Trouble removing viscous fan coupling

Whilst replacing the radiator on my Defender 90, I discovered that there is loads of play in the viscous fan coupling, from which I deduced that the bearing is knackered. So I equipped myself with a decent 32mm fan spanner and a new viscous unit and set about replacing it. The only problem is that the fixing nut won't budge. I am aware that it has a left-hand thread, so have been trying to turn it clockwise (looking from the front of the engine). I've been positioning the spanner and then trying to shock the nut off by hitting the end of the spanner with a lump hammer, but the pulley just turns, along with the fanbelt, crankshaft, etc. I can't see any way of locking the pulley so that it doesn't turn.

Can anyone suggest how I might get the nut loose?

You'd be better off hitting the spanner with a piece of hard wood, something like a hammer shaft, it's speed you need not weight. Also try hitting the nut in the off direction with a punch and hammer.

I've tried the punch and hammer trick but it didn't budge. I'm slightly concerned that the nut is starting to get mangled (it was slightly mangled before I started, which makes me think that someone had a go at this in the past). I'm starting to wonder whether I need to take an angle grinder to the coupling to "surgically" remove it so that I can get a 32mm socket on the nut.

I would carry on as Carrington suggested-sharp whacks is what you need to shock it off-they are frustrating,but give way in the end,normally

sometimes its worth paying someone else to do it

Done it! Having tried very hard to force the nut undone by drifting it round with a hammer and cold chisel, I eventually gave up on this approach and decided to try and split the nut. I drilled a line of three holes on one of the flats, placed the chisel over the holes and then gave it several thwacks with the hammer. Much to my surprise the nut came loose. Even more miraculously, I managed to do this without damaging the thread underneath or knackering the bearing.

Thanks to everyone for their help and advice.

Sassenach said:

Done it! Having tried very hard to force the nut undone by drifting it round with a hammer and cold chisel, I eventually gave up on this approach and decided to try and split the nut. I drilled a line of three holes on one of the flats, placed the chisel over the holes and then gave it several thwacks with the hammer. Much to my surprise the nut came loose. Even more miraculously, I managed to do this without damaging the thread underneath or knackering the bearing.

Thanks to everyone for their help and advice.

View attachment 63752

Click to expand...

if youd hit each flat in the center in turn with a flat ended punch enough times nut will undo by hand,never fails in my experience

Sassenach said:

Done it! Having tried very hard to force the nut undone by drifting it round with a hammer and cold chisel, I eventually gave up on this approach and decided to try and split the nut. I drilled a line of three holes on one of the flats, placed the chisel over the holes and then gave it several thwacks with the hammer. Much to my surprise the nut came loose. Even more miraculously, I managed to do this without damaging the thread underneath or knackering the bearing.

Thanks to everyone for their help and advice.

View attachment 63752

Click to expand...

usefull tip that


ron.