43 replies to this topic

[Readers14]

Is it absolutley necessary to fit a fan spacer?

The reason I ask is that I have removed & replaced the water pump & fitted new larger diameter pulley.

When I have come to re-fit the fan, there is just enough length on the bolts to comfortably tighten the pulley & fan without a spacer.

 

If I fitted a spacer, then there would be only a few threads engagement on to the pump.

[nicklouse]

lets put if like this the spacers (there is more than one thickness) are there to position the fan blades in the correct position to give maximum air flow through the radiator.

 

yes I would fit the fan in the correct position and the right way round. (smooth side to the engine).

[Spider]

The spacers, thickness and number thereof is, ask Nick mentioned, to position the fan in the best possible place.

 

That's with the fun just inside the Cowling, but there's a bit of a juggling act that needs to be done here too.

 

You also need a minimum 1/2" clearance from the fan to the Harmonic damper and also the Radiator itself so that the normally simple job of fitting a fan belt doesn't turn in to an all day ordeal.

[Readers14]

So before I replaced the water pump, a 4mm spacer had been fitted front & rear of the fan.

I think longer bolts had been fitted, as I bought the correct bolts from Minispares & now there is no where near the same thread length as before.

 

For now, I will leave the spacer off & assemble the radiator with cowling. Then check where the fan sits in relation to the cowling/radiator

[nicklouse]

with the 4mm spacer there is normally just the one fitted and that is between the pump and the fan. there is no point or need to have one at the other side unless the bolts used were 4mm too long.

[SolarB]

I ended up making a custom spacer to move the fan as close to the radiator as possible. It actually seems to increase the efficiency of the fan quite a bit if you reduce the gap as much as possible.

[Cooperman]

The fan on a Mini is a ducted fan.
The critical factor is the clearance between the fan blade tips and the circular edge of the shroud. The blade tip must be exactly lined up with the shroud for best air flow volume.
A lot of overheating can be the result of the blade tips not being close enough to the shroud.

[big john]

So what is the optimal minimum distance from the fan to the radiator? Mine is now 3/4", but the motor is pieced together from odd bits and I never knew what the original gap was. 

[SolarB]

Think I ended up with about 1/2 an inch.

It was initially closer but the fan touched the rad and destroyed itself. Luckily the rad survived.

[nicklouse]

So what is the optimal minimum distance from the fan to the radiator? Mine is now 3/4", but the motor is pieced together from odd bits and I never knew what the original gap was. 

to be honest it is where it sits in the shroud. the fan to rad distance can change due to different rad designs and shrouds.

[cooperd70]

I've always wondered about mine. I have a 1990 998 which is completely standard. It had only one owner from new before myself so I'm pretty sure that it's as it came from the factory. However the fan is only partially inside the cowl and quite a distance from the rad. Personally I think it needs a spacer to move it closer into the cowl/nearer the rad.
I think the later minis are all like this...though can't be sure. Older cars have different spacers, as well as the inner wing cowl the other side of the rad. On older cars Ive seen the fan is definitely inside the cowl/closer to the rad.
I think if I moved mine closer in using another spacer it would improve the efficiency.

Anyone else have more info on newer minis?

[Cooperman]

The fan to radiator fact dimension is unimportant.

As I said earlier, the key to optimum flow is having the mean blade position in the centre of the lip on the shroud. Moving the fan face towards the radiator whilst the blade tips are not fully in line with the shroud return lip will reduce air-flow and thus reduce cooling.

The Mk.1 2-piece shroud has the lip facing the opposite way from the later cars. Just make sure the fan blade tips are running within the width if this lip.

[Spider]

So before I replaced the water pump, a 4mm spacer had been fitted front & rear of the fan.

I think longer bolts had been fitted, as I bought the correct bolts from Minispares & now there is no where near the same thread length as before.

 

For now, I will leave the spacer off & assemble the radiator with cowling. Then check where the fan sits in relation to the cowling/radiator

 

Respectfully, don't work to the length bolts you have, get it all to fit up correctly, then if need be, get the correct length bolts to make that combination work.

 

The fan to radiator fact dimension is unimportant.

As I said earlier, the key to optimum flow is having the mean blade position in the centre of the lip on the shroud. Moving the fan face towards the radiator whilst the blade tips are not fully in line with the shroud return lip will reduce air-flow and thus reduce cooling.

The Mk.1 2-piece shroud has the lip facing the opposite way from the later cars. Just make sure the fan blade tips are running within the width if this lip.

 

I agree completely with what you've mentioned here in regards to fan efficiency and to add to that, keep in mind, right in the middle of the fan itself, is a dead section by way of the hub of the fan, which is much worse with the plastic fans than the metal ones. If the Fan is too close to the Radiator, there'll be very low (if any) air flow though that part which could end up being blocked off by the Fan Hub.

 

The other aspect, as I mentioned ^ is to be sure you can get a new fan belt in there.

[Readers14]

Respectfully, don't work to the length bolts you have, get it all to fit up correctly, then if need be, get the correct length bolts to make that combination work.

This is understood now.
Not knowing that the bolts were different lengths did throw me, once I tried to fit the fan.
It didn’t help that the previous owner had left a sheared bolt in the water pump pulley!

Edited by Readers14, 28 November 2018 - 07:09 PM.

[Readers14]

Ok, so cowling/radiator mock fitted with no spacer:-

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