Viscous Fan

[REPLIC8]

The fan on my car was making a grumbly bearing noise and also I could wobble the fan about a bit. I've swapped it for a S/H one I had in the garage. The replacement seems much stiffer than the original, I can turn it by hand but I can't spin it, the old one used to spin about a full turn.
It also seems to make a lot more wind noise when I rev the engine up, I've only run it in the garage with a warm engine.
When are they supposed to slip? I assume my old one was slipping too much but I never had any temperature problems so it must have been doing the job OK.




Andy
1981 TR7 FHC

[busheytrader]

Hi, the same thing happened to me back in the day when my wedge was my everyday driver.

The new viscous coupling was practically solid with no free movement so lots of noise at high revs. The old one had practically free wheeled in comparison but kept the engine cool. I got the supplier to swap over the seized one for one that slipped.

Adam



TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, S/S Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes all round, Anti- Dive, Strut-Top Roller Bearings, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 14" 5 Spokes or Maestro Turbo 15" Alloys, Cruise Lights, S/S Heater Pipes, Replacement Fuel Tank. No Door Stickers. Mine since July 1986, V8 from 1991 courtesy of S&S V8 conversion and big brake kits.

[dursleyman]

Change to an electric fan. More efficient and saves a lot of weight as well.

Russ

1980 TR7 Sprint DHC, 1981 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

[img]http://i1040.photobucket.com/albums/b410/dursleyman/TR7%20web%20picture/IMG_0479-Optimized.jpg[img]

[Maxwell]

Russ, Andy's car is just as it left the factory with, I believe, less than 10K on the clock! Be criminal to stick an electric fan on!

Maxwell [;)]


2.0 TR7 FHC \ Current
1.8 Mazda MX5 \ Current

[Hasbeen]

I fitted a complete new fan assembly to my 7. It is just as you describe Andy.

Give it a firm spin & it will move just an inch or two, maximum, after you let it go. This has not changed in 400/500 kilometers of use.

I also noticed a great deal more "wind" noise for a few days when it first went on. It is probably still just as noisy now, but I don't notice it. I must be used to it, & perhaps run the radio higher.

I fitted this one, at great expense, when the new engine was running hot, due to the new water pump impellor slipping on it's shaft. It made no difference then, so I guess they have enough cooling capacity to work when slipping quite a bit, as they age.

Hasbeen

[FI Spyder]

Mine has some resistance probably goes a blade or two after release. My S/H and NOS spare fans are about the same. If the slip is too light it won't turn too fast (less noise) but then the natural air flow through the radiator will be enough to cool if everything is working right. You just want to make sure the slip is smooth and not rumbley (about to seize).

- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

[REPLIC8]

Taken it out for a test drive, sounds like I'm driving through a wind tunnel, doesn't slip at all. Going to refit the original for now and have a think about what to do. Can't see the point of buying another aftermarket one as it seems they're all crap.
May go the electric fan route if I can hide all the wiring so you don't know it's on there. I could leave the original on to look correct & just run a shorter belt between the crank & alternator. Above all it needs to be usable. [:)]



Andy
1981 TR7 FHC

[Maxwell]

Andy - I have a spare viscous fan coupling that was promised to a guy over a year ago, possibly two!

It still lives in my garage, collecting cobwebs. If you're interested I'll send him a mail to see if he still wants it!

Maxwell [;)]


2.0 TR7 FHC \ Current
1.8 Mazda MX5 \ Current

[REPLIC8]

Yes please Andrew, [:D]



Andy
1981 TR7 FHC

[Hasbeen]

What ever you do, don't refit the grumbling one, at least not if you don't want a new radiator.

These things don't grumble for long, they break off, & spin into the radiator, quite soon after the grumbling starts.

Hasbeen

[busheytrader]

Yes. The same thing happened to a pal of mine back in the day and trashed the radiator

[Cobber]

I just bin viscous fan on sight now, damned things have cost me a few radiators and aren't ever gonna get the chance of doing it to me again!

"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"

80'Triumph TR7, 73'Land Rover (Ford 351. V8),
'89 Ford Fairlane
'98 MG-F, 69'Ford F250.

[Howard722]

It would be good to understand just how a viscous coupling works and why!-here is my understanding of this `black art` thingy and if somebody has real automotive engineering insight then lets hear it please:-

1.The coupling initially gives a softish friction drive to the fan blades and these rotate without real cooling effect with the fan pulley up to about 2000rpm, after this the air load passing through the radiator onto the fan blades starts to act on the fan and slow it down whilst the fan pulley keeps rotating at running rpm. i.e the fan starts to `free-wheel` and any fan load is removed from the engine.
Under good open road driving conditions this is all that happens.

2. Where the viscous coupling earns the other half of its keep is when you end up jammed in a traffic snarl and things start to heat up as there is no cooling air passing over the radiator-the goo inside the coupling ( which I have seen described as either silicon gel or wax??) reacts and firms up the `soft drive` to hard and the fan rotates properly to give cooling to the radiator.

So its a two part story as I see it-it freewheels at speed and gives cooling when hot and the coupling has firmed up!

If you really really know the facts behind these units please share-thanks







Enjoy& regards

[stevie_a]

<font color="teal"><b>Personally i wouldn't muck about, fit an electric fan, i would ignore originality

if it goes it can make a mess of the bonnet

this was my car.</b></font id="teal">






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<font size="4"><font color="green"><i>If it's not broke don't fix it.</i></font id="green"></font id="size4">

http://www.smallbiztranscripts.co.uk

[Hasbeen]

If you are fitting an electric fan, [or 2] do give some consideration to the alternator. On the 7, even in perfect condition, it is marginal to drive the existing load, particularly on a wet night.

I fitted 2 top quality 16" fans to the 8, one behind sucking, & one in front of the air conditioning condenser, blowing. Combined they drew 30 amps. I then had to fit a push to cut out switch, to stop them working when I wanted to start the car when hot.

If I stopped for fuel, they would not be working, but heat sink would see them working when I wanted to restart the car. With that drain the starter did not get enough power to spin the high compression 4.6 L fast enough to start.

Even on the 7, the reconditioned alternator could not keep up with wipers, lights & radio. I had disconnected the ventilation fan, so I could have the flap open with out a fan running. I figured it would have no chance after the air con went in. Both cars got 85 amp units fitted.

Hasbeen