viscous coupling

[sebking]

Just to confirm.

There's a viscous coupling on the fan of my stage 1. When the engine has been running for a while the fan should spin faster because the fluid gets harder - yes?

If I try turning the fan by hand after a run fan should be more difficult to turn than when cold - yes?

I'm running hotter than I should be and I'm wondering if this is a contributing factor - eg the coupling is not doing what it should (eg not yes to my two questions)

Seb

[disco2hse]

First off, what makes you think you are running hotter than you should be?

Depending upon which thermostat you have the running temp should be 82C or 86C (IIRC, someone correct me if my numbers are wrong).

I have heard conflicting reports about the viscous fan. Some say they usually offer no problems, others that they only last 5 years max, mine is possibly as old as 24 years... So if you think you are running hot, there are other things you should check first:
The spark advance
Coolant circulation
Fuel/air mix
Blocked radiator fins
Clogged heater fins
Water pump not pumping
Oil pump not pumping
Oil radiator fins blocked
Needing an oil change, old oil has broken down or there's not enough left
Oil filter blocked/clogged
Cylinder pressure (blown head gasket)
Water pressure cap not working
...

I have also heard from others that changing fans, etc. will not make a lot of difference in the end. Remember these things can still run in very hot conditions without modification.

In answer to the question how they work, Google gave me this:
http://www.landyzone.co.uk/lz/f8/viscous-fan-57370.html

It especially talks about how to tell if it is your fan that is causing the overheating.

HIH

[sebking]

Put an after market gauge and sender in while changing the oil pressure one, made a nice pair. Any way for now the temp seems less scary too cold if anything! So what should the normal running temp be?

[disco2hse]

Hi Seb,

The temperature is dependent upon which thermostat you put in. And variations will occur if you are using lower or higher octane petrol or LPG, whether the spark is retarded or advanced. A person may choose, for example, to run slightly hotter.

However, the thermostats come in two 'sizes' 82 and 88 degrees (I was wrong previously). You can get others if you are running in hot or cold climates. I have heard that some people will change their thermostat between summer and winter, I don't. Mine is 82 degrees.

There is some variation of course. The thermostat will open and close slightly above and below the temperature indicated on it. Testing its range is easy. Just take it out and suspend it and a thermometer in a pot of water (I use one of those that you'd stick into a roast in the oven, normal thermometers will not cope with anything above about 60 degrees normally). Put the heat on and read the temperature of the water when it opens. Let the water cool down and read that temperature.

That will give some idea of the running temperature.

But if you really want to be paranoid :p put sensors in the transfer box and gearbox too.