Very stubborn A/C clutch plate nut (after pulley broke)

[baro1968]

On my Citroen C4 Grand Picasso (Diesel), the A/C clutch pulley broke into pieces. I'm trying to replace just the clutch/pulley.

What's left of the clutch/pully is a fragment of the clutch plate held by a nut (if I understand correctly), and whatever I tried, I was unable to remove the nut, even after a lot of attempts, and greaser / colling spray. Is there something special about this nut? I've seen YouTube videos that explain you have to properly hold the plate to unscrew the nut. Since I don't have the full plate, I tried holding whatever was left with a visegrip, a pipe wrench and more, but the nut didn't move at all.

More information. After the clutch/pulley broke, the A/C compressor looked like this:


The parts of the clutch/pulley fell onto the bottom mud cover, and here's how they look like after I collected (most of) them:


After so many attempts to hold the plate with a visegrip, the plate became almost rounded, I actually used a hacksaw to cut away some part of the plate base to get a better grip (I guess I went too far) and now the nut started losing some of its hex shape from all the turning, hammering, etc. Now it looks like this:


Please advise - what can I do?

[mickthemaverick]

When you say 'held in a visegrip' do you mean the plate or the nut, and are you referring to molegrips like these:

Mole grip style pliers

If so they are not the best at giving you grip and leverage. I would try using a couple of large Stilson wrenches, one on the plate hub and one on the bolt, like this:

Stilson wrench

With these wrenches the more leverage you apply the tighter they grip the object, whereas the visegrip only grips at a constant rate which you can overcome by leverage.

The other thing to be wary of is to check that your compressor model is not one of the types that has a left hand thread on that nut, unlikely but you need to be sure.

[thorter]

Looks like a small cold chisel job to me. Partially drill a notch in the remains of the nut with a 3mm or 4mm bit to get a start for the chisel, then use a small light hammer to get a sharp impact. (Be sure you know thread undo direction.)

If that fails, try to drill and chisel so as to put a radial split in the remains if the nut, be sure you don`t bend the compressor shaft!

[thorter]

The main problem may be to get a small enough cold chisel these days. Looking at Screwfix and Toolstation it is clear the key UK growth industry is demolition! Another possibility is a small punch, but again few are up to the necessary level of thump.

[baro1968]

Yeh, I tried to use the following tools (see image below).

Strangely, the nut is "only" 7mm (in videos I saw it's usually much larger). Any advise on identifying the exact model/type of the compressor unit? I tried looking for a number on the bottom, but didn't see anything. It's quite hard to reach, but I'd really appreciate any tips on how to better identify the unit (and maybe figuring out I need to turn the nut in the wrong way). I'm not sure I'm capable enough to do a small cold chisel job...

Tools:

[mickthemaverick]

As you have already ruined the nut it will have to be replaced so it won't hurt to try turning it the other way with the stilsons on the nut and the visegrip holding the plate. If that shows no sign of moving then :
Another option might be to use a nut splitting type tool like this: https://www.ebay.co.uk/itm/285648753565 ... 0W4XSYM37X
but you will of course have to find one that will be small enough for your nut. If you go there, then there will be the chance of wrecking the compressor shaft and having to replace the compressor entirely so be aware of that.

[RichardW]

Need to get the compressor off really so you can see what you are doing / get access. Of course that will mean getting the AC discharged...

[mickthemaverick]

As Richard says taking it off will necessitate depressurising and removing the pipes. If you decide to do that then remove the pipes one at a time and as soon as you take a pipe off the compressor be sure to plug it securely to prevent any foreign bodies getting into the system while the compressor is off.

[thorter]

It may be too late, but I find the Vise-Grip Hex Fastener Tool has the best chance of gripping boltheads and nuts securely with minimal damage. You can adjust it to be very tight, enough sometimes to crush an ordinary nut. Good toolshops keep them, and there are several ebay sellers. eg-

https://www.ebay.co.uk/itm/388671714330 ... 04d532b991