S4 Electric Fan Mounting

[William2]

Having decided to fit an after market 9" electric fan to my newly re-cored radiator I wanted to come up with a solution that would not involve using the standard "tyrap" method as this has always struck me as being rather crude. I managed to get some aluminium angle section 10mm x 20mm locally that fitted perfectly and just cleared the rad fins and is lightweight and strong. All held in place by self-tappers and M6 stainless nuts and bolts. Hopefully, I haven't blanked off too much of the radiator core to affect the cooling but I am tempted to modify the two struts so that flow of air from the fan blades isn't impeded at all. All up cost of fan, thermostatic switch, relay and hardware was a very reasonable ?60. Anyway, this may be of interest to anyone who is considering installing such a fan.

[Grizzly]

Be very interested how it fits in relation to the bonnet spring, i was looking at fitting a more modern fan to mine but i thought it would foul if centrally mounted?

[TroonSprint]

Very neat, and nice and close to the radiator matrix, as it should be. It should work a treat.

I notice the overflow bottle on the side and wonder if anyone can tell me how these things are supposed to work. Think about it. The radiator cap has two seals, one right under the top and the lower seal that actually closes the radiator and is held down by the spring. If the pressure gets too great the spring is forced up and fluid can pass up and out of the overflow. OK I understand all that.

As soon as the radiator cools a bit, and/or the pressure falls, the spring closes the radiator again. The overflow pipe is above this seal, so how is coolant supposed to get back into the radiator? If there is slight negative pressure in the rad, the seal will be held down even more tightly than normal. As far as I can see the overflow bottle can't work. It will collect coolant expelled, but it can't return the coolant once the system is cool again.

On my MGB V8 the radiator has a plain cap with no spring seal underneath. The overflow pipe leads to a pressurised container which has the sprung cap on top as the safety valve. The overflow container is normally about one quarter full. As the engine heats up coolant flows into the container, but never reaches the top in normal running. As the engine cools the coolant in the container returns to the rad and is able to do so because (A) there is no lower seal on the rad cap, and (B) the overflow container is pressurised so pushes it back.

The Lotus bottle seems like it can't work. Am I right, or am I wrong? Is the bottle simply to collect expelled coolant so it doesn't go on the road?

Mike

[William2]

I didn't think about the bonnet spring, I have assumed that as the fan has a relatively low profile that it would be ok. Can't really check it for sure at the moment as the body is off the chassis. Fingers crossed!

[Grizzly]

As soon as the radiator cools a bit, and/or the pressure falls, the spring closes the radiator again. The overflow pipe is above this seal, so how is coolant supposed to get back into the radiator? If there is slight negative pressure in the rad, the seal will be held down even more tightly than normal. As far as I can see the overflow bottle can't work. It will collect coolant expelled, but it can't return the coolant once the system is cool again.

Your missing the valve in the centre of the cap, this works of vacuum so if coolant is pushed out under pressure and not replaced with anything (remember the coolant is hot so has expanded) the pressure drops so the cap reseals the Coolant system and as the coolant left cools and contracts it creates a vacuum that opens the valve in the centre of the cap drawing coolant back from the catch tank (if you look at the catch tank the pipe should go all the way to the bottom and should be under the level of coolant so the vacuum doesn't draw air back to the cap). Its kinda a self levelling system, works fine if there isn't a coolant leak anywhere.

If all that makes sense

[ericbushby]

Hello William 2,
I fitted a very similar fan to my S3 but I only used cable ties with small pieces of black hose pipe as spacers. It looks better than it sounds, honest.
In my case a central location would have fouled the bonnet spring, so I mounted it as far to the left hand side as I could and it was then possible to fit the spring relatively easily. The S3 has a wider radiator than the original S4 so it was even further off centre.
I only have mine on a manual switch under the dash behind the temp guage.
What sort of thermostat are you using.
Eric in Burnley
1967 S3SE DHC

[Europatc]

It looks very neat William,I just hope that when you're stood in traffic there is enough clearance for the air to circulate. With the aluminium and the fan cover there is a lot of small radiator covered. Happy motoring
all the best
Stuart

[William2]

Hi Eric, I am using a variable temp thermostatic switch available from Ebay for ?20. I am also wiring in an override switch and indicator lamp. The lamp will come on if the switch is operated or when the fan cuts in automatically. Best of both worlds. On the bonnet spring issue, I will report back when the body is back on the chassis.

[William2]

I wasn't happy with the restricted airflow due to the width of the alloy angle. This is the MK2 version which is still remarkably strong even though I have cut away a lot of material.

[elansprint71]

Mk 2 is a very neat-looking solution. wrt the bonnet spring; I removed the lower end of the spring from around the rack and fitted a small stainless-steel fairlead to the fibre-glass in front of the rack, so that the spring was clear of the fan.
This sort of thing: http://www.v-rigger.com/Sailing-Hardware/Bailers/Fairleads

Are you going to use a push-fit "otter" thermo-switch in the rad? If so, I suggest wiring it in with some copper wire as, having had one blow out when my head was in the vicinity, I can tell you that it was not amusing at the time!

[William2]

Yes, I will be fitting an Otter switch but only as a way of plugging the hole. I may well go the same way as you in fitting the bonnet spring further forwards.