Four Blade Fan

[Colin Morgan]

Planned to fit a four blade fan today.  However, found that whilst a two blade fan will twist and slip off, a four blade one - being more like a saucer than a stick - will not fit on without the radiator being shifted.  So it will have to wait until I have a bit more time.  

The plan is to see what the water temperature settles at with four blades - currently running in the mid-90s with the original two blade fan.

Colin

[Colin Morgan]

Have now fitted a four blade fan on my otherwise standard Ruby - same diameter and blade shape as the original two blade. On a previous run with a two blade fan and no deflectors or baffles fitted to the radiator (side or bottom) the thermocouple in the top tank of the radiator gave a steady peak temperature of 95 degrees at 40 mph. Today, with the ambient temperature again at 21 degrees and with a similar light breeze, at 40 mph the temperature did not settle but fluctuated on the digital thermocouple readout between 92 and 94 degrees, occasionally straying to 90 or 95 degrees. On return and turning off the engine this settled at 93 degrees. So the conclusion from this run is that the four blade fan lowered the peak average water temperature by 2 degrees - not as much as I was expecting. However, it is perhaps more effective at slow speeds and when stopped in traffic?

Colin

[Mark McKibbin]

I think it can be safely said that the fan is not your problem. That temp at 21 degrees would have to be something like a blocked radiator or blown head gasket. I would think your temp should be more like 70 degrees such a mild day.

[Colin Morgan]

It's the radiator that is past its prime - the idea was to see what effect the extra cooling from the fan would have. As I run the car all year round, I am happy so long as it does not boil or give other problems, such as vapour lock, in the summer. (21 is a warm day in the north of England.)

Colin

(Update: At the end of August, the radiator was swapped for a used spare that came off another car some years ago. This gives a maximum running temperature of 80 C [with 17 degrees ambiant temperature], which is more comfortable. This is with the four blade fan fitted.)

[Duncan Grimmond]

I found the swap straightforward, though there is plenty of space, perhaps too much. The engine runs cooler to the touch, I don't have a thermometer but I'm happy with the performance of the new fan.
As its called a sports fan, I'm sure I go faster now!

[Colin Morgan]

My engine seemed quieter and smoother - I think this latest fan is better balanced. Car not noticeably faster though...

Colin

[Robert Leigh]

Talking of balance I fitted a four blade fan many years ago without considering balance. It turned out to be badly balanced and the fan spindle broke at 60 mph on the M3 going to Beaulieu. Also it was a 3 blade fan after that and I had a leaking radiator! The lesson is do check and correct the balance before fitting; the supplier may not have done.
Robert Leigh

[Hedd_Jones]

the extra two blades should be eating some of your horsepower, not giving you some

[Colin Morgan]

The 20yr old fan belt is currently managing to supply the additional power needed for the new fan, but I have a spare belt ready if needed. I wonder if you get any of the power back with the 4-blade fan being a more effective propellor??

Colin

[Mark McKibbin]

Surely the extra blades would be sucking the car along so no wasted power