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Four blade fan? - Howard Wright - 17-08-2024
Hi All
Since I’ve started to use my C Cab van more frequently I’ve noticed that it seems to run very hot. As mentioned in another post I decided to fit a capillary gauge to check the temperature (there was a handy boss already present in the header tank).
Well the average running temperature was around 90 degrees. Any hill or putting my foot down sent the gauge up to 100 and on a 1 in 5 near us the rad boiled. I checked the capillary gauge by comparing it with a glass alcohol gauge and it’s accurate.
The engine is one I rebuilt about 2 years ago as a spare. It was thoroughly cleaned and now has a brand new Ricardo head. Both hoses are new and the bottom one not pinched by the dynamo. Just to check I took the side branch off and it was all clean as a whistle.
The radiator is a period honeycomb one of unknown vintage so I used a can of Holts Speedflush yesterday evening. It still runs hot!
I don’t want to replace the honeycomb rad which I think is probably the problem. So I’m contemplating a four blade fan.
My question is how much more cooling do you get from a four blade over a two blade?
Cheers
Howard
RE: Four blade fan? - Ruairidh Dunford - 17-08-2024
You do get more but I am unsure as to how you would quantify the increase...
RE: Four blade fan? - Nick Salmon - 17-08-2024
It would be about two blades' worth of benefit, wouldn't it?
I'll get me coat...
RE: Four blade fan? - Steve Jones - 17-08-2024
My SWB Saloon with a very clean period type core runs a bit hot. It only ever boils the water in quite extreme conditions but it boils the petrol in the FZ float chamber at every opportunity. In contrast, my competition Ulster with a modern film core runs cool to the point that I run it without a fan belt but it still doesn't get as hot as I'd like. The Saloon does what it does whatever engine is in it (including an engine that runs cool in the Ulster) leading me to conclude that it's a radiator issue and, in addition, it can't cope with modern petrol. The modern core in the Ulster holds more water than the period type core in the Saloon so that has to be a factor as well.
Steve
RE: Four blade fan? - Howard Wright - 17-08-2024
Just found this thread which although doesn’t provide a definitive answer makes an interesting read.
https://www.austinsevenfriends.co.uk/forum/showthread.php?tid=3140
Howard
RE: Four blade fan? - bystander - 17-08-2024
First thing to check for, is it the correct blade - coil and mag are opposite rotation, and the wrong one could cause the problem
RE: Four blade fan? - Howard Wright - 17-08-2024
(17-08-2024, 08:29 PM)bystander Wrote: First thing to check for, is it the correct blade - coil and mag are opposite rotation, and the wrong one could cause the problem
Definitely a coil fan blade for the coil engine
Howard
RE: Four blade fan? - Mark Dymond - 18-08-2024
In general the radiator fan has most effect when the car is moving slowly or stopped. If your car gets hot at cruising speed Id think its unlikely yo be improved with a better fan. But Austin 7s are weird beast with respect to cooling so I may be wrong.
RE: Four blade fan? - Chris KC - 18-08-2024
Sounds like you've already checked the main things Howard. I think Mark is right in saying the fan will have most influence when the car is stopped or running slowly - won't make much difference at cruising speed. That said, it's slow crawls up hills which will most likely cause you to boil.
I have a four-blade fan on my Ulster, and in my experience the car will inevitably boil on pretty much any steady climb in first or second gear, if the climb is long enough. As Ruairidh said, I'm not sure how to quantify any improvement vs a 2-blade. I now finally have a Calormeter which reads accurately (as opposed to one which is merely decorative) and last summer in the mountains found that to be helpful in anticipating when would be a good time to pull over and take five.
The only suggestions I can add are:
1. The closer the fan is to the radiator, the more effective it will be - there should only be say 1/8" - 1/4" gap.
2. Any air which slips around the radiator rather than passing through it is unhelpful, it may be worth assessing whether there are gaps which might be worth discreetly sealing with a bit of foam strip.
3. Water is actually a more efficient coolant than anti-freeze - the difference is small but there is nonetheless a difference. Of course water doesn't contain corrosion inhibitors or delay freezing, so there's a downside.
4. Try a clip-on electric fan?
RE: Four blade fan? - stuartu - 18-08-2024
I’m not sure how relevant my own experience is, Howard, because in my case the car was one of my supercharged specials which behaved rather like your van. With blown cars there are yet more potential causes for running hot and, because the radiator was a modern core which I thought of as new (in fact it was about 25 years old!) I addressed everything else I could think of first, which took quite a long time and made only incremental differences. It was a good thing to do in general but wasn’t the solution. I might say that my IR thermometer showed no cold spots in the core. Eventually I cracked and asked the radiator people locally to check the flow through the core which, it transpired, was very slow. The replacement core dropped the typical temperature in favourable conditions from circa 90c to 78. I could then belt up the long hill on the local bypass for the. Cost of a 2 degree rise in temperature as opposed to the former 8 degrees or more.
In the meantime I had, among other things, improved airflow, made fine mixture adjustments, abandoned antifreeze and added water wetter. They all helped minimally.
It might be worth testing the core but I am sure your suspicions are correct and the core is the culprit. Not cheap to fix if you want a period core, alas.
Good luck,
Stuart