Friday, 12 October 2018

A Quick Word About………Hydraulic Fixings and Seals

I won’t pretend for a moment that this is the definitive article on DS pipe seals, but if you are a DS owner – and so potentially a home mechanic -  it’s useful to have some level of understanding of the kinds of hydraulic fixings and seals you will find on your DS.
Pipe seals........
Download manual 843 or 844 “Hydraulics – Course Notes” if you’re interested in finding out more about the theory and princples of Citroen hydraulics. You can find a link to it at the bottom of the list here:
There’ll be a test on Monday.

Flare Nuts
These are probably the most common and recognisable pipe fixing you will spot on your DS. These threaded ‘male’ ends are found on the ends of individual lengths of hydraulic pipe. They are used to fit pipes to hydraulic components, to junctions, or simply to other lengths of hydraulic pipe.
A pipe with flare nut in situ
The ‘nut’ is the hex nut bit (obviously) and the ‘flare’ is the bulge on the pipe near the pipe end.
Nut and flare
Citroen flare nuts work by compressing a small, tubular, rubber (more about that in a minute) seal in the recess between the flare nut and the item the pipe is joining to. The flare on the pipe end provides a lip for the hex nut to be screwed against so that the pipe is pushed into the receiving piece – with the compression provided by the nut then also compressing the seal around the pipe and into the thread grooves.

Two sizes of nut are usually found on a DS – defined by the gauge of pipe they are used with:

Flare nuts for 4.5mm pipe – widely used on the DS. These have a 9mm hex end.
Flare nuts for 6.35mm pipe – only used in a couple of specific situations/ locations. These have a 12mm hex end.
Citroen type flare nuts
When the 9mm ends rust, the hex can become rounded – making the nut very difficult to loosen. Some parts sellers have replacement nuts for 4.5mm pipes but with a bigger, chunkier 10mm hex ends.
Flare nuts with 9mm and 10mm hex ends - both do the same job
Pipe seals.
The compound used to make the seals for use with LHS fluid cars reacts to LHM. Similarly the compound used for LHM seals is not compatible with LHS. In short use the right seals with the right hydraulic system: seals suitable for use with LHS are colour coded red. Seals suitable for use with LHM are colour-coded green. Just to confuse things, Citroen also made some seals that are colour coded white. These are suitable for use in both LHS and LHM system! 

What I don’t get is that, if they could make seals that can be used in both systems (and they certainly appear as part numbers as far back as 1966), then why did they bother to introduce LHM-only seals at all? Why not all white?

From Parts Manual 562 - 1966
The tool of choice for fitting and removing flare nuts is - a flare nut spanner!  It’s more than an open-ended spanner but less than a ring spanner – but only a bit less.
Flare nut spanners
They have a narrow gap which allows them to be slipped over a pipe, but then have sufficient inner surface area to grip the hex end more than an open-ended spanner would. Less spanner slipping means less rounding……
The spanner slips over the pipe being fitted
Flare Nut Removal
If you plan to completely undo a flare nut, DEPRESSURISE YOUR HYDRAULIC SYSTEM. If you don’t know how to do that then you probably shouldn’t be messing with your pipes. Wipe the area around the nut first to remove any grit and road dirt. The aim is to stop debris falling in the hole once the nut’s removed - or when the pipe is refitted.
Clean away dirt before removing
When in use, it’s all too easy for the area of a pipe immediately above the hex end, to get knocked and become bent. It’s important to avoid this. Firstly because it weakens the pipe, and secondly because it makes removal more difficult: it prevents the hex nut sliding up the pipe - with the risk of thread stripping or pipe bursting.
Bent pipe ends make flare nut removal and fitting more difficult
Flare Nut Fitting
Whenever you undo a flare nut, it’s good practice to replace the rubber seal before doing it back up again as the seals get chewed up and might not provide a good seal second time around.
Chewed up seals after removal - note loose slivers
Before fitting a new seal, it’s also good practice to check the female receiving thread. This is because thin slivers of the old seal tend to be sliced off when the nut is fitted and/ or removed and these remain trapped in the threads. These need to be removed otherwise they can prevent any new seal fitting properly and/ or may get into the hydraulic circuitry and cause malfunctions and blockages.

The correct way to fit a flare nut is to push the pipe seal on the pipe end first, leaving about 2mm of pipe end exposed. This exposed pipe end is to help ensure that the pipe engages correctly in the receiving aperture. 
Place the seal on the end of the pipe
I dab the appropriate hydraulic fluid (LHM in my case) on the end of the pipe and the seal before fitting. I also dab a little fluid in the receiving hole. 
Fitting a pipe with seal
When the pipe is pushed into the receiving aperture, the exposed pipe end locates and the seal rides up and partly over the flare. Tightening the flare nut draws the pipe further into the aperture and compresses the seal in the threads below the nut.
The pipe is located in the fitting
Once located, you should be able to  tighten the nut by hand by at least a couple of turns and engage it.
The flare nut should be able to be easily turned by hand
If you cannot, it either means that the pipe (and so the nut) is not in straight, or that the pipe and seal have not been pushed far enough into the receiving hole. Once located, use a flare nut spanner to tighten the nut down. It does not have to be too tight. Citroen say "moderately tight". Don’t worry if all the thread of the male part is not taken up by the female part.

Flanges and Sealing Plates
Where more than one pipe need to meet in a small area, there is probably insufficient room to allow for tappings for receiving flare nuts and then insufficient room to get a flare nut spanner on them to tighten them anyway. The solution? Terminate the pipes in a flange. The pipe ends are brazed onto/ into receiving holes in a flat plate (the flange). 
Gear selector pipes terminating on a flange plate
These flanged pipes are often found to have a green plastic tag attached to one of the pipes. I believe that this indicates that the pipework joins at the flange have been pressure tested.
Green pressure testing 'tell' on a flange pipe
The receiving holes continue through the flange. 
Holes continue through the flange - 3 bolt holes and 5 pipe holes in this case
These pipe holes will marry to orifices on the receiving part or block. But how to provide a hydraulic seal? Solution: a ‘sealing plate’ is used. These plates have larger diameter holes into which sealing ‘O’ rings are placed. The plate then goes between the flange and the receiving part.
Sealing plate with 'O' rings. Note the white markings
Sealing plate in use on the CRC
The thickness of the sealing plate is less than the thickness of the ‘O’ rings – meaning the 'O' rings are compressed when the flange is bolted down – so creating that all imporant hydraulic seal around each hole.
Flange and sealing plates on gearbox pipe

Saturday, 6 October 2018

Dressing The Engine (Part 3) - Ancillaries, Pulleys and Belts

Fitting The Ancillaries
As several functions of the car are belt driven, fitting the ancillaries means aligning them and, more importantly, their pulleys.

The first job was to mount the ancillaries: HP pump, centrifugal regulator and alternator. While I had the access, I used a ‘Mirex’ buckle to connect the main LHM feed hose to the top of the HP pump, before introducing it to the car. 

I’d already cleaned and primed the bracing bars for the HP pump and centrifugal regulator several years ago. These now got a coat of black paint. Similarly, I had already zinc plated the various nuts bolts and washers. I’d taken several reference photos to show how these, and the spacers and bushes, fitted on the bracing bars.
Before: Centrifugal Regulator - September 2015
I couldn't fit the drive belts at this stage so just set the approximate positions of the ancillaries and their bracing bars.

With the HP pump fitted, I was able to refit the 6.35mm pipe to it from the pressure regulator. 
Hydraulic Pipe to HP Pump
In doing this, I discovered I had the wrong hydraulic rubber seals. There are two sizes. While the inner diameters are the same, The outside diameter of mine were approximately 12mm. 
Both are 6.35mm seals, but the one on the left is 12mm outer
These are used on the 6.35mm pipe that goes to the brake accumulator. They proved too big, (and so too tight), for the HP pump and pressure regulator. Instead I had to get hold of some correct 10mm outer diameter seals.

Fitting the alternator was straightforward. As each component was fitted, the various lugs and holes cast into the bell housing started to make increasing sense. 

The fitting of the centrifugal regulator was a little more tricky – possibly because of it’s rubber ‘silent bloc’ mountings. As there is some longitudinal movement afforded by the silent blocs, there are a number of spacers and shims that can be fitted to the fixing bolt to give the right position on the water pump housing. 

It was quite fiddly dropping the washers into place and capturing them on the bolt while balancing the weight of the regulator.

As with the HP pump I just did a loose fit of the mounting bolt and bracing bar until I had checked pulley alignment.

I’ve seen several cars with the bracing bar for the centrifugal regulator fitted wrongly – usually upside down. The end with the hole and rubber bush should go at the top.
Reference Photo - Spring 2015: top end of bar - with rubber bush
This then means the slot end is at the bottom. The benefit of getting it the right way up is that the slot is meant to provide an extra mounting point for an extra nut, bolt and bracket to hold the hydraulic pipes that comes from the top of the centrifugal regulator.
Bottom end of bar - with extra mounting bolt
Pulley Alignment
Pulley alignment is covered in Operation DX.231-0 in Manual 518 and Operation D.236-0 in Volume 1 of  Manual 814.

As the water pump is an integral part of the cylinder head, it is regarded as the baseline component from which reference alignment is taken. There are different sources of pumps and the pulley of the water pump is ‘spun on’ to the pump shaft (rather than being bolted) so even then there is some variation in pulley position: if you swap out the water pump, you should really re-check its continuing alignment to other units and, if you adjust one, you probably then need to adjust another…….

For a bvh car the aligning order is as follows:

-        Alignment between water pump pulley and large grooves of camshaft pulley
-        Alignment between waterpump pulley and alternator pulley
-        Alignment between small grooves of camshaft pulley and HP pump
-        Alignment between HP pump and centrifugal regulator.

There are a couple of different Citroen tools for checking the alignment of pulleys. I used a homemade alignment tool.

The drive belts are 9.5mm width. I had bought some 8mm rod (so that it would sit comfortably in a pulley groove) and (having checked that the rod was straight and true), bent one end (carefully) about 170 degrees around a spare pulley from a centrifugal regulator to give something of a parabolic curve. 

Having shaped the rod, I then re-checked it on a flat surface to make sure that the curved part and long end were still flat/ true.

The hook-shaped end meant that the rod would settle and sit in the groove of a number of different sized pulleys in at least two places – which reduces wobble/ freeplay  and so increases the likelihood of it being  perpendicular to the pulley shaft. As it is the baseline component, I thought about forming it around an old water pump pulley - but then that curve would have been too big/ loose for fitting to the HP pump and centrifugal regulator.
Tool Fits Other Pulleys Too
Water pump to camshaft pulley: My home made tool was slotted over the water pump pulley as it was the smaller of the two. I already had a shim on the shaft between the bearing and the camshaft pulley pulley and found that still gave the right alignment with my new water pump.
Camshaft Pulley Alignment
Water pump to alternator: alignment here was also fine. so far, so good.....
Alternator Lined Up Okay
Camshaft pulley to HP pump: The alignment tool was slotted over the the back grooves of the camshaft pulley. The HP pump was out and needed shimming........
The HP pump, and so its pulley, was out of alignment
I temporarily put a couple of washers between the pump and the mounting log to get the correct alignment, but I plan to get washers with a larger outer diameter to provide better support for the pump.
Temporary shims on the HP Pump
HP Pump to centrifugal regulator: Lastly, the tool was fitted on the HP pump and aligned to the centrifugal regulator.....
Checking the alignment of the centrifugal regulator
If the HP pump was out of alignment, then it probably meant the centrifugal regulator was also out of alignment. Yep......but not as much as the HP pump had been.
Regulator Pulley Was Out Of Alignment
The centrifugal regulator has a spacer behind the front mounting point. These were available in several different sizes, though I didn’t have a bag of these laying around. If – to get alignment – the spacing at the front is altered, then you also need to vary the shims and other washers at the back mounting point. In my case I needed to move the regulator forward by taking a couple of shims out from the back mounting point. and putting them at the front with the spacer.
Shims on the centrifugal regulator
This was quite fiddly to do because of limited access around the bolt shaft. The alignment was checked again.......That was better.
The Pulley Now Aligned
Drive Belt Tensioning
The camshaft pulley and several brackets were removed to allow me to slip the drive belts on. A rummage around in my parts boxes revealed that (with the pair of belts I bought at the DS rally this year) I now had a complete set of new Kleber ‘Ventiflex’ belts......
Drive Belt Set For My bvh car
........including two matched pairs. Result!
Matched Pair of Drive Belts
Being a hydraulic gearbox car, my car has five 9.5mm width belts. These are:

·    Pair of belts (ideally a matched-length pair) between the camshaft pulley and the HP pump (mine are length 955/ 965mm)
Single belt from the HP pump to the centrifugal regulator (mine is length 600mm)
Pair of belts (ideally a matched-length pair) between the camshaft pulley, alternator and water pump/ fan (mine are length 790/ 800mm)

With the pulley alignment checked and set, I slipped the pair of HP pump belts on the camshaft, refitted the clutch cylinder rod, then bolted on the camshaft pulley. The camshaft pulley nut was tightened and the edge of the nut knocked over into the groove in the shaft to stop it working loose.

The remaining belts were refitted and the ancillaries and their bracing bars re-adjusted to provide a little tension on these.
Pulleys Aligned and Belts Fitted
All Belts On
After: Centrifugal Regulator - October 2018
Although the belts were now on, I will do a ‘final fix’ of these components later in the build. The order for tensioning the drive belts and their respective tensions is given in Operation D.236-0 in Volume 1 of  Manual 814 and/ or Operation DX.231-0 in Manual 518

Monday, 1 October 2018

Dressing The Engine (Part 2) - Fitting the CRC and Weber Carburettor

These two major components are best fitted at the same time as they are linked via the rotating ‘flector’ wheel.
The CRC and Carburettor Are Joined By The Flector
The flector joins the butterfly spindle on the carburettor to the cam shaft on the CRC so that they rotate in unison
A Flector
It is important that there are no tight or knotty spots when the flector is rotated. Two alignments needed to be checked – the horizontal alignment of the lugs that slot into the flector and similarly the lug alignment when rotated to the vertical plane. The process is covered in operation DX.314-1 (paragraph 47) of manual 518.

The following checks were carried out with:

·       - The CRC setting pin correctly engaged
·       - The ‘finger’ part of the CRC and it’s bolt loosely put on the CRC shaft.
·       - The fibre spacer (and any intended gaskets) under the carb
·       - Both units loosely bolted into place.

I set the horizontal alignment first. In the idle position, the two lugs on the carb spindle should be in the horizontal plane and needed to be level with the lugs of the CRC control lever.
Checking horizontal alignment.........
If they are not, then the technique is to either put thin packing pieces between the CRC unit and it's seat on the manifold to raise it, and/ or raise the carb by adding a paper gasket under it. To raise my CRC unit slightly I made several shims from thin pieces cut from the lid of a tin of mackerel, and with suitably sized holes drilled through them! I rechecked alignment to make sure the two  pairs of lugs were level.
..........and re-checking horizontal alignment
I next set the vertical alignment. I turned the carb accelerator spindle such that the lugs rotated through 90 degrees. I similarly rotated the control lever of the CRC. Both sets of lugs should be parallel and in the same plane. If not, the technique is to slide the CRC unit slightly forward or backwards to align the lugs. 

Once I’d found this point, I tightened up the CRC bolt under the inlet manifold. With the CRC unit now fixed in place, I removed the carb and got ready to bolt it in place. I allowed the carb spindle to return to the idle position – meaning the lugs were in the horizontal position again. I slotted the flector wheel over the carb lugs and, with the CRC setting pin still in place, married the lugs on the CRC control lever to the other pair of vertical slots on the flector
The CRC control lever was slotted vertically into the flector
The alignment is done with the pairs of lugs touching, but when the lugs re engaged in the flexor they will overlap. Before bolting up in this position, I therefore slid the CRC control lever along the shaft towards the flector. You don’t want the flector to be loose, but neither do you want it pinched tight. When I found the position I was happy with, I tightened the CRC control lever to the CRC shaft....... 
Lugs Engaged - But Don't Pinch The Flector Too Tight
........and bolted on the carburettor.

I was then able to remove the CRC setting pin and fit the rubber plug in the hole. I blipped the throttle shaft a couple of times to make sure that everything moved smoothly as it should.
Rubber plug in the setting pin hole
Last step was to bolt the hydraulic pipe plate to the CRC – using new ‘O’ rings on the ‘sandwich plate’.
Preparing to bolt on the hydraulic pipe union
One of the two ends of the hydraulic pipe was routed between the camshaft pulley and distributor tower and connected to the clutch cylinder. The other end (with a female connector) was plugged and will be connected up later in the rebuild.