Fans and Fanbelts

[2F45T4U]

Can't remember the 1850 block but the TR7 one has 4 mounting holes on it for the fan. My TR7 engine has an 1850 fan on it so only uses 3 of the 4 holes. <br>
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That fan will fit an 1850.

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[Leeds Sprint]

I managed to fit a new belt this afternoon. As mentioned earlier in the thread, the broken belt stripped one of the blades off the fan, and I was concerned about putting stress on the bearings from any wobble. <br>
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I have run the fan now and cannot see any new vibrations. All looks very smooth. I'm tempted to run the car with the slightly disabled fan until I have time to try and fit the viscous fan.<br>
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Untill then.... has anyone fitted a viscous type fan with 4 mounting holes to an 1850 with three holes?<br>
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Also can someone post a photo of the mounting plate for the standard 3 hole type 1850 fan? <br>
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Thanks<br>
<br>
Chris

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[2F45T4U]

The TR7 uses a viscous fan, the 1850 doesn't. I have an 1850 fan on a TR7 engine. <br>
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Try it!

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[Jon Tilson]

Tin correctly describes the fab as a Sprint one but I think some more thought is needed on its modus operandi...<br>
If its cold and more viscous surely the fan wont slip? This would then go round faster and prduce more cooling air....not what you want.<br>
I think it just slips at higher engine rpm and spins away at tickover. Thats how the ones on my Spit, Sprint, Landy and Jag work anyway.<br>
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A TR7 oine fits an 1850 but Sprint one wont. But I'm sure the fans can be swapped from mounting brackets with the right press...Have a look at the mounting pins and see if they are the same diameter.<br>
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<br>
Jonners<br>


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[2F45T4U]

Isn't the TR7 fan alot bigger? And with it being viscous wouldnt it free up some power if fitted to an 1850?<br>
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Jonners it depends how the heat acts on it doesn't it? <br>
<br>
"Most cars that have an engine-driven cooling fan have a thermostatically controlled viscous clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator. This type of clutch is a special viscous clutch, much like the viscous coupling sometimes found in all-wheel drive cars. The fluid in the clutch gets thicker as it heats up, causing the fan to spin faster to catch up with the engine rotation. When the car is cold, the fluid in the clutch remains cold and the fan spins slowly, allowing the engine to quickly warm up to its proper operating temperature"

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[davepoth]

I think that the viscous coupling in the Torquatrol unit as fitted to the sprint is designed to stop the problem of cavitation. It seems that once the fan exceeds 3000rpm the amount of cooling that it provides actually decreases because of some funny air pressure thing called cavitation. If anybody Remembers "The Hunt For Red October" it's the effect that makes submarine propellors audible at higher rpm. <br>
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<!--EZCODE LINK START--><a href="http://en.wikipedia.org/wiki/Cavitation" target="top">en.wikipedia.org/wiki/Cavitation</a><!--EZCODE LINK END--><br>
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A correctly functioning Torquatrol unit will only rev to around 3000rpm (the drag on the fan blades provides the "Torque Control" and causes the unit to start slipping) but as they get older, they get less viscous, and so the fan can run quicker, causing cavitation and loss of cooling efficiency.

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[george]

you can stop it when it's cold try it when it's hot !!<br>
no dont do it !!!!!!!!!! might get sued for giving thoughts to people who'd just like to see what works cold or hot<br>
<br>
<br>
cold it spins freely (or should)....hot it should lock up

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[2F45T4U]

There you go then, the voice of reason has spoke! <!--EZCODE EMOTICON START :lol --><img src=http://www.ezboard.com/images/emoticons/laugh.gif ALT=":lol"><!--EZCODE EMOTICON END--> <br>
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<br>
So would it be a good idea to fit a TR7 viscous fan to an 1850 engine?

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[Jon Tilson]

Except you cant change the laws of phyics...<br>
and I dont know of a single fluid that increases in viscosity as it gets hotter. So the hotter the fan hub, the free-er it spins....Not what you want so its not designed to work that way. <br>
<br>
I maintain it spins with engine rpm at low revs giving lots of cooling at tickover in traffic. At high rpm, normally coincinding with decent cooling airflow anyway, the fan slips. The temp of the fan hub is largely irrelevent...<br>
as you'd expect as it sits in the airflow behind the radiator, keeping cool with minimal heat soak from the engine.<br>
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If I'm wrong...please convince me.<br>
<br>
<br>
Jonners

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[2F45T4U]

Maybe as it gets hotter the liquid changes viscosity allowing a brake to be applied. eg the solid (wax is it?) holds apart a clutch, when heated up the two clutch faces are able'd to meet.

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[alun n]

I understand it to be as Jonners describes; it isn't there to increase cooling its there to stop overcooling and to reduce drag at higher engine RPM. That is why when its seized its knackered.<br>
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Nice thinking Adam...but no.

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[george]

it's not only fluid theres a few other things inside <br>
if you've got an old one take it apart and see

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[george]

just read a description of it and it does say it's to let it slip at higher revs <br>
perhaps iv'e got it mixed up with bmw's old 5 series type<br>
which did connect when hot<br>


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[Leeds Sprint]

Wow, thanks for such a comprehensive response to my fan query everyone? <br>
<br>
It's all much clearer now! He he......<br>
<br>
Chris<br>
<br>


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[davepoth]

I'd say probably for the best to change it for a new one. The sprint fan can be connected without the viscous coupling, so I would think any of the good fanblades you have will fit OK.

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