Restoration of a 1968 Citroen DS21bvh Pallas: Water Pump Drive Belts

I want to get the steering rack back in the car so that I can permanently connect up the radiator for the last time. But it's all ground to a halt while I wait for some replacement drive belts that I can be happy with. It's been a bit of a Goldilocks time, so let me tell you the story......

Once upon a time - when I was sorting through all my bits at the start of this restoration - I was pleased to find I had a nice set of original 'Kleber Ventiflex' belts for all the pulleys. I even got as far as fitting them back on the engine.

Complete set of drive belts

You can read about that here, but of course that was before I decided I was going to refit the clutch again. Now I'm cracking on with the rebuild, I remembered that the belts that go between the camshaft pulley, alternator and water pump were very tight..... I could barely slip the belts over the three pulleys they were that tight. I was worried they would cause premature wear to the water pump and/ or alternator bearings.

In the parts books, these drive belts are listed as water pump parts - but it was the alternator that seemed to be at the root of my problem. Part of the problem was the bracing bar on the alternator. The alternator was close to the end of the slot in the bracing bar that holds it in position and it couldn't move enough to provide sufficient 'slack'.

Alternator at the end of it's adjustment

Another part of the problem was that the base of my alternator has a little 'leg'......

....that - when fitted - locates against the little step on the side of the block.

Alternator 'stop' against the block

That 'stop' limited how far in (towards the engine) the alternator could be moved. In short, taking the bracing bar and 'leg; together, I'd run out of space to move the alternator inwards any further...... AND all the 'excess' bracing bar sticking out beyond the alternator just looked odd/ wrong.

Alternator - tight against the block

A cause of the problem (and something that Darrin from Citroen Classics made me aware of) was that the early alternators had a bigger diameter pulley than the later ones. I checked, and he was right. Of course he was!

The pulley diameter on the original Ducellier 7530A that I'm planning to use is 70mm.
The diameter of the pulley on the slightly later Ducellier 7530B alternator is 65mm.
And the pulley on the later Ducellier 7558B is only 60mm diameter!!

You could see the differences when you compared them side-by-side.

Three DS alternators, three DS pulleys

What did all that mean? Well it meant the circumference of my pulley was more than 30mm more than the smaller pulley - that's an 3cm of belt length difference right there.

Maybe I'd got the wrong belts? My belts were a matched pair (there's a DS clue right there) and were marked 'DX 231-6 D'.

That 'DX' reference is an even bigger DS clue. The parts book for my car year (manual 562) is quite confusing on the subject of belts but did list my belts - though they might be intended for US cars with air conditioning? By 1970 and catalogue 577 things are clearer. The belts I have appeared to be the standard part.

Water pump belts - parts catalogue 577 (1970)

AND 1970 cars still had a Ducellier 7530A alternator - so presumably a 70mm pulley. I couldn't see why those belts would NOT be the correct ones for my car?

Unfortunately the parts catalogues don't tell you the belt lengths.....but the belts themselves had other numbers that must relate to this.

Markings on original drive belts

The '9.5' is - I think - a reference to the width of the belt. And the '955/965' might relate to length? Not sure about the '1131'......

So. What to do? I could have cut the slot in the bracing bar to make it a bit longer, and I could have cut the leg from the base of the alternator. I could even have maybe fitted a different pulley to the alternator, but it would surely be far simpler to just leave things as they were and buy longer belts.

Been there. Done that. A few years ago I bought another set of belts from a well-know UK DS parts supplier. The belts were advertised as '10 x 975mm' and even their part reference number included '975' and '5414408'. That last number is the same as the Citroen part number for belts after February 1971.

Water pump belts - from February 1971

March 1971 saw a change in alternators, so perhaps belt sizes changed because the alternator pulley size changed? I'm not convinced about that though.

I fitted the replacement 975 belts and found........ they were just as tight as the original belts I had for my car! What I was sent was a pair of Gates 'SPZ962s'. Googling these told me they did indeed have an external length of 975mm. They had an internal length of only 942mm and a 'datum length' of 962mm. So that proved an expensive way to find the reference sizes for belts that DON'T fit my car.....

Last week I decided I would buy another pair of longer belts. I bought a pair of 1000mm length from a local motor factor. Data sheets told me the internal length - the bit that contacts the pulleys - would only be 37mm longer. Once the belt is looped around the pulleys, that extra length soon disappears, but might just be enough. But I found they were WAY too long! The alternator was right over at the other extreme of its adjustment. Compared to the '975s' from the DS parts supplier, I'd not consider that a mere extra 37mm in length would make such a difference.

I'm building up quite a collection of spare belts.