Well I’ve finally found the time to sit down and do the two finger typing thing, at work. My PC at home spat a dummy (30GB IBM DeskStar HDD down the drain with all the data onboard, bugger!!!). I’m currently installing a new 200GB HDD, a new BIOS on the motherboard (to run such a large HDD), Windows XP Prof., a whole bunch of new drivers to run on XP, Windows Office 2003 and everything else to boot. I guess I should have expected it, I bought it in May 2001 so it a dinosaur, what do I do, upgrade or salary sacrifice on a new laptop?
KK, Rossco, Rammy and others, here’s my attempt to “eliminate the ghosts”. Although this has more to do with another topic, it is closely related to the deliberations of why an oil cooler should or should not be fitted; perhaps I’ll post it in the ‘other post’ at a latter date. In simple terms I’ll now try to explain how I believe the Eliminator cooling system was designed and, in my experience, how it works (assuming everything is serviceable).
1. Ignition OFF – Fan runs anytime temp is above 97°C @ radiator base.
2. Ignition ON and oil is below 120°C – Fan ON anytime temp is above 97°C @ radiator base.
3. Ignition ON and oil is above 120°C – Fan OFF if temp is below 110°C @ thermostat inlet.
4. Ignition ON and oil is above 120°C – Fan ON anytime temp is above 110°C @ thermostat inlet.
Now I’ll try to explain in a more detailed manner. I apologise to those without access to a Kawasaki ZL900/ZL1000 Motorcycle Service Manual Supplement manual/wiring diagram. For those of you with a manual/wiring diagram, I’ll refer you to the item location/numbers in the figure on page 3-2 and the wiring diagram items (bracketed numbers) on page 16-13 for the ZL900 and 18-30 for the ZL1000 as follows:
Item layout/location on page 3-2:
1. – 97°C (207°F) Fan Switch - Base of Radiator
3. – Fan Switch Relay
4. – Fan relay
5. – 120°C (248°F) Water Temperature Switch - Thermostat, discharge side
7. – 110°C (230°F) Fan Switch - Thermostat, inlet side
Cooling Fan System Wiring on page 16-13 & 18-30
(
– 97°C (207°F) Fan Switch
(3) – Fan Switch Relay
(2) – Fan relay
(9) – 110°C (230°F) Fan Switch
(10) – Engine Oil Temperature Switch (120°C?) – located in the engine sump
The (°F) figures are for those more familiar with Fahrenheit, but here I’ll use Celsius (°C) because that’s what KHI uses in the manuals. The term ‘switch’ refers to what many would call a sensor but technically they are purely a simple switch (to ground).
The Engine Oil Temperature Switch fitted to my bike is 110°C, I can’t find it in the ZL supplement but the ZX900 base manual lists it as 120°C on page 16-31. For ease of clarity against the other water temp switches (97°C/110°C), I’ll refer to it as a 120°C Engine Oil Temperature Switch, though not to be confused with item 5, 120°C Water Temperature (indication) Switch.
Firstly let’s get item 5 out of the way. This 120°C Water Temperature Switch at the discharge side of the thermostat is purely for cooling system over temperature indication (dual function water temp/oil pressure light in the tacho) and has nothing to do with controlling the cooling fan (see Water Temperature Warning System on pages 16-16 and 18-32).
Now the Cooling Fan System; first cab off the rank, lets explain why the fan often runs even when the key’s turned off. At rest, with ignition off, there is always power available at the Fan Relay (2), control and contact, hot off the battery. The power to this relay’s control is grounded via the Fan Switch Relay (3) contact which, at rest, is grounded through the 97°C Fan Switch (
. So to close the contact of the Fan Relay (2) and operate the fan all that is needed is for the water temp to rise above 97°C. Why such a low temp of 97°C I hear you ask? The reason the system has been designed to run this way with the ignition off has more to do with thermal expansion than trying to keep the system temp below 97°C. It’s well known that when an engine is initially turned off (i.e. the water pump is not running) there is a considerable amount of heat soak from the hot engine into the cooling system owing to the fact that there is no water flowing through the radiator and nor is there any airflow through the radiator. This causes the water temperature (read ‘volume’) to rise significantly and if not managed by reducing the temp quickly can cause the cooling system reservoir to overflow. Although not much can be done to reduce the water temp in the engine, reducing the temp of the water in the radiator alone is enough to reduce the total system temp/volume and thus resolves the overflow problem. The reason the 97°C Fan Switch (
is located at the base of the radiator is because this is the coolest position in the system and where the radiator water will first flow after being cooled by the fan running off the battery (wouldn’t want to return to a dead horse on a hot day). This is why some may assume gremlins are in the system as they walk away from the bike and the fan suddenly starts to run, particularly if the water was just below 97°C when the engine stops.
This system would also suffice with the ignition ON however 97°C is too cool and not the optimal temperature to be maintained in an efficient internal combustion engine. This is why the 110°C Fan Switch (9) was introduced (at the inlet side of the thermostat, virtually the hottest part of the system). Firstly, when the ignition is on, power is available to the control side of the Fan Switch Relay (3) which is grounded via the 120°C Engine Oil Temperature Switch (10). Secondly, when the engine oil temperature reaches 120°C the Fan Switch Relay (3) is energised and the contact is moved from the 97°C Fan Switch (
to the 110°C Fan Switch (9). So in other words when the engine oil is maintained above 120°C the fan is maintaining 110°C in the cooling system. The by-product of this system is that before the engine oil reaches 120°C, the fan is controlled by the 97°C Fan Switch (
.
Let’s assume that for every psi increase in system pressure the boiling point of water also increases 3°F. Therefore water in a pressurised system of 11-15psi (ZX900 spec, I believe ZL spec also) would boil between 118°C and 125°C (245°F and 257°F) dependant on the spec and condition of your radiator cap. The boiling point of specialised radiator fluid is different again and much likely to be higher. It therefore appears to be quite reasonable that KHI would chose 110°C and 120°C for the cooling system ‘normal temp’ and ‘over temp warning’ respectively. So it would appear that this system has some method in its madness. I for one would not recommend changing the sensor specs, too low and you risk premature wear in the engine, too high and you risk boiling the system. My entire system is as per spec (except for perhaps the oil temp switch) and I’ve never had overheating or overflow problems, even after a 6.5hr ride in 44°C (111°F) summer heat.
Without comprehensive understanding of this system it would be very easy to assume there’s a problem with a perfectly serviceable system. Remember it’s not all about the water temperature; oil temperature is also a large part of the puzzle. It is unfortunate that we can’t post pics of the diagrams on the site at the moment; it’s difficult to make sense of these things without a wiring diagram in front of you. If any of you would like a copy of the diagram, send me a PM with your e-mail address and I’ll pass it on, when I can.
I stand to be corrected on any of the details above but I do believe this to be as close as the politics is to evil. When my PC is fixed I must put together a website for such things.
