Radiator Update

You might remember that back in the autumn, having secured a replacement from my friend Peter, I had a go at fixing a *tiny* leak in my radiator, with fatal results.....Having worked on the HP pump and steering rack over the last month or so, I found myself back at the point where I could refit a radiator.

Just waiting for a radiator again.....

The obvious solution was just to fit Peter's radiator, but, having killed my radiator, I reasoned that I would then be without a spare if his also turned out to have so leak. Also, the tapped bolt holes on Peter's radiator are different to mine because it's from a later car. yes - the 5mm tappings are 0.8mm not 0.75mm pitch..... 

Spare radiator from Peter

So......instead I took Peter's along to be pressure-tested and did the 'walk-of-shame' back to my radiator shop with my dead radiator and confessed what I'd done. It was a costly lesson. Yes - the radiator leaked anyway but I ended up needing a full re-core when (If i hadn't tinkered) a simple, cheaper repair might have been possible. 

So within the week I was appropriately poorer, but had a lovely re-cored radiator. As such - and despite having an alternative radiator from Peter, I've just gone and refitted that same old radiator again!

Radiator back on. Again....

As it's been re-cored at least twice to my knowledge, I can't really call it my 'original' radiator, but at least it has the right sized screw threads.

Changing the Drive Head on 123 Electronic Ignition

I finally got fed up with the look of my 123 distributor and decided to do something about it. If you read my posts HERE, you'll know that - when fitted - the angle of the 123 distributor and cap was different to the old Ducellier and cap. It now pointed straight to the oil filler tower. 

Largely this was aesthetic but did cause some minor practical niggles. The solution seemed to be to to change the angle of the drive head on the bottom of the 123.

When the rotors of my Ducellier and the 123 were aligned side-by-side, I reckon there was about 15 to 20 degrees difference in head angle.

Difference in drive head angles - about 15 degrees?

I had considered drilling a new hole through the drive head.....

Difference in hole positions - Ducellier and 123 - about 45 degrees?

.......but the diameter that hole would need to be, meant that it would leave very little 'meat' on the head between old and new heads - possibly weakening the head.

I also considered a straight swap of heads between the Ducellier and the 123. Unfortunately the diameter of the shaft through the 123 is smaller than that of the shaft on the Ducellier.

Difference in internal diameter - Ducellier and 123

I could have fitted the Ducellier head just as it was and pinned it in place - but it would have been very wobbly and maybe prone to giving inconsistent timing or premature wear? or both? 

In the end I decided to shim the gap between the 123 shaft and the Ducellier drive head. The 123 shaft is about 10mm diameter and the Ducellier shaft is about 12.7mm, so i bought a short length of 12.7mm external diameter tube that is 1.2mm thick - meaning the internal diameter is just over 10mm. Luckily for me it fitted both parts a treat.

Ducellier drive head on a 123 shaft - plus shimming collar

I made the holes through my new shimming collar only as big as the pin that went through the head and the shaft. That way i didn't introduce any additional rotational free play.  in removing and refitting the drive head, i had to pay careful attention to ensure I refitted the head with the small and big halves of the head in the correct positions relative to the rotor arm. The beauty of this solution is that it's reversible - I can still swap back and use the 123 drive head if I want or need to.

I refitted it and went through the timing process again. Now the distributor cap points more towards the carburettor, but you can see that the catch for the distributor cap is clear of the water pump bolt. the HT lead between coil and cap is not stretched and the other HT leads seem more comfortable around the oil filler tower.

Old 123 distributor orientation

New 123 distributor orientation

What surprises me though - having re-used a foot from a Ducellier distributor - is that the 123 distributor isn't pointing to where the old Ducellier did. I think what this must mean, is that even though the difference in holes through the drive heads is, say, 45 degrees, there must also be a small difference in the angles of the holes through the distributor shafts of about 30 degrees...... The combination of the two (Ducellier Drive head on a 123 shaft) results in a net distributor position about 15 degrees more towards the carburettor than the original Ducellier position.

So - compared to that original Ducellier position - I can have my 123 pointing an extra 15 degrees in one direction OR about 15 degrees in the other direction...... but I can't easily have it pointing where the old Ducellier did. Changing drive heads alone is not good enough. Getting it *just* right means drilling a hole through a drive head, or through a shaft.....

On the 'plus' side though, the clip for the distributor cap is further away from the water pump stud.

I'm going to leave things be I think.

Steering Rack Repaint

 One of the other things I've been able to cross off my list now is a repaint of the steering rack!

Repainted and ready to go (again)

if you read my post HERE, you'll know that  - as I wasn't sure whether the rack needed replacing or not - I simply did an initial cosmetic tidy up. The idea was to save myself work or the cost of a replacement if it was fine and didn't leak. unfortunately, it didn't turn out 'simple' at all. I had a paint malfunction and the colour looked all wrong.

The steering rack colour looked far too bright

Well at last I've rectified that. Investigating the leak in my HP pump meant I was going to have to repaint it. And that meant i was going to have to break out the compressor and spray gun. That being so, I took the opportunity to repaint the steering rack (again) too. I had to go through exactly the same job i went through before. I had to remove the pipework, arms, gaiters and shields, de-grease everything and then key it up for new paint.

keyed-up and all ready to go.

I sprayed it up (again) over the bank holiday weekend.....

Drying......

.... and then re-assembled it (again).

Track rods and steering levers refitted

And it's now back on the car (again). 

A MUCH better colour match....

I'm FAR happier with the colour! 

HP Pump Leak - New 'O' Rings fitted

Over the last couple of months I've investigated - and hopefully solved - the leak from my HP pump.

With the radiator already off the car, I had better access to the bracing bars and hydraulic connections on and around the HP pump and so pulled it off. With the pump on the bench, I removed the pulley and this is what I found!

Not what I wanted to see!

It looks like the leak is coming from around the inner edges of the green closing cup rather than from around the shaft itself. Maybe like this?

Possible leak routes? (part numbers from catalogue 648)

Not sure what I mean? The deflector and its seal (part 37) fit on the shaft like this.

Deflector seal on the shaft

Deflector over the seal

And then there is a thin metal 'closing cup' (a dust cover?) over the deflector and bearing - but it doesn't fit around the circumference of the shaft. its centre hole is considerably larger than just the diameter of the shaft. Its job seems to be to keep dust and grit out of the bearing.

'Closing cup' over the deflector

The grease and hydraulic fluid seems to be oozing from under the closing cup edge - not from the shaft. So it looks to me as though the deflector seal (37) is doing its job but that the seal behind it (part 35) and the seal carrier it sits in, might be the culprit. 

Seal carrier and seal (labelled as 'part 35')

After some investigation, I'd bitten the bullet and over winter had bought expensive accurately sized seals (you can read about those HERE) and so set about stripping the pump. In fact I also stripped my spare pump - reasoning that if it was going to act as a spare, it might as well benefit from new seals. I could also use it as a point of reference to check my previous work. That other pump had broken mounting brackets - so I got a couple of secondhand ones from a D parts supplier. And another three-belt pulley.

I've rebuilt this pump before. I covered it HERE. Disassembly meant pressing the main pumping parts from the end plate and removing the bearing to access the seal carrier hidden behind.

End plate, bearing, spring, seal carrier and seal
(credit unknown)

I couldn't find anything obviously wrong. Yes - I'd fitted the seal carrier the right way up. And - yes again - it's surface was clean and flat to provide good contact to the bearing.

Surface looked good - no burrs

After cleaning everything, I very gently 'dressed' the surfaces of the carriers on some wet and dry paper and did the same with the inner part of the two bearings. I fitted my new, expensive seals to the carriers and fitted the carriers to the end plates.

When fitted in its recess, the seal carrier still popped out (as it had done on the first rebuild) due to the force of the spring behind it - but not nearly so readily as when I'd first rebuilt the pump. A tighter fit was an encouraging sign.

The consensus of opinion is that, as well as the rubber 'o' ring seal needing to do its job, pushed by the spring behind, the brass/ bronze seal carrier itself also has to fit flat to the bearing to create a metal-to-metal seal. As such the bearing and seal need to be flat to one another when fitted.

For that reason - and as before - I slowly and carefully pressed the bearing into the end plate. I used a large diameter socket so that I was pushing on the outer part of the bearing. And as before I stopped as I went and 're-adjusted' the position of the seal carrier from the pin-roller end to make sure it was correctly positioned.

Pressing the bearing into the end plate

This is the view from the pin roller end after the bearing was fitted. At the bottom of the hole you can just make out a sliver of the bronze/ brass seal carrier and the bearing right at the back.

Bearing and seal carrier in the end plate

Everything looked to be in place. Unfortunately pushing the shaft on the bearing from the pin roller end tends to push the bearing back out again(!) so that it needs to be re-seated. Eventually everything was back together.

As well as the special sized seals, I also bought two new replacement big seals for the cases. I'd recalled from when I first re-built my hydraulic pump that it was hard to press the large outer case back over the seals and onto the end plate. Based on a tip I'd tried using a leftover cardboard inner from a reel of duct tape, but it still moved around too much on the domed end when force was applied and wouldn't push the casing on squarely. To hold it steady, anything used to press the casing on needed to fit around the sides of the casing as well as the end dome.

This time I was ready! I bought some clear resin and took a mould of the end of the casing. I set the casing up so that it was level in my mould and about an inch or so deep in the resin - more than just covering the domed end.

Making a mould of the casing end

I left the resin to harden

New tool for fitting HP pump casings....

I used a block of wood to pad-out the shaft end and my new resin tool to press the casing on. The mould holds the casing steady and spreads pressure on it across a wider surface as it is pressed home.

Pressing the pump casing onto the pump

My mould worked really well and made quick work of refitting the covers. After that it was on to priming......

.....and painting

I'd already planned ahead and bought new tab washers for the pulley nuts. One of the pumps pump is back on the car and the other one is sitting on a shelf - just in case it's needed. Once I get the steering rack and radiator back on I can run the engine and find out....

Sourcing M5 x 0.75 Pitch Nuts

NUTS IN MAY! 

I've not posted anything for a while. The winter months were certainly quieter, but since then I've been pushing ahead with a number of things that have now been completed. In fact April and may have been very, very productive months. For a start, I've had some nuts made for use on my DS!

New 5mm x 0.75 pitch nuts

But 'why?' you might ask......Well you probably appreciate that, being Citroen and so French, the DS is assembled with metric sized fittings. These days, the standards that governs the size of metric fittings are 'ISO' ('International Standards Organisation') standards. ISO 261 governs the outer diameter and 'pitch' for bolts/ set screws. A metric bolt that is 5mm 'wide' (has a 5mm outer diameter) and is designated as an 'M5'. ISO 68-1 defines the shape/ angle of the cut threads and 'pitch' refers to the width of each thread. You can think of that as the distance between 'peak' of the thread. 

Metric fittings can have 'fine' or 'coarse' threads - and the finer a thread is, the smaller it's 'pitch' value is  - as there are more turns of thread per centimetre. For example:

• Coarse thread M5 fittings have a pitch of 0.8mm
• Fine thread M5 fittings have a pitch of 0.5mm

Many metric fittings are widely available in DIY shops or on line and it's not at all hard to find M4, M5, M6, M8 and M10 fittings. And with a little more effort you can find these sizes in either coarse of fine thread. You'll see bolts for sale advertised as 'M5 x 0.8' for example - that's an 5mm wide bolt with a coarse thread. 'M5 x 0.5' would be a 5mm wide bolt with a fine thread.

The Citroen DS is typically assembled with a large number M5 but also M7 and M9 sized fittings.....For late Ds, you can easily buy M5 hardware, but M7 and M9 are harder to find. The DS parts suppliers have these but they are very expensive per item, compared to the more common and widely available sizes.

You can even buy new M5 and M7 bolts with the little symbol on top - just like the original ones used by Citroen.......

Replica Citroen set screws in M5 and M7

If you have a late DS you are probably blissfully unaware, however if you have a pre-April 1970 DS you have an added complication: Citroen only adopted the 'ISO' standard for thread sizes in April 1970! Prior to that date, Citroen used fittings made to the 'S.I.M' standard. (I haven't even been able to find out what 'S.I.M' stood for....).

Here are examples of the Technical Note' sent out to dealers/ repair agents announcing the change of standards they would adhere to and how they would phase out old stock.....:

Technical Note to German dealerships

American version of Technical Note

If you look carefully, you will see that the note says that for fixtures sizes above 5mm, the threads are about the same and so compatible. But, for 3mm, 4mm and 5mm they are not - the threads don't work together.

Why is this? well taking 5mm fixtures as an example, under the new ISO standard, the coarse pitch of an 5mm 'M5' bolt became 0.8mm. Whereas under the previous S.I.M standard, the coarse pitch had been 0.75mm.

What does this mean?

• If the pitch is 0.75mm, then there will be 13.3 turns of thread per centimetre
• If the pitch is 0.8mm, then there will only be 12.5 turns of thread per centimetre

So that's a difference of about one rotation of the fixture per centimetre. That doesn't sound a lot but, this is what that kind of looks like. Kind of.....

Illustrative purposes only: differences in thread pitch

In practice, if you try to fit a 0.75 pitch 5mm nut onto a 0.8mm pitch M5 bolt, then after just a couple of turns, it will start to get very tight.....And the more you tighten it, the harder it will become. You will only be able to tighten it further by damaging threads - either on the nut, or bolt, or both. 

On a DS - and in terms of 5mm/ M5 fixings - you will have cause to use more bolts/ set screws than you will nuts. And if your car is pre April 1970, 5mm x 0.75mm bolts are available. But like the M7s and M9s, they're not cheap......

M5 (5mm) x 0.75 pitch bolt

Some folk just use a tap to re-cut any welded or captive 0.75mm pitch nuts to 0.8mm to take a modern M5 bolt.

Re-tapping a welded nut

If you do this, you cut off metal and weaken the thread. Take a look at the 'wave' diagram above. It takes about 10cm for the peaks of 0.75 pitch and 0.8 pitch to 're-align'. That means that after about 5cm they are completely out of alignment - the peak of one thread is aligned to the trough of the other thread. If you were re-tapping, then at that point all the metal forming the 'pea'k of the tapped thread would be removed to turn it into a 'trough'.

Of course nuts are only 3mm or 4mm deep - so the threads don't go too far out of alignment, however even over such short distances, re-tapping leaves the fittings wobbly and with less 'bite'. Now 5mm sized fixings aren't really used in many mission-critical areas (other than hydraulic plate joints of course).....

M5s securing hydraulic pipes

......but it does mean that if you are a bit forceful and over-tighten your fitting, the remaining thread in the welded/ captive fitting might strip - leaving you with a bigger problem.....That's not guaranteed - just a 'maybe'.

On older Ds, there are also few 5mm bolts or studs that need/ expect 0.75mm pitch nuts. Here are some examples on my 1968 car......

In theory you could use a die to re-cut the studs to 0.8mm pitch....

Die for cutting male threads

...but in practice you tend not to have the room to use a die. Options then are to:

1. build up a store of 0.75mm pitch nuts from old cars and use those
2. re-tap 0.8mm pitch nuts to make them 0.75mm
3. use brute force or ignorance and make a 0.8mm pitch nut fit
4. seek out any old or new 0.75mm pitch nuts you can find.

Having exhausted option 1, and tried option 2, I became an 'option 4' guy. I searched high and low for a supplier. On that point, I got lucky and managed to buy a load of original NOS Citroen 0.75mm bolts. But no nuts...

You'd have thought that - since new 0.75mm pitch bolts can be bought, that the same suppliers would have nuts. But it seems not!! The closet I came was find very thin nuts used to fulfil a specialist role on a Dellorto carburettors. They were costly and at 3mm, not really deep enough to replace the 5mm nuts used on a DS.

Closest I found - and still expensive

And THAT'S why I ended up having some nuts made!

I was encouraged in this endeavour by fellow DS owner Robert Harris. He approached a few engineering firms here in the UK to see if they would make some nuts up and gave me a few leads to follow up too. These tended to draw a blank simply because of the numbers of parts i was likely to want made. I didn't want to have to have many thousands made and then seek to recoup the expenditure by trying to sell them on. there is some demand - but its very 'niche'. 

In the end I put out a plea on a UK engineering forum and someone hesitantly said they'd be willing to make up a batch. He had a computer controlled CNC machine that could be programmed to make a number of nuts to the same standard and dimensions automatically. We settled on a minimum quantity of 350 nuts......

All of the 5mm x 0.75mm pitch nuts I've seen on my DS are 5mm deep - that's a noticeable difference when compared to ISO M5 nuts - and that's the size I went for. I hadn't found anything other than 5mm thick nuts on my DS, and my catalogue only listed one 0.75 pitch nut.....

.....but I have been told by fellow DS enthusiast Gert Larsen that Citroen also made them in other thicknesses:

• ZD9231900U is height 5 mm
• ZD9232300U is height 4 mm
• ZD9232000W is height 3.5 mm

In all cases, these were just plain steel finish - not yellow cadmium plated. At least that meant that I could keep the cost of mine down by not having them yellow zinc passivated. 

I sent my engineer  my last few 'perfect' 5mm deep nut.......

 ........and set up his CNC machine and ran a couple of new nuts off for my approval. 

They looked great, so I gave him the go-ahead and off he went.

They are here now. The results weren't cheap but - based on the price of the 0.75 pitch bolts that are sold - I felt the 'per unit' cost was acceptable.

A lovely bag of 5mm x 0.75 pitch nuts.....

I only really need to keep no more than 100. I don't have the time or inclination to be selling them at 10 a time, so at the D rally in June I will see if one or more of the DS repairers is interested in taking the remainder off my hands at cost price. That then leaves them room for a bit of mark-up if they offer them for sale..