engine driven rad fan

[rdssdi]

When I restored my Elan +2 a top priority was removing the anemic two bladed engine driven fan and adding an electric fan. I was told that original +2's had a non shrouded electric pusher fan in conjunction with the engine driven puller. My car did not have the electric fan.

I recently replaced the original electric fan that I had positioned in front of the custom alloy rad. I substituted an electric fan of greater capacity in an effort to get better cooling. It works satisfactorily but not as well as a puller fan would.

My TVR is headed to the upholstery shop and I am turning my attention to the Jaguar MK2 restoration. Again, as with the Elan +2, I am trying to improve upon the cooling. This MK2 will have A/C and will require a great deal of cooling capacity.

The problems encountered are remarkably similar to the Elan +2. There is little room between the rad core face and the water pump pulley. This makes a rad of greater depth and/or the addition of electric puller fans with a shroud impossible. Minimum depth of an electric puller with shroud is around 2 5/8".

What if one considers an engine driven fan and custom shroud. Has anyone attempted to use a Flex-a-lite fan with thermo fan clutch on an Elan +2?

My understanding is that an engine driven puller fan with a properly designed and fit shroud will outperform an electric pusher fan. Is the fragility of the water pump seal a negative determining factor for the +2? I replaced my +2 water pump with a Dave Bean cassette unit.
My assumption is that if it would work for the Elan +2 it would work for the Jaguar MK2.

Bob

[Ross Robbins]

Bob,
I am not nearly as qualified to respond to this as Rohan or Gary might be, but living in Denver with our hot dry climate, which is the toughest cooling challenge there is, I have learned quite a bit about cooling old English cars. Here are my thoughts:

1. A pusher fan of 10" to 12" diameter can move a lot of air, especially if it has a manual switch so you can get it running in advance of the heat loading like before a long climb or entering a congested area. I have successfully solved my cooling issues on both the Elan and Elite as well as an Austin Healey that would not cool any other way, including a Flex-a-ilite fan.

2. The problem with engine driven fans of any type is that they're running at the slowest rpm when they are most needed. An electric fan runs full speed when activated.

3. Make sure you have a way to get ALL the air out of the system or it will allow your water pump to cavitate and reduce the efficiency of the system even though the capacity is adequate otherwise. I found the addition of a swirl pot with a bleed off the top of the water pump lowered my Elan race car temps by 24 degrees Fahrenheit with no other changes. Of course we had tried everything prior to that which we should have done first.

Good luck whatever you choose to do.

[Tahoe]

My S2 had a pusher electric fan when I bought it and it didn't work very well. I designed my own Alloy Radiator, made sure it didn't have any air bypass around the sides or bottom and installed a plastic fan from a Datsun 1600 DHC on the engine. I have driven the car in 95 degree F temps in stop and go traffic and the it never overheats. Pusher fans are less efficient than puller fans, but do work fine. The key is not having air bypass which can cause recirculation and actually inhibit air flow. The fan I choose is the exact same plastic fan I had on my first Elan, and I used to drive it in heavy Southern California traffic all the time without any overheating. Now I live where it's cooler (most of the time) and don't see heavy traffic as much, but when I do in the Summer and I'm caught in the single lane tourist traffic I have no worries. I know many will say don't do an engine driven fan, but to date on 2 cars I've had no water pump issues, and it's one less electric device I don't have to worry about.

[alan.barker]

Bob as far as i know only the +2 early cars had the 2 blade metal fan on the water pump pulley. The +2s model had the pusher electric fan. When i had a 1968 +2 with the 2 blade metal fan the water pump bearing broke letting the metal fan tripan the radiator. I was on holiday at the time in Scotland and had to change the water pump at the side of the road and find someone to fix the rad. At least with the electric fan the is no damage to the rad when a water pump lets go
Alan B

[bast0n]

Bob

I have an enormous pusher electric fan - actually half of a Renault 25 fan - wired to an electronic controller,(adjustable), and a manual overide switch. Also a recored full width radiator which S3s come with as standard.

No engine driven fan as they are noisy and inefficient in standard form.

No problems in traffic in temperatures of over 35c.

Good luck, David.

Anarchy S3

[worzel]

Hi

I can only second David's comment about a Renault 25 fan- if it's the same as the Citroen BX 19 one I've one fitted to my sprint and although a push type unit never any problems overheating (well not during the current weather at least!).

Regards

John

[Andy8421]

Just to expand on a point made above, an engine driven fan can shift much more air than an electric fan, but it doesn't do it when you need it most. Charging down the road at 70mph, all the cooling airflow comes from the ram effect through the grill - an engine driven fan just soaks up HP and gets in the way. Its at slow speed or tickover when stationary that you need the fan, and thats when things get marginal. No ram flow through the grill, and at tickover an engine driven fan doesn't blow much air.

So an electric fan wins on two counts, it blows much more air than an engine driven fan at tickover, and it doesnt waste HP at high engine revs when you don't need a fan anyway.

[alan.barker]

some cars in the past had a viscose engine fan which was controlled by temp of engine.
Alan B

[69S4]

some cars in the past had a viscose engine fan which was controlled by temp of engine.
Alan B

My Landrover has one of those but it also has a big electric fan on the radiator as well. When things get hot there must be a sort of push-me, pull-you cooling system in effect, but however it works it's certainly effective as it never overheats. The rad might have something to do with it as well; for a similar output engine the rad is probably four times the size of the one on the Elan.

[rgh0]

4WD cooling systems are designed for maximum power at zero speed as you work slowly up very steep hills or through thick mud or sand. So the cooling needs in terms of fans and radiator size are much bigger than an Elan that only sees maximum power at high speed or medium to low power when stuck in a traffic jam!!

Technically there is no significant difference between a puller and pusher ducted fan in terms of aerodynamic performance. if no space for a puller behind the radiator a pusher at the front is equivalent.


cheers
Rohan

[Andy8421]

some cars in the past had a viscose engine fan which was controlled by temp of engine.
Alan B

Very true, and to a certain extent that solves the 'stealing HP at high rpm' issue as well, but in order to blow enough air at tickover, you end up with a fan so big that wouldn't be out of place on a helicopter.

[Andy8421]

Technically there is no significant difference between a puller and pusher ducted fan in terms of aerodynamic performance. if no space for a puller behind the radiator a pusher at the front is equivalent.

cheers
Rohan

On the Elan, there is a ton of space in front of the rad, and very little behind. The Elan has a decent size air intake (the grill) but not a lot of room for air to exit behind the rad - hence the factory recommended holes in the inner wing. I have always thought cramming a puller fan behind the rad further obstructs an already cramped space and that it is far better to have a pusher in front of the rad than a puller behind. So if all other things are equal, a puller may be the same as a pusher (which seems reasonable), in the Elan all things are not equal and I would prefer a pusher.

[billwill]

And of course the two-blade original fan is pretty useless and somewhat dangerous so if you want a fan on the water-pump shaft at least find a multi-bladed plastic fan.