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MG Midget and Sprite Technical - Fan behind vertical flow radiator

Has anyone fitted a cooling fan behind the vertical flow radiator? If so, what type?

There is quite a lot of room there once the engine fan is removed, but the steering rack intrudes at the lower part. It would depend on the fan assembly being thin enough to slip between the rack and the rad.

The 10" Pacet Thinline is thin enough at the edge (see the drawings here http://www.pacet.co.uk/10inchpacets.php), but is it thin enough a quarter of the way up the housing? It's hard to tell. I reckon there is 40mm between the rack and the rad, although its hard to be dead accurate.

Any experience anyone?
Mike Howlett

This might be a better bet as the motor is said to be only 52mm thick http://www.revotec.com/details.asp?ID=96
Mike Howlett

Mike,
MGOC do a Revotec kit for vert rad, G414 £129.95

I've got the kit for the X-flow and the thermoswitch that fits in the top hose is excellent - my mate has one powering a Kenlowe fan - on mine the 10" Revotec fan fitted the other side of the rad is slim bladed and I think too slim, if I ever had to replace it I'd put in a deeper fan, the present one does the job but I feel it's on a bit longer than I want and a deeper one would get the temp down quicker and mine is quite noisy when stationary perhaps because it's enclosed at the front in a box and your would be so bad
Nigel Atkins

Nigel, thanks for your reply. I believe the MGOC Revotec kit fits in front of the rad, and I expect that's what I shall end up doing. But it occurred to me that there is a lot of space BEHIND the rad on my car and since everyone says that is the preferred position for a fan, I wondered if anyone here had actually done it, and how.
Mike Howlett

there's already a fan behind the rad, designed to keep the engine cool. What problem are you trying to fix?
David Smith

My radiator has no shroud, so it was easy to install a 10" fan. The fan support brackets did need a bit of trimming to fit in front of the steering rack. It moves MUCH more air when the engine is at 900 rpms than the stock fan.
Trevor Jessie

David
You must admit that it does not realy do a very good job ;)
It delivers it's best performance when it is not needed and when you need it it does not do a damn thing!

But fitting a fan behind the rad isn't that big a deal is it?
Just go to your local breaker get a fan with the same dia as the original one and fit it behind the rad with some bracing.
Onno K

I can certainly fabricate brackets etc, but the 40mm gap between the rack and the rad could prevent many fans from fitting, that's why I was asking what fans had anyone used - to avoid me buying something that won't fit.

Yes David, Onno is right, the propellor on the water pump is pretty inefficient. When you are tooling along at 70 mph it is using up valuable bhp for no purpose.
Mike Howlett

If you size it the same as the normal fan then it will sit above the rack.
Onno K

Mike,
have you checked that the vert kit fits in front of the rad, it may not (sorry I don't know)

David,
especially this time of year it's beneficial to have the cooling fan only running when required rather than all the time

Onno,
with my luck I couldn't trust a s/h fan as the only fan
Nigel Atkins

"since everyone says that is the preferred position for a fan"

Really ?. I'm very happy with my fan in front.
Dean Smith ('73 RWA)

Yes Dean, you are right, the fan in front works - there are two in that position on my V8 MGB. But the fan behind the rad works better. Why? Because the motor and housing don't get in the way of the air flow to the radiator, and because the windmilling blades don't disturb the air that is attempting to pass through the rad. In terms of overall area, a fan in front of the rad does obscure a significant proportion of the matrix. The fan behind the rad has almost no effect on the air flow when the fan isn't running.

Onno, of course you are right. If I got a fan the same size as the plastic propellor, it must fit - doh, why didn't I think of that!
Mike Howlett

Sorry Mike - I've seen the arguments many many times on here. Of course its not cut and dried either way but I don't agree "everyone says behind is preferred".
Dean Smith ('73 RWA)

Mike,
I follow the reasoning but I think it's a bit swings and roundabouts - I put the following as thoughts only, I don't know the answers

my X-flow system overcools in my car, except when at standstill so the fan in front isn't necessarily blocking or disturbing airflow then

if the car keeps cool without the fan running whilst going 40 mph and above then it's not blocking out enough rad or airflow or disturbing the air flow to worry about

when it's cold it helps to block out some rad and airflow

would spotlights in front of the rad grille block or disturb more aiflow

certainly a fully efficient complete cooling with engine block, rad, heater matrix, hoses all clean and clear, and coolant, thermostat, water pump, fan belt, fan all in good order are a first priority

then of course a secondary cooling system is the engine oil

all just thoughts

Nigel Atkins

I'm sure you are right Nigel. Before I posted the original question I trawled through the archive and there I found lots of opinions that a puller behind the rad was better, hence my presumption. Maybe if I lived in Death Valley it might be an issue, but since I live in Scotland, I suspect a pusher will be fine.

Regarding getting a fan the same diameter as the engine fan, having been out to have another look at the space and measure the engine fan, I realise that the argument doesn't work. The engine fan is 10" diameter, but is bolted on the water pump, so its lower extremeties are BEHIND the steering rack. An electric fan would be mounted close to the radiator and its lower section would be between the rad and the rack, hence my problem. I think I'll just buy a pusher like everyone else!!!
Mike Howlett

since you live in Scotland I suggest you don't need an electric fan at all, as long as the standard system is well maintained.
David Smith

Always struck me as an engineering strangeness to use a cooling fan that gets faster the faster you go, i.e. when you need it the least. Electric fan may not be something you need, but I think that it makes a lot of sense.

As an aside - V-flow rad and oil cooler, any electric fan recommendations. I'm convinced there's not room for a pusher..
OrangeSpyderMan

Not getting to running temp might be a consideration. Below 5 degrees C I put a piece of cardboard with vinyl in front of my grille, like the "winter coats" for mini's and bigger austins. Still contemplating a kind of adjustable louvres behind the grille.
Alex G Matla

David,
as said before removing the engine driven fan means the car warms better in the cold weather

yesterday I was in in the midget air temp around 10 C not much wind chill to consider but my car was showing below its ususual on the temp gauge - I must remember to try blocking the rad grille this year

radiator blinds, Volvo Amazons used to have them IIRC

I know back in the day, for the MGB at least, you could by rad grille 'blankets'(?) that attached to the front of the rad grille and had roll up vents that were held open or closed by velcro, instead I used corrogated card painted black and by doing so I discovered when the car overheated that it had the wrong coolant pressure cap fitted
Nigel Atkins

OSM,
I've no idea what space you have, the Revotec (blowing) are 52 mm at motor which obviously is at centre with a taper to perimeter

personally I'm not a big fan of oil coolers and prefer perhaps higher quality oil instead, I know you may be in warmer climes than over here but at least a (very) few others agree with me, one pointed out that MGBs in England got oil coolers yet those going to the much hotter California did not and that most of them didn’t have the advantage of overdrive either so were driven at higher revs too yet they survived very well

as you’ve probably seen before I think a thorough clean, flush, back flush and flush again of the whole coolant system including engine block, rad , heater matrix, heater tap, hoses then check and replace if required fan belt, thermostat, filler pressure cap and heater valve/tap

that then helps to keep the oil cooler :)
Nigel Atkins

When I first bought my car in '67, it was two years old and it had what looked like a factory fitted radiator blind operated from inside the car by a cable which pulled the blind up in front of the rad. The blind ws on a spring loaded roller, so when the cable was released it went back down again. It was kept in the position it was adjusted to by the fact that the in-car end of the cable was like a bath plug chain and could be secured in the bracket in any position desired. When I had my accident it was destroyed. I've never seen one since and wondered if anyone else had come accross one.

Bernie.
b higginson

Bernie,

My father fitted a home grown blind to several of his cars in the 60's / 70's and it too use the 'plug chain' method of adjustment. I dont know if he copied a proprietary item or if it was his own idea.

Another of his economy ideas was to solder fuse wire in the accelerator jet on the Cortina claiming the loss of performance was minimal whilst the fuel saving was significant!

Getting back on subject, todays Bridges Run was the first with a newly fitted Revotec [in front of the rad] and it came on once in the traffic around Putney on my return trip. The improved heater output was much appreciated on a cold day.
Doug Plumb

Doug,
I must have my Revotec thermoswitch set too low - what area on the temp gauge is your needle when the fan cuts in?

I've been out for ride last three days and on the open road my needle was a lot nearer the C than N
Nigel Atkins

Nigel,

Before replacing my temp gauge recently, I checked the area on the scale where 70c and 100c were recorded at atmospheric pressure [ie ignore the effect of the pressurised system] for reference. Note the two small white dots on the scale at the start of the hot zone that represent 100c.

re the photo:
#1 is ~70c and the normal running temperature both with the mechanical fan and and since removing it.

#2 is the temperature when the Revotec switches off

#3 is ~95c and the temperature when the fan switches on

HTH


Doug Plumb

Doug,
very interesting

I'm on my second temp gauge but both showed the same except this one seems a bit more mobile and inclined to keep near the C mark at some odd times

same as you my car before and after electric in and engine driven out ran at 1

but mine would only get to 2 when stationary by which time the fan would have cut in and then cut off around 1

I had my thermoswitch set just at about 5.30 (as you look at it from the front of the car ignoring top hose angle) just increased it to 6 o’clock the other day but forgot to check the dial readings

your figures tie up with the F gauges as per photo below I lifted from another thread

(nice looking dash on your too)


Nigel Atkins

This thread was discussed between 31/12/2011 and 03/01/2012

MG Midget and Sprite Technical index

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