Citroen XM Forum

Just grind and cut back to sound metal then add a triangular piece right over the jacking point and existing layers

Getting close to refitting the rear subframe now after repairing the nearside box section and mounting area. I thought it would be a good opportunity to check the anti-sink sphere while off the car.
. The pipe however refused to undo and broke off leaving nothing to get hold of. I've ordered a new sphere off ebay (Febi brand £35) but can the old one be drilled out and re-used as an accumulator? Depending on the remaining pressure obviously.
. I've also started on the nearside sill, which needs the outer L section repairing. The inner sill has corroded behind but think I've just about caught it in time.
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That sill looks generally very sound, but slicing off the bottom of the rib and welding in a new stip would just as it was originally. Is the bright metal the centre upright, or the outer sill section?

For the anti-sink sphere, I assume the pipe and male union sheared off. You might be able to remove it after applying a little heat, but be wary of the membrane.
You could drill it to the minor thread diameter and use a tap to cut out the rest of the thread, alternatively it might wind out once the centre has been drilled out, then it would be back to useable, alternatively, regas it and use it as an accumulator, or Hydractive regulator sphere.

The brighter bit half way up the spot welds is the outer sill face with the inner (mid?) part of the sill below slightly rusty and pitted where I've cleaned it. I'll make another cut above the spot welds and then butt weld in a new L shaped piece to replicate the original detail, with a few plug welds for good measure.

I tried gently heating the sphere union but that didn't work, so drilled it out to 7mm leaving the remains of the pipe in the hole and no useable thread. I gave up at that point and ordered a new sphere! I don't think the threads will clean up but will have another go. Given that the pipe is only 4.5mm does that mean there is no benefit in drilling a bigger hole, like that of a normal accumulator?

7mm is more than enough for an accumulator, or regulator sphere.

Given the state of the rear end of that car, the front of the sills appear in very good condition.

So the latest problem I've found is damaged threads on the SC/MAC valve. There were a few slivers of thread left so tried shortening the pipe end and seal by 3-4mm, but that didn't work. Fortunately I have sourced a replacement valve and will try helicoiling this for future use. I tried using one of the new pipe unions that came with the car and then realised they were the wrong pitch. Fortunately this was on a K valve and it cleaned up with a thread tap.

My concern now is that by reducing the pipe length is that it won't seal. I read on a D series forum that the hydraulic seal is formed between the metal parts and not the rubber. I'm not convinced about that but if needed I can make up a new pipe.
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I think the seal is a mixture of the pipe sealing against the port and also the rubber seal then providing the final seal for any remaining leak.

After what seems like an eternity the subframe has finally been reunited with the car following more welding, new pipes, SC/MAC valve and anti-sink sphere.

There is still plenty to do including repairs to the sill / floor pan but at least it can be driven in and out of the workshop.

A quick test drive around the yard revealed very hard suspension, a heavy accelerator pedal and working aircon so not all bad!

Repair plate for nearside rear jacking point:

All the loose original underseal was scraped off and 2 coats of Jenolite rust converter applied followed by stone chip and a light coat of paint.

Even my welding looks neat when the stone chip goes on!!


That should keep the rust at bay for a few years!
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After refitting the subframe it occurred to me that it may need re-aligning. Is there a procedure for doing this? I read something about the 2 blank holes on either side in front of the front mounting points but now can't find it.

AFAIK, there is no alighnment of the subframe, the bushings fit accurately enough to ensure correct alignment.

You've made a nice job of welding in that plate and painting the underside. The underbody were never painted in colour, just phospahte dipped and undersealed in exposed areas.

The accelerator cable being heavy will be due to this car being an automatic. The gearbox pressure cable does make the accelerator rather heavy.

I note your post about the thread pitch on the union back-nuts. I suspect they are either Din, or SAE backnuts, not Citroen ones.

Nice hardwood workbench you have there Jon.

Thanks for the comments Will that's good to know about the subframe.

I removed the accelerator cable last night and as it moved freely just gave it quick squirt of oil. The return spring / pressure cable on the engine end is quite heavy so maybe that it is a characteristic of the car as you say.

The underside does appear to have been factory painted, unless it is just overspray from the bodywork? I didn't want it black everywhere so thought I would try and match the original finish. I need to try and stop making extra work for myself.


I found a pair of used front spheres still showing 55 bar so have fitted them. Taking the old ones off required a 3' long bar as they were so over tightened.