Front Suspension Cylinders - Strip Down and Overhaul

I have rebuilt and refitted the front suspension cylinders. The suspension arms and anti-roll bar went back on the car some time ago. I'm not sure why, but I'd moved on to refitting pipework before I put the suspension cylinders back on. All fitted now.

Front suspension cylinder refitted

Many years ago I'd noticed that the car had an obvious LHM leak coming from somwehere around the left side wheel arch.

Tell tale signs of leaking LHM

I soon realised that the cause was a split boot. Pulling the car apart ore recently I'd found the other boot not leaking but badly craked. Both boots would need changing. I bought a couple of Suspension cyliner rebuild kits from Citroen Classics a few years ago and now was the time to use them. The kits were a mixture of modern-sourced parts - plus a couple of old Citroen parts - the large 'O' ring seals in the caps.

A suspension cylinder rebuild kit

Instructions for rebuilding suspension cylinders were not included in the original manual 814. You can find some instruction in English for rebuilding rear cyliders at Operation Dx.433-3 in earlier manual 518. If you are in search of instructions for front cylinders, you can find these at Operation D.433-3 in volume 3 of French language manual 583. From manual 583, here is the detail of a later style suspension cylinder:

Suspension cylinder parts

In the diagram above:

    Part 11 is the piston

    Part 7 is the sealing nut on the end.

    Parts 6 and 10 are the felt washer and O ring inside the nut.

    Part 5 is a thick metal thrust washer

    Part 8 is the white Teflon seal inside part 9, another O ring.

 

Before I started the rebuild, I'd been keeping dust and dirt out of the cylinder ends using the smart blue caps that Peter Bremner made on his 3D printer. I'll also use them again when the cylinders are refitted - but before I fit spheres.

 

With the Ligarex clips removed from the large ends, the boots can be pulled off to reveal the pushrods and end nuts of the cylinders. The pushrods remain attached to the boots by the Ligarex clips at the other end.

Pushrods and cylinder nuts revealed

Unlike the rear suspension units, the pushrods and ball bearings of the front units are inside the rubber gaiters and lubricated with hydraulic fluid. The cups, rods and pins of the front suspension cylinders are different to those of the back and I don't know how readily available they are.

 

The nuts that close the ends of the cylinders and hold the seals in place are screwed up pretty tightly. The technique is to carefully grip the nut in a vice and then remove the body from it by using some kind of tool around the boss on the other end (where the hydraulic pipe connects) to turn the cylinder body. The manual recommends wooden jaw liners with a 'V' cut in each.

The manual recommends soft jaws in a vice

You can't grip the nut too tightly in the vice for fear of distorting it and pinching it on to the body even more tightly. And there is the risk that if that happens and you manage to get it off - it won't go back over the piston and/ or seal properly.  Unfortunately, if the vice isnt tight, the nut twists with the body as you try to rotate it. A bit of trial and error is needed to find something to line the vice jaws so that you don't need to tighted the jaws too much but still have enough grip on the nut.

Seperating the nut and cylinder

I used soft aluminium jaw liners and some pieces of rubber. I wiped the cylinder body down with panel wipe so that the rubber gripped it without slipping. Eventually was able to loosen the nut. 

Loosened end nut on a suspension cylinder

Inside the nut was a felt dust seal. This sat in a recessed groove.

Removing the felt seal from the nut.

 There was also a rubber 'O' ring that seals the nut to body join.

Seals inside the cylinder nut

Beneath the nut was a thick thrust washer over the cylinder piston.

Thrust washer (on the piston)

The thrust washer and piston were removed. Inside the circumference of the open end of the body was a white Teflon seal - within an 'O' ring that sat in a recesed groove.

White Teflon seal and 'O' ring in the cylinder end

These provide the seal againt the massive hydraulic fluid pressures at play in the suspension system. Some leakage was always anticipated - which is why the rubber boots have a return line back to the reservoir. It was at this point that I found this.....

That's a bit blurry. This is better. 

Do you recognise it?

It's a thin sliver of hydraulic pipe seal that has found it's way into the suspension cylinder. These get 'shaved' off the seals by the threads when the pipe flare nuts are screwed in or removed. When working on the car, if you disconnect hydraulic lines you need to remember to remove and replace old seals - but also to fish out any slivers of rubber. If you don't these can compromise the working of various slide valves and they can block pipes. In my case, this sliver would have found it's way back to the reservoir from the cylinder and been picked out by the filter.

Here are the parts of my two cylinders laid out.

Suspension cylinder parts laid out

The instructions for the old style rear cylinders in manual 814 warn that several parts and paired and shouldnt be muddled between cylinders. I wasn't sure that was the case with the newer design front cylinders but it didn't hurt to be cautious and I put a couple of discreet marks on things to help ID them.

I carefully marked the parts to help ID them

All the parts were cleaned in petrol and I put the pistons and bodies through my ultrasonic cleaner.  I gave the piston a light polish to make the surface that little bit smoother - hoping it would reduce wear and tear on the new Teflon seal.

 

I didn't bother to disassemble the push rods as I wasn't sure whether replacement pins were available. That's when I found this.... the cups and pins on the pushrod ends were different. 

Different cups on the pushrod ends

Both the cups and pins are different. For the pushrod on the left, the 'fat' pin sits in a slot and then a clip around the circumference of the cup stops it slipping out. The ends of the 'thin' pin of the other pushrod sit in two holes. The difference in pin diameter also means that the pushrods themselves are different. Overall there was about 3mm difference in overall length - partly attributable to different cups but also partly down to different length pushrods.

Two pushrods, two lengths....

A bit of a trawl through the parts manuals revealed that there seems to have been a change in parts late 1970 - for the 1971 model year cars. The shorter rod (right hand side in my photo above) looks to be the original 1968 pushrod from my car, whereas the other one is from a 70s car. My receipts show that I did have a cylinder replaced back in the day, but I can't remember why that was necesary. Anyway, different they were!.

Refiting is the reverse of disassembly. The new felt seals need to be soaked in clean LHM for a few hours before being fitted in the nuts.

Soaking the felt seals in LHM

 I fitted them in the recesses in the nuts - making sure they were not twisted and sat squarely.

New felt seals fitted

The 'O' rings were brushed with LHM and also fitted inside the nuts.

'O' ring for the nut - an original spare part

Rebuilding is pretty straightforward and some may not bother with the workshop manual instuctions - especially if they are in French. However there is a particular  - and simple -  technique for safely fitting the white Teflon seals without damaging them. 

Teflon suspension cylinder seal

I have seen elsewhere on the internet, photos of people trying to fit the Teflon seal by inserting them in the cylinder bodies with the 'O' rings and then trying to push the piston through the middle. With that technique there is a danger that you fold or twist the Teflon seal - causing a crease and ruining it. Here is how the manual says it should be done - and it worked:

 

The rubber 'O' for the cylinder body was brushed with LHM and fitted in it's seat. 

Rubber 'O' ring in the cylinder body

The piston was brushed with LHM and the teflon seal was carefully slipped over the open end of the piston.

Teflon seal on the piston

The piston, smeared with LHM, was carefully slid into the cylinder body. The top of the piston extends from the cylinder and so the Teflon seal was still visible at this point. I moved it down the piston to the rim of the cylinder - where the 'O' ring was sitting.

 

Next the thrust washer was brushed with LHM and slipped over the piston. Carefully pressing down evenly on the thrust washer pressed down on the Teflon ring which suddenly 'popped' into place  - between the piston and the iinner circumference of the 'O' ring seal.

As if by magic, the white Teflon seal was fitted

Taking care not to twist the felt seal, the nut was slipped over the piston and screwed up hand-tight. I slipped the nut end back into my vice - again taking care not to over-tighten it. The manual says a force of between 95 Nm and 120Nm sould be applied when tightening the body to the nut. I had no way of measuring that directly so I tightly gripped a large hex-headed nut in another vice and set a torque wrench to 100Nm to get an idea of what applying that force felt like. I then tried to apply approximately the same force through my adjustable spanner. It was all guess work and I can only really say that I felt I did the nut up pretty damn tight.

 

I painted a green band around the top of the cylinders. Why? Well I needed to repaint the extension piece that fits to the top of the left hand cylinder anyway. But I don't really know why I painted the bands -  other than that there were signs of paint when I took mine apart and I wanted to take them back to the state I think they would have been in originally.

Extension piece and painted band

I'd bought a single replacement suspension boot from Chyparse -a parts supplier in Holland -  back in about 1998. I'd never gotten round to fitting it(!). Now that I needed to replace the pair, I bought two new ones. The various parts sellers often sell a cheaper  'standard' quality version and (because the 'standard' ones aren't very flexible and don't last), a better/ best quality version.

 

The pair I bought most recently were 'best quality' apparently. Now I looked at them, i discovered they weren't a 'pair' at all. One was noticibly softer than the other which was stiffer and less springly. I suspected this harder one might actually be a 'standard' quality one....The old Chyparse boot was closer in feel to the softer/ more flexible of my new 'pair'. What to do? In the end, I decided to fit the two new boots and see if - as suspected - the hard/ less flexible one gave in first. If it does, I always have the Chyparse gaiter as a spare. I also decided to refit the two different suspension pushrods and cups.

Not a pair........

With my decisions made, before I fitted the Ligarex bands, I did a 'trial fit' of the cylinders on the car. It's important that the boss where the hydraulic line joins the cylinder is lined up with the hydraulic pipe. That should be pretty straightforward if you loosely refit the pinch bolts that hold the cylinder in place - as they will line up the cylinder. On my car, on the left had side the boss faces backards - towards the cabin. On the right hand side the boss faces forward towards the bumper. Relative to the cylinder position, it's also important that the slot through the cup of the pushrod is lined up to the split pin holes in the suspension on the car. With the boot joing these two parts together, there is one last check to make: that the overlflow outlet of the boot is lined up with the rilsan overflow pipe on the car.

 

With the alignments made, I fitted the Ligarex bands. Over the gaiters themselves, I fitted new rubber belts so that the Ligarex bands did not bite into the boots.

Ligarex bandings fixed

The only fiddly bit of fitting the cylinders was fitting the split pins through the cups at the bottom. I used new split pins but they were a tight fit in the holes so needed to be lined up perfectly. 

Split pin at the base of the suspension cylinder

With that done, there are two bolts and lock nuts that hold the sides of each cylinder. These are not meant to be done up tightly. These have pointed end. They should only be done up hand tight so that the pointed ends engage in the dimples in the cylinder bodies. Then the lock nuts are tightened.

If I get a suspension leak from one or other boot, I have a spare to fit. When I'm setting up my front anti-roll bar, if that proves difficult then I will have to try and remember that the two suspension pushrods are not quite the same length.