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Viscous Coupling on radiator fan

Tech Talk for Rover owners.

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Viscous Coupling on radiator fan

Post by Mudrat »

Have many people out there, have modified the viscous coupling unit on the fan so that it is locked solid ie rpm of fan is that of the engine.

I recently locked mine, and last night under hard acceleration the fan seperated from the coupling due to plastic fatigue i think. The release of the fan caused considerable damage in the engine bay, destroyed radiator, all belts broken, considerable dent in the bonnet and the oil and power steer lines where all severed, and to top if off one of the blades sliced open the oil filter. Thus causing total loss of oil in the engine as well. :D

The metal centre section of the fan remained attached to the pully, ie the plastic simply came of the designated mounting plate.

Has anyone else experienced anything like this before, and if not i guess that you shouldn't lock up the coupling - causing the fan to spin at a to high rpm.

Any comment on this modification would be great. Just about to go out and pick up the parts - this time i'll be using an un-modified viscous coupling.

Cheers
Go it or blow it
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Post by HSV Rangie »

not designed to spin that fast.

Have heard of this before.

Michael.
Mitsubishi 2010 NT DID Pajero wagon, Factory rear diff lock, Dual batteries, ARB bar, winch, Mt ATZ 4 rib tyres.
1986 RR.
Custom suspension links etc.
HSV 215 engine.
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Post by TuffRR »

Man that would have made a loud bang. Mine was big enough when i lost one of the fins!!! Luckily, it didnt do any damage to the engine bay.
Range Rover - 4.4 V8, MD Crawler Box, F&R Lockers, 35" Centipedes, 4" lift. Overqualified WebWheeler!!!

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Post by stuee »

Thats gotta suck. How old was your fan? The thermo fan in my vk is fixed but I bet if the engine was even able to rev over 4500rpm (I don't have a rev counter in it so I have no idea really) it would probabley blow up before the fan let loose :D
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Post by trr35l »

my thermo fan was locked and would rev to 3500 and vib somthing bad the whole truck would shake chucked it over my left shoulder and put two electric fans on now revs too 5000 easy more power better sound out the back better to drive to boot no over heating just waiting to see how long they last repco cheapies
rover gone zook here i come
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Post by stuee »

If you don't mind me asking, what size fans do you use? I've been thinking about replacement of the viscous fan in the disco for a while but not sure of the results.
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Post by HSV Rangie »

Ford EL fans.

Michael.
Mitsubishi 2010 NT DID Pajero wagon, Factory rear diff lock, Dual batteries, ARB bar, winch, Mt ATZ 4 rib tyres.
1986 RR.
Custom suspension links etc.
HSV 215 engine.
4.3 diffs.
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Post by p76rangie »

I would think that there must have been something wrong with the fan. I lock mine up every summer and have never had an issue.
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Post by J Top »

I have heard of this before.
I don't think it is the top speed as much as the instant change in speed and load.
I regularly add new silicone fluid to GQ TD42 fans ,if the keep spinning when hot after engine shut down they need a top up, and have never had a problem.
J Top
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Post by Mudrat »

The engine was at peak revs when she went. It was a hell of a bang. LOL. The fan is fairly old, after finding bids and pieces of it on the road, you can see signs of minute old cracks. There is obviously new cracks , but in some areas, cracks appear to be of different colour, thus in my opinion indicate that it had already started to crack, and basically was an accident waiting to happen. I dont think it helped the situation by revving it that hard either.

Got most of the parts today, where abouts can you get get and or order, a new fan. The rangie bloke in town is having difficulty tracking one down. Firstly we ordered one, and after waiting a few hours it arrived only to find that it was the wrong one. Typical really!!! The fan i was running, and thought i'd use again, was an 11 blade job, standard rover i think for the year model (1985). It seemed to be running fairly well with it. Sorry, can't tell you overall dia as the one i have is in fairly small pieces. Will post a dia, once i get the correct one.

Cheers
Go it or blow it
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Post by derangedrover »

If your water pump has the single thread for the viscous coupling, an XF falcon vc and fan fits, just need to trim the fan blades to fit in the shroud. If you trim carefully, ie evenly, there is no balance probs and they are cheap and easy to find.

Cheers
Daryl
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Post by RUFF »

derangedrover wrote:If your water pump has the single thread for the viscous coupling, an XF falcon vc and fan fits, just need to trim the fan blades to fit in the shroud. If you trim carefully, ie evenly, there is no balance probs and they are cheap and easy to find.

Cheers
Daryl


An EB Falcon 10 blade viscus hub is a direct swap for the factory Rover one. Use the Rover blades and there are no mods needed at all. I just replaced mine.
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Post by PK »

I just repalced the thermo coupling on my 3.9 disco as it wasn't driving hard enough when hot. The fan had a crack almost totally through one of the blades so replaced that as well - sourced both from Range Rove. Glad the fan didn't let go at speed!!
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Post by ISUZUROVER »

I remember some threads on pirate about this, apparently it is a big problem with rangie fans when the plastic gets old and brittle.
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Post by trr35l »

i used two 13 inch thermo fans from repco they cover all of the radiator no probs about $150 i think with auto switch
rover gone zook here i come
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