Removing a Viscous Fan without the serpentine belt (1998 Land Rover Discovery)

Question

The PAS pump on my Discovery failed fairly spectacularly last week, shedding it's pulley at the side of the road. In order to get at it to replace it, I need to get the fan off, which requires undoing a left-hand-thread nut in the viscous coupling.

The problem, however, is that I can't stop the pulley rotating in order to undo it (it's on it's own pulley rather than being on the end of the crankshaft). Normally this would be held in place by the serpentine belt, but without the PAS pulley I can't refit the belt...

Any suggestions? I can't get anything in there to wedge the pulley...

Edit: It's the big bolt in the middle of this part (thanks Paulster2 for the link):

And it is located here on the car:

The big pulley spins freely. I've tried using the small bolts that hold the pulley on for extra purchase - two of the four came undone (great, I thought!), but the other two won't - because of the hexagonal shape of the big nut, I can't get a ring spanner on them, and an open-ended one just started to round them...

Answer 1

I take it the above picture of the fan/pulley on the vehicle is not your vehicle, but a photo of the same thing from another vehicle?

If it is your vehicle, wrap a belt completely around either ribbed pulley part and hold it on one side to gain purchase (grab both sides of the belt in one place with one hand). Believe me when I say this will give you more than enough purchase to get it done.

EDIT: If you do not have enough purchase by just using your hand, try wrapping the belt around the pulley and grabbing the belt with a pair of Vise-Grips (or other locking pliers), then grab the Vice-Grips and have at it. This should give you enough purchase.

EDIT2: Something like this:

The arrows denote where the Vice-Grips should be placed. Get the Vice-Grips as close to the pulley as possible. Use enough gripping force to grab the belt so it won't slip, but not enough to damage or destroy the belt itself. You can roll the Vice-Grips back on the pulley for more purchase (will sinch up the belt for more grip on the pulley).

If this isn't your vehicle, how much of the original pully is left? If there is any bit of the jagged edge of the pulley, you should be able to get a screwdriver or other longer prying device in between the pulley and the water pump to stop the free motion of the nut you are trying to loosen. Only pry out enough on the pulley to gain purchase: prying out on it harder may damage the main bushing of the water pump underneath, which will cause premature failure.

If all else fails, take the water pump off entirely. This will give you better access to everything. You may even be able to hold the impeller of the water pump still while breaking the fan nut free. Buying a new water pump gasket would definitely be worth the cost compared to the amount of time you've spent trying to get this thing free.

Answer 2

I believe you can improvise over the approach shown in this diagram.

_{(source: m5board.com)}

Instead of using a spanner to 'lock' just one of the pulley bolts, try to use a long implement similar to the "special tool" depicted in the diagram to lock two pulley bolts in place. I have found great success with water-heater mounting brackets since they are thin enough and do not flex under load (plus the grooves were already cut in to wrap around the pulley bolt).

Before attempting to undo the fan clutch nut, I'd advise to let it soak in WD-40/ PB-blaster for a few hours to make for easier removal.

Answer 3

Using the new pump, you are able to determine the size of its large nut. It is either 34 or 36mm across the flats. Using a flat piece of metal, make a flat spanner with a length long enough to extend out of fan blades to fit the nut. With the 'spanner' on the nut and with a engineers hammer, strike the improvised spanner to undo the nut. The inertia of the assembly allows it to come undone. Viscous couple spanners to do exactly the same are available here in the UK for around £5 ($10 ?). Use a dab of Locktite when fitting the new pump, impacting it in the other direction to tighten it. In a workshop with an air chisel, they can be undone by a couple of short bursts aimed at an angle to the nut.