at the time. I also grabbed 100ft (28M) of 3/8" (10mm) Amsteel Blue winch extension rated at 19,600lb breaking strain. The separate extension allows the flexibility of simply extending the pull, connecting two different points, putting a winch block in between the two etc. You need the thicker rope size if you are going to use a winch block, as it will double the pulling force – 9500×2 = 19,000lb.

The next item was a mount. Other mounts I have seen use 6mm steel plate in various arrangements. I settled for the thickest and strongest alloy channel I could get – 8.4mm x 6.8mm tempered alloy. It doesn’t have a rated "strength" in this configuration, especially after I chopped it up to get the winch to fit. I can say that in a pull to stall test, the rope snapped before the winch stalled, and the mount, while having a slight twist, suffered no permanent deformation. The winch is in an ideal position, directly between the chassis rails, very low, and as far back as possible. The mount acts to protect the radiator from sticks etc.

The fairlead I mounted into the bullbar with 20x heavy gauge rivets. Whilst I am not that confident as to their strength, in shear the steel pins combined with the tight fit should be very strong. At a 45deg pull they will be in both tension and shear, a less desirable situation. The alloy bar mounts are particularly weak in a sideways direction, so I think I’ll be avoiding heavy angled pulls. The fairlead needed to have it’s inside edge rounded a lot, as the winch sits quite low in relation to the bar.

Finally it was just a matter of the control box hidden inside the bar, the wiring and lockout switches. I recommend the lockout switches be waterproofed underneath with silicon, and rubber caps fitted (I used rubber "feet"). Water pulls inside them and the copper contacts stop working.The winch is wired with a switch to each AGM battery, letting me use either one, or both.

By dropping the steel cable and roller fairlead, using an alloy mount, not using a 12,000lb winch and keeping the alloy bar I have kept nearly 75KG off the front of the car. Just as importantly the weight is as low and far back as possible, something most winch bars don’t do. Whilst I accept it’s not as strong as a steel winch bar, it has passed every test I can throw at it so far.

Finally – it’s a whole lot cheaper than driving into ARB, and with Mickey T MTZ’s, twin Air Lockers and some lift, hopefully I won’t need to winch too often (yeah right).

The heaviest aluminium alloy channel I could find. It is also tempered (or so the guy said). 8.4mm base, 6.8mm walls.
Trimmed to fit winch and chassis rails with lower bull-bar mounts. I should have rounded the corners more to stop fatigue.
Winch fits nice and snug.
Alloy hawse fairlead mounted in the factory bar. Yeah I know, I know. If it snaps the rivets then I’ll do something sttronger. The alloy is 6mm checker-plate. The bar is not that strong, nor are the bar mounts.
Terminating the high temp Technora fibre.
Had to grind the allen key to fit the link on the rope.
All spooled up. Rope protector is the black bit. I have a strong plastic / rubber  flap that covers this gap keeping grass and mud out.
Pic when fitted. Yes, I suspect it may snag something one day.
The lockout switches with waterproof covers. They don’t like water in them, and then don’t work.
Internals of the waterproof control box. It’s zip-tied inside the bullbar.

The stock Toyota cooling system can sometimes be somewhat marginal. The suspicion for this falls on every component and modification in the system.

• Radiator (Size / Efficiency)
• Thermostat (Brand / Effectiveness)
• Water Pump (Flow, Cavitation)
• Radiator Cap (Quality, Pressure, Leaks, Recovery)
• Coolant (Freezing / Boiling points, Specific heat, Anti-corrosion)
• Hoses (Restriction)
• Engine Type (Diesel / Turbo / Petrol)
• Engine Load / Modifications (Diving style, load on vehicle, Mods)
• Gearbox (Auto Cooling, Slipping)
• Airflow (Obstructions / Restrictions In / Out, Forced / Natural)
• Ambient Operating Environment (Temp, Altitude, Terrain)
• Shrouds (Closeness to Fan, Leaks, gaps between radiators)
• Fan (Size / Pitch / Airflow)
• Fan Clutch (Lockup Temp / Stages / % Slip)
• Temperature Gauge (Damping / Accuracy)
• Bullbars / Winches / Lights / Antenna’s / Plates / Screens

Ask anyone and they’ll start listing random items from the list above that they have seen before or are suspicious of. It would appear that the issue is simply that the system is marginal in certain areas, and several small changes may be enough to tip it over the limit.

The end goal of a cooling system is to transfer heat to the surrounding air. All the other components are only there to allow this transfer to occur in some improved fashion. There are plenty of air cooled motors in existence that do not have these complexities, and they too may be subject to overheating.

It would appear that Mr Toyota VERY closely engineers his vehicles, with many parts sharing multiple purposes, and many many tradeoffs being made. This is good engineering, but it means that small changes may have many unintended impacts. Despite this, it appears the Landcruiser and Hilux are intended to be frequently modified. There are many attachment points, and the OEM design has many dealer supported aftermarket options that are not from the Toyota factory.

If all the basic checks have been performed on the cooling system – no leaks, nothing obviously blocked, quick warm up, infrequent overheating except under specific circumstances, then it is a fair bet that the overall system is simply marginal. In this case, a dramatic increase in specific areas may yield a significant benefit.

In my case the overheating was limited to situations with a pre-turbo EGT in excess of 550C. This equated to High Load or High Speed driving. Despite expectations, off-road steep terrain (sand excluded) does not yield high EGT’s. Mountain Ranges, Large Trailers, Roof Racks, High Speed or Deep Sand all would yield high EGT’s and therefore problems.

I have measured many temperature points around the engine bay, and spent some time listening to the engagement and disengagement of the fan. All this yielded much confusion rather than understanding.

I replaced most components, some twice. It was during this that I had time to closely examine and understand the Toyota Viscous Fan Clutch. Possibly more than any other component, this is the key item in the cooling system. It is this that creates the airflow, not vehicle forward speed. Without airflow, the radiator is not effective. My experience was very similar  in a Toyota Surf I had owned previously. It is common knowledge that additional Silicon Fluid will often improve these units. What is not common knowledge is:

• Brand new OEM clutches appear to be under-filled
• They can be adjusted where they engage
• There are 4 separate engagement stages
• Testing cannot be done one the bench. The device requires centrifugal force to operate.

Credit goes to Frank for his guide on how to split and refill the fan clutch. I am just explaining the operation in further detail.

It must be remembered that these types of fluid couplings always have some slip. They may slip by 98% (free spin) or 5% (coupled), but there is always slip. It is difficult to test the slip in any simple manner, and impossible to bench test. Therefore a fan that appears to be engaging and disengaging successfully, may in fact be slipping at 50%, significantly reducing maximum airflow. Worse, the slip will be only happen at high RPM and maximum load.

The key points are that there are 4 operating stages, and that there is not enough fluid to couple the system adequately.

This is why so many people report success with simply adding more fluid. Adding fluid means that when the system is operating with the valve fully open, the rings are full of silicon fluid, and not partly full. The only drive is through the fluid, so insufficient fluid will reduce maximum coupling ability. There was clearly not enough fluid in the unit to fill all the rings to the depth of the final valve.

The factory engagement points are also quite high. This reduces noise and fuel consumption, but also means maximum engagement doesn’t occur until the air temp is around 95C. Engine coolant temperature will always be higher than air temperature.

This was all tested with a Digital Thermometer.

Temperature Set Points (all at 1/2 open)

Pictures of operation:

Fan Clutch
The 2 halves opened
The “drive disc” spins freely in the housing except for the silicon fluid.
The “drive disc” and the “front half” share these closely spaced rings. It is these rings, and the silicon fluid in the gaps between them that couple the system together.The inner ring is taller than the others. The oil is slowly thrown to the outside of the system by centrifugal force.
The fluid is rated at 10000 Cst – Centistokes – a measure of viscosity
The valve that controls where the fluid flows. It operates over 4 stages:0) Closed A) Some oil to some rings B) Some oil to all rings C) Maximum oil to all of rings This is why it seems to be more than engaged / disengaged.
The temperature sensing Bi-Metal spring on the front face that controls the valve.
The reservoir behind the valve disc in the front half where the fluid is stored. When operating it is held here by centrifugal force, and pumped here by the slipping “drive disc”
The “vanes” on the edge of the drive disc in the rear half that pump the fluid forward to the outer channel for return to the reservoir. Some slip is required to allow the pumping to occur.The slots in the back of the disc pump the fluid from behind the disc to the edges, and then to the channel at the front. The rear of the disc is not used for coupling.
The wedge shaped guides and small holes in the front half that collect the fluid from the outer channel and push it back into the reservoir.
Adding Fluid
Adjust the valve set point by loosening the 2 screws and rotating the disc. The outer valve should be 1/2 open at about 45C for Australia. (US quotes 35C). Air temp will always be less than engine water temp.
Getting the fluid level right is a little difficult and involves some guesswork.The minimum amount required is enough to fill the entire outer rim past the depth of the fins in both halves, this fully couples the unit. The maximum amount is when the reservoir in the front is full and overflows through the central hole. Not so simple though, as full is controlled by centrifugal force, so when operating it fills the “outside” of the reservoir, not the bottom. Luckily there is a fair tolerance between the two. Overfull will couple the fan all the time. Mine took 1.5 tubes of fluid in addition to the factory fill to stay a few mm below the level of the valve disc.

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It’s fairly common knowledge that the OEM Toyota temperature gauge has a large “dead spot” in the centre of it’s range. This spot is deliberately engineered to reduce the apparent fluctuations and make the car appear to run at a constant temperature unless there is a significant problem. This works fine for most, but those of us that like to know what’s going on sooner rather than later demand a little more detail. Many people fit an aftermarket gauge somewhere in the car, I figure, if the factory gauge is already there and can be made better, do that.

One of the clever guys over at ih8mud figured out the circuit and how to modify it in his 80 series. He deserves full credit for the original article and all the work behind it. There is also a version for the Toyota Surf and Hilux.

The gauge circuit in my ‘98 HZJ105R was a little different to the 80 Series, so I had to re-do the calibration to suit. I had the opportunity to see the inside of and post ‘04 update dash, and unfortunately, it’s quite different. Someone will need to do their own testing and research on that one.

I bench tested various setups and found the following as a simple description.

Bench testing w/ Digital Thermometer

Heating the sender unit in vegetable oil

Mmm, wiring.

Resistors and Diode

We do not change the 15 Ohm resistor.

There are 2 components we replace, a resistor and a diode. The diode is what makes the gauge “non-linear”. Rather than explaining what they do in a wheatstone bridge, I’ll explain their effect on the gauge.

The gauge with no input actually sits in the middle of the scale. The 75 Ohm resistor we change “sets” what temperature the middle of the scale is to be. A lower value resistor sets it higher, a higher value resistor sets the scale lower. I found the following:

• 100 Ohms = 90c
• 120Ohms = 85c
• 87 Ohms = 95c

Gauge w/ no input – centres on scale.

The small glass diode gives a non-linear (dead spot) in the needle’s range. We replace this diode with a resistor to make the gauge react “normally”. The value of this resistor determines the “range” of the gauge. A lower value resistor gives large movement for small temp changes, a high value resistor gives less movement. Using no resistor with a 90C centre means the gauge hits the red at 94.5C – a little too low.

No Damping Resistor – large deflection

I found a value of 82 Ohms gives a good range with 115C touching the Red, 125C middle of the red and 65C touching the Cold. Properly mixed coolant boils at approximately 125C – 128C at 14PSI, and I’m not interested in below 65C, as the engine is not yet at operating temp.

This combination gives me the best combination of “”operating near the middle” and “enough movement to see what’s happening”. With the above detail you can adjust your own numbers if you wish.

The 100 Ohm resistor gets hotter as engine temps increase and will possibly exceed 1 watt. I recommend a 2 watt resistor. 5 Watt is very large and may not fit or be too heavy. The temp sender resistance decreases with heat, increasing current through the resistor.
The 82 Ohm resistor dissipates less than 1/4 watt, but I used a 1/2 watt to be safe.

	Original	Modified
130
120
110
100
90
80
70
60
50

You will need the following

• OEM ‘98-‘04 Landcruiser Dash
• 2 watt, 100 Ohm resistor
• 1/2 watt, 82 Ohm resistor.

Remove the gauge pod from car and disassemble. Be careful removing it from the car – there are 4 screws and 2 bolts. The bolts are captive and hold the plug connections, but need to be unwound a lot to release the plugs.
Remove the temperature / oil pressure gauge assembly.
Remove the 75 Ohm resistor and Diode.
Replace the 75 Ohm resistor with a 100Ohm and the Diode with a 82 Ohm.

Detailed pics below (5C steps)

	Original	Modified
130
125
120
115
110
105
100
95
90
85
80
75
70
65
60
55
50