With the engine finally installed and running, my attention on XPO turns to the hydraulics. Given the car hasn’t had an engine since 2008, I’m not very hopeful about the hydraulic circuit still being a closed loop. My expectation is large amounts of LHM on the floor. However, there are some steps to take before the hydraulic pump can dispense pressure again.
Hydraulic Spheres
From arrival day one, it was clear that the spheres would have to change. Some of the green suspension balls were not the right size for the Citroen BX 16Valve and looked less new.
I suspect, at some point, the original sphere was replaced with this to keep the oil in. I believe one of the previous owners had rigged something up to run the hydraulics from time to time. Either way, they had to go!
On the offside, the sphere came off with little resistance. I have a range of “Get The Fxxx Off” tools for spheres, but this one pretty much came off by hand. The rest would not be so hospitable.
Onto the sphere tester, and unsurprisingly, there is no pressure left behind the diaphragm. The degradation was so bad that the diaphragm had come loose inside the sphere and rattled around freely.
While the nearside sphere was much newer, it was far less interested in being separated from the strut. Eventually, the strut top had to come off, and the sphere was encouraged to disengage with more torque.
Perhaps not surprising from the apparent newness, this sphere actually still had some pressure. However, There was no way I would replace a single sphere!
New Spheres
One of the USPs for the BX is the hydraulic suspension and the comfortable ride. While the BX 16Valve is meant to have a stiffer, more sporty ride, flat spheres wouldn’t be much fun to drive. The BX 16Valve has relatively unique spheres within the BX range, which I’ve covered before in All About The Sphere.
A full set of new spheres is the only way to go. These days, aftermarket spheres are the only option. Spheres generally don’t like to sit on a shelf with no pressure, so anything in a Citroen box will likely fail. Although there are a great number of UK suppliers, the turnover of parts means the stock might have sat for a long while. So, my preference is to buy spheres from a dedicated supplier with a high turnover. These spheres came from https://www.sphere-discount.com/gb/
At the time, the spheres cost around £200, including shipping. A relative bargain price. The only downside is thanks to living on Brexit Island, there was an import penalty of £50. So a total cost of £250 for five spheres didn’t seem too bad. Arguably comparable to the price of a UK supplier.
While it did take several weeks for the spheres to arrive, thanks to customs delays, they were not only the right pressure, but just about the right size diameter damper too!
Hydraulic Reservoir
After more than 16 years, it would not be a surprise to find the LHM to be contaminated and the reservoir to have caught some dirt. Draining off the LHM and it was rather yellow, but without many floating particles.
At the bottom of the tank, a reasonably acceptable amount of dirt was trapped under the strainer disc. No metallic parts, but plenty of grit. I suspect a lot of this might have come through the reservoir seal.
Hydraulic Reservoir Restoration
The paintwork on the reservoir was past best, so the decision was taken to completely repaint the tank.
Into the parts washer and the hydraulic fluid tank was cleaned to perfection.
While the tank was being manually scrubbed in the parts washer, the hydraulic filters took a trip in the ultrasonic cleaner.
The worst of the flaky paint was rubbed back and well-cleaned, ready for painting. On the top side, an inflated latex glove was used to stop paint from entering the tank.
A custom can of ‘Moss Green’ enamel paint from Buzzweld was dispensed onto the prepped hydraulic bowl. Colour match is really good to the original Citroen colour. It highlights that the after-market hydraulic spheres are a shade lighter.
Main Pipe
Way back in 2023, I borrowed the main hydraulic feed pipe from XPO for Jazz. The pipe on Jazz rubber through, in part because it was a softer cupro-nickel pipe. Fortunately, I have the flare-making tool for all three Citroen hydraulic pipe sizes.
Hydraulic pipe, nuts and seals for 6.35mm were all ordered from Citroen Classics. The pipe is steel, rather than copper/nickel mix, so it is stiffer when it comes to bend but stronger. The length of pipe is cut based on the parts catalogue length.
The shape is put into the pip using an old, but holed pipe as a template. Surprisingly, the shape match is rather good, if I say so my self.
Pipe nuts are slipped onto the tube and the ends are flared. The replacement pipe is installed onto the car between the FDV and the hydraulic pump.
Strut Leak Back pipes
When the hydraulic suspension strut contracts, excess fluid must be dispensed. Equally, when it expands, the hydraulic cylinder must dispense some excess air. To avoid a puddle, this balance is achieved through the strut leak back pipes. Every time the car lifts up, the rubber pipes bend and flex. In my experience, original rubber replacements would last around ten years, but modern rubber survives for shorter periods. For many years now, I’ve adopted a different approach.
My ‘modern’ solution to the failing leak-off hoses is to implement the system used on the early Citroen BX. When first launched, the BX didn’t use a single-moulded leak-back solution. Instead, an adapter on the strut was connected to the vehicle with individual rubber pipes. This is the same solution I use, only with silicon hose, rather than rubber.
Once the old manifold is cut back flush, some 3.5mm hydraulic barbs are inserted. New lengths of silicon pipe are then cut to a length of 250mm.
The new hose has been installed on the barbs and is ready for connection to the car. From the factory, the two hoses where held to each other with a small clip. I’ve never bothered with the clip on the silicon hoses, with no ill effect.
Strut Tops – Repainting
After so much cleaning and preparation, the strut tops were rather letting the side down. The strut tops connect the hydraulic suspension to the vehicle through an isolating rubber block. Over time, the steel components corrode and look a little worse for wear.
With the hydraulic strut off the car, the steel of the strut top can be cleaned up. Fully dismantling the strut top allows proper cleaning, degreasing and priming.
Several coats of a ‘Peugeot’ black top coat, followed by some lacquer, bring the strut tops to a very fine finish.
Installed back on the car, and the result is night and day difference. However, that rubber is not looking too healthy.
Strut Top Replacement
One of the benefits of taking four years on a three month project is that the parts availability can change. In some cases, once common parts become less available. But in rare instances, new products come to market. And that is exactly what happened with XPO.
Around three months after painting the strut tops, Chevronics in the UK launched a new range of brand-new strut tops. I’ll cover the strut tops in more detail in a separate article, but they are perfect, and definitely needed.
When I dismantled the original XPO struts, I found the rubber had significantly degraded. I doubt they even had another speed bump left in them.
As far as I can tell, the replacement parts are absolutely identical to the originals. I suspect they’re made by the same OEM supplier that Citroen used. I expect the modern rubber won’t age as well. However, despite the price, these are a damn sight better than the aged originals.
The hydraulic spheres, struts, and top mounts have all been assembled, and the hydraulic system’s recommissioning is progressing well. At this point, I can’t replace the rear spheres. They are too tightly affixed, and trying to undo them with no hydraulic pressure will cause damage. A task for another day.
Finishing Off
The hydraulic rebuild generally went rather well. Everything generally came apart without damage, and the plethora of new parts made reassembly straight forward. There were a few issues though.
Despite installing the accumulator and the piping, I had failed to notice that the pressure regulator was a little damaged. When the system pressure reaches the target, excess fluid is sent through a plastic manifold on the bottom of the PRV and back to the hydraulic reservoir. But when I came to fit the return pipe, I realised the plastic manifold was completely missing! Eventually i settled on using the PRV from the sphere tester circuit to get me back up and running.
Finally, the day came to refill the hydraulic system. Over the twenty years I’ve been working on and maintaining BX’s, I’ve watched the price of hydraulic fluid steadily increase. Fortunately, my recent journey into the world of tractors highlighted the number of agricultural machines that use LHM+ fluid. A call to a local agri-engineering centre, and I had 20L of PSA spec hydraulic fluid for far less cash than the Total equivalent.
All back together, and with the engine now running, the first hydraulic tests could be performed. I couldn’t properly test the suspension while the car was still on the ramp. However, the brakes worked on all corners after some bleeding. The hydraulic system was reaching pressure, and amazingly, there were no high-pressure hydraulic leaks. The same could not be said for the low pressure, but that is a story for another day!
M
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