Hydraulic Gear Selector - Strip Down and Overhaul (Part 2)

In my last post I covered how I stripped down and rebuilt the main hydraulic gear selector - the 'gear brain'. In this 'part 2' post, I'll cover how I stripped and rebuilt the  gearchange speed regulator. It's a steel bodied, broadly cylindrical unit bolted on top of the gear brain.

The gearchange speed regulator, on top of the 'gear brain'

I'd got as far as seperating the regulator from the main 'gear brain'. 

Gerachange speed regulator, on the gear brain

 Dismantling and rebuilding involves giving the insides a good clean and replacing the rubber ring seals under the hex heads.

The gearchange speed regulator was introduced to deal with changes in fluid temperature and pressure that would otherwise alter how the gear brain responded. Inside, it looks like this.....

The numbers in brackets relate to the part numbers in the rebuild instructions in English manual 518. But there is a 'but'....

 

At this point I need to say that I love English language manual 518. As well as a digital copy, I have two printed copies distributed around the house. It contains loads of information not in later manual 814. It's an essential companion if you carry out work on your DS. Here's the 'but'....as explained in 'part 1', the gearchange rebuild instructions in English language manual 518 contain errors. And those errors are also in the section covering the gearchange speed regulator. I think it was 'Faulksy' over in Australia that pointed this out.

 

It's helpful to set up a couple of conventions so that it is clear what end of the regulator is being discussed. There is a large hex-headed screw at each end of the regulator body. The body itself is a central cubid shape with a cylinder shape on each end. One cylinder end is long (the French rebuild instructions call this end 'a') and the other cylinder end is short (the French manual calls this end 'b'). The vast majority of work takes place through end 'a'. 

 

With the hex head of end 'a' removed, two pieces slide out -  first a piston and then, after that, a spring.

Initial disassembly of my regulator

 Already this can become confusing if you' are being guided by manul 518. The text is correct, but the photo shows the parts laid out differently. Compare my insides to the (incorrect) photo in manual 518!

WRONG: the incorrect photo in English manual 518

Not only does the photo in manual 518 that the spring comes out before the piston, but also the  piston is the wrong way round relative the two ends of the regulator. By comparison, French manual 583 gets it right. (But note how the part numbers are different).

RIGHT: the equivalent photo in French manual 583

The next task was to dismantle the piston to clean the parts inside. In doing so, I noticed that someone - presumably the machinist or maybe someone from quality control - had put their initial on my piston. Is this a fancy 'J'. Jacques? Just for a moment there was a smell of Gauloise in the air..........

Signed with pride?

Access to the piston is gained from a slotted screw in the end of the piston. I emphasise this to draw a distinction between it and another 'slotted screw': behind the hex screw on end 'b' is a slotted adjuster and it should not be adjusted!

Slotted screw in the regulator body. No - do not tinker!

It's basically a variable 'stop' for the end of the spring. This is factory set for each unit and is not meant to be tampered with. Presumably there were slight variations in body engineering and spring strength and each unit is different. Manual 518 tells you not to alter it, but doesn't really make clear where it is.

 

You might have bought a rebuild kit that contains replacement springs, and feel obliged to replace the spring in the the regulator - reasoning that the old spring might be tired and worn. I would advise against replacing it.

Some rebuild kits contain replacement springs

The spring itself is easily removed from end 'a' but think again before being tempted to replace it as there are no available measurements for setting a new spring up. So you will be no better off.

 

Back to the piston from end 'a'. Undoing the slotted screw in the piston end allows you to remove a surprising large number of very small (and easily lost) parts.

Slotted screw in the piston. yes - undo this...

These are a number of thin discs with small holes in them. You will also have a number of small steel rings. these are spacers for the discs. Last, but not least, you will also find a small circular gauze which lives at the far end of the piston.

Gauze in the piston end

In addition to the gauze, I removed 14 discs, 14 spacers and a washer. 

A surprising number of discs and spacers.....

Note that I also had a washer in addition to the 14 spacers. It's the dirty, blackened ring over on the right hand side in the photo above. The manuals and cutaway diagram make no mention of this washer.

 

This series of discs and spacers are what compensate for changes in the viscosity of the hydraulic fluid. Some discs have the holes through the centre. For others, the holes are offset. This is intentional as the zig-zag passage through the holes is intended to 'frustrate the flow of hydraulic fluid.

 

The holes in the discs are easily blocked and so all the parts benefit from a good clean. The parts can be very gently shaken or tapped out. Don't be tempted to use compressed air or anything sharp to force them out from the gauze end, as you risk losing or damaging the discs (and spacers).

I gave all the parts a good wash and clean in petrol. All the holes in the discs looked clear - which is good becase I wanted to avoid the temptation to poke them through with wire or a needle. The discs and piston were also cleaned in my ultra sonic cleaner. The discs are sufficiently big enough to not get lost at the bottom of the clener and I was careful to keep stock of all the parts. I carefully rinsed and dried the parts and gave the internal parts a brush with LHM.

Reassembly is straightforward but again complicated by both the photos and instructions given in the original printed copies of manual 518....... 

First back into the piston is the gauze, followed by a spacer. Next is a disc. I noted in my unit that, when removed, the last disc removed - disc closest to the gauze - was one that had it's hole offset. This is consistent with the cutaway diagram earlier in this post. It's also consistent with French manaual 583. However (surprise surprise) the factory rebuild instructions in manual 518 contradict this and state that the first disc refitted should have a central hole...... Doubting manual 518 I put mine back together as I had found it.

After the disc with offset hole, another spacer, then a disc with a central hole. I continued like this until all 14 disc and 14 spacers were refitted - making sure as each went in that it was lubticated with LHM and that it sat flat on the layer below. The last piece to go in was the washer/ spacer.

 

This is where manual 518 can be confusing. It's the terminology used. Throughout the procedure, the instructions refer to the two external hex screws as 'plugs'. The slotted adjuster (that should not be adjusted!) under the plug at end 'b' is referred-to as a 'screw', and the slotted cap on the end of the piston is referred-to as a 'plug'....For the assembly instructions, the 'plug' in the piston end is now called a 'screw'. It doesn't sound like a big change, but given the incorrect photo and lack of information about what is where, it's easy to get wrong-footed here. Anyway, I replaced the slotted plug/ screw on the end of the piston.....

Screw (or 'plug') in the piston

All good to go.......

The spring was lubricted and fitted inside the regulator. The assembled piston was lubricated and fitted slotted-screw-end first. In other words, it was fitted leaving the the gauze end visible.

 

A new 'O' ring seal was placed in the recess in the body end. These came with the kit for rebuilding the main 'gear brain'.

New seal for the hex cap

The instructions say this should be fitted over the hex screw, but I put mine in the recess of the body as I felt I could be more confident that the plug then sat squarely and sealed when tightened. 

Which brings me to.....another word of caution here: the two hex screws have the same size threads and hex heads - but have diferent profiles to their inner faces. The screw at end 'b' is concave/ recessed inside. The screw for end 'a' is slotted. Manual 518 is again, not helpful here stating only to "fit the plugs in the same positions as they occupied before dismantling" - but not really reminding you which goes where. French manual 583 is more helpful. It omits this instruction and more clearly states that the parts should be refitted "The cap (1) (recessed body in 'c') placed on the side of the relegation screw, in 'b' ".

In a follow up instruction, manual 518 advises "the plug (1) must enter by hand. If it does not, the spring is out of place". Now I also have a problem with this instruction.......referring to the cutaway diagram earlier in this post, 'plug 1' is at end 'b'. And it covers the adjuster screw that should not be adjusted. So why wouldn't plug 1 go back exactly as you removed it? Surely not for any reason to do with the spring?

I think the instruction in 518 (incidentally the instruction isn't in French language manual 583) must be referring to the hex plug (part 4) on end 'a': if the piston has been put in the wrong way round, or the end of the piston has not engaged with the spring, then maybe the piston sticks out a little too far and stops the hex plug (4) being fitted? I don't know for sure, and none of us should really need to be second-guessing Citroen.

I put a new seal at the other end (end 'b') and replaced that hex screw. Surprise surprise, the plug 'entered by hand'.

 

I fitted the  gearchange speed regulator back on top of the 'gear brain'. Masking off holes and studs, it all got splashed with paint.

After masking and painting

I painted the pair of pipes that fit be wtween the gear brain and speed regulator seperately. remebering to fit new sealing rings in the plate.....

New O rings in the pipe sealing plate

........everything was reunited.

All done

Don't be put off manual 518, it really is very helpful to have. Many of it's sections that aren't in manual 814 are finding their way into digital copies of 814. You can tell which they are because the operations tend to be numbered with a 'DX' prefix. But if what the instructions say, and what your eyes are seeing are different: dig a little deeper. Do some cross-checking. Seek out other advice. Don't take things at face value. Bon chance!