Citroen XM Forum

Checked the welding and re-fettled it, then another good scrub with acid and the subframe looked like this.
A coat of anti-corrosion primer was applied to all upper side, and lower side inaccessible when re-mounted, bare metal.
For better access and to make this job quicker, it might have been quicker to remove the subframe completely, but I didn't disconnect the hydraulics, so am doing this in situ.

A coat of red oxide primer to the upper side and underneath the mounting points.
Although there is no corrosion there, I brushed a bit onto the body side mounts and will overcoat with top coat.

A look at the inner rear sills and rear dog-legs shows them to be in good condition. I welded the left rear inner sill as part of putting the car on the road in 2011 and have subsequently rust-proofed the sills and box sections.

I cleaned up some of the loose parts, in particular the subframe mounting bushes, which appear to be perfectly serviceable, so a first primer coat has been applied.
The rubber doesn't seem to deteriorate much, normally failure is delamination due to the surface of the steel corroding.
Two coats of machinery enamel to the subframe.

I scraped, wire wheeled, brushed and acid scrubbed the underside of the body and lose parts and painted with red oxide primer.
The very lead edges of the brake backing disks were holed and thin so I added a small plate to one and wire to both disk corners and welded them up.

There is no need for a complete repaint, so I am only doing areas where the paint is worn out, or areas I know to be susceptible to paint cracking and lifting, such as the seams.
I welded the spare wheel carrier years ago, but the bitumastic paint has worn off, so I am re-painting.

A second coat of anti-corrosion primer and then the first coat of machine enamel applied.
I still have the rear panel corrosion to deal with but, in an effort to avoid mission creep, want to mount the subframe back into the body before dealing with that.

Second coat of black machine paint and two coats of silver for the brake back-plates.

After cleaning out the paint from the threads of the subframe mountings I installed them to the chassis rail and installed the subframe.

I had already checked the underside of the subframe and identified a couple of small areas on the right side where I the outer layer of steel was bulging, so intended to investigate.
I cut the outer layer off, de-rusted and acid cleaned the inner layers, of which these two small areas came up very well.
on the left side there was a third area, which I hadn't noticed originally, but had more internal rust packing and after chipping away at it showed a small hole in the upper layer.
This was really awkward to deal with as access with the trailing arm still fitted was very tight.
Using a tungsten burr via the outer pocket, I cleaned the inner layer, cut a piece of steel and managed to weld it in. The welding is far from neat, as I couldn't see past the welding torch, but I did manage to weld the patch in from both sides.
I should probably have cut a larger pocket in the outer layer to give better access to the internal layer.

The outer layer cut off, showing the rust packing, and after welding and a coat of primer.
I considered removing the suspension ram and trailing arm, but due quite a bit more dismantling and the risk of the Arb bolt threads stripping, decided I could just gain enough access without.
I had pulled the R clip out of the arm and thought it was a good time to add copper-slip to prevent seizure at a later date. These clips are often seized into the arm so much they snap off when removal is attempted, preventing the suspension leg connection being removed from the arm.

I really struggled for good access to weld, so it ended up not particularly neat. If doing this again, I probably would disconnect the hydraulics pipes to be able to completely remove the subframe, then flip it over for underside work. My axle stands were right in the way until I slid completely under the car to be able to face from the other direction.
I removed the spheres and gave all available metal a good wire brushing acid treatment and degrease, then a coat of anti-corrosion primer, reaching right under the trailing arm pivot, which was bare of paint.

Another primer coat and two machine enamel coats later.
As I had removed the hydraulics pipe cover and unclipped them, I checked the pipes for any corrosion and found the black nickel coating had been breached on two pipes and there was some surface corrosion.
The pipe coating has only been affected where the cover "protects" them, the rest are in very good condition. The cover traps grit, dirt and salt, which rubs the coating.
I'll keep the cover on as these pipes are directly in the line of the front road wheel.
A scrub with a wire brush showed the corrosion to be surface only and cleaned them up sufficiently for paint to be effective.
Two coats of anti-corrosion primer.

Two coats of machine enamel onto the hydraulic pipes, which I'll let harden for a few days before re-installing the clips and cover.
This gives an easy opportunity to see how clean the LHM is.
Before re-installing the rear spheres I wanted to check the pressures and paint them. I can't remember when I last filled these.

The corner spheres looked poor due to dirt and rust, but were at standard pressure. I wonder if I over-filled them previously.

The Hydractive regulator sphere was down to 30 Bar, though I hadn't really noticed that when driving.
It appears the last fill was to 52 Bar.
The front corners were at 42 and 43 Bar.
I refilled the rear regulator and front corner spheres to 50Bar each.
As they are the same type, I have swapped the front corner spheres with the new IFHS ones from the estate to see if there is any difference in ride quality.

I then wire wheeled and painted a first coat onto the three rear spheres, with the worst paint I have ever used. I can't recommend Wickes water based direct to metal paint.
As all direct to metal paints, it is designed to be sticky, but it has no flow at all and seems to cause little dried balls within the paint as it is drying while being painted.
I'll rub down and give a second coat, but having used the same paint on my re-gassing rig, don't hold out much hope of a decent finish.