Those weird old citroens

[DoubleChevron]

I've noticed we have a lot of new members here these days that have probably never really seen threads on the old Citroens. So after finding the car had lost prime and the hydraulic pump was having a fit yesterday when I moved the car I thought I'd start a thread giving a quick overview of these old cars. And why us owners find them so fascinating.

Everyone has probably seen pictures of this car all over the place. Its been featured on aussiefrogs since the forum started.

Yes it sits low and it has the "up and down" suspension. This one is getting pretty battered and needs a good clean up.... but don't worry, we'll get to it eventually. If you have an opportunity to get any old Citroen ..... Jump for it! They are just fascinating old cars .... CX, BX, GS, DS, SM .. Go For it!! You only live once.

Thy hydraulics aren't scary and are the soul of these old cars. Yes, the suspension is just "balls"... The "balls" or spheres. They are just a sphere with a rubber diaphragm in the middle. On one side of the diaphragm is nitrogen, on the other is the hydraulic fluid. So when a sphere is "blown" it diaphgram have developed a leak and allowed the nitrogen to escape. What I know has happened with this car (because of the way its acting) is the main accumulator has "blown". The is hydraulics systems storage. So normally I can hear the pump run every 15 -> 60seconds. Suddenly its cutting in and out nearly every second or so.

If we look under the front of the car .... there it is swinging in plain view ( Hmm... where is this cars undertray ?). Anyway, what you can see is the main accumulator and brake accumulator. These are both pressure storage for the brakes and suspension/steering.

First thing you need to do is release any pressure in the hydraulic system. Where the spanner is attached you open 1/2 turn to release the pressure (I don't need to as this accumulator will be dead .... no doubt).

No fancy tools required. To whip the spheres off I just use an old socket with a bit of seatbelt webbing wrapped around it.

They just unscrew easily. If the sphere stays tight once you have loosened it .... be REALLY careful, you may still have hydraulic pressure behind it.

They just unscrew quite easily. See the sphere has fluid inside it .... You should just see the middle of the diaphragm. So the diaphragm is "blown" and the sphere is full of hydraulic oil.

 

[DoubleChevron]

Normally, you just throw that sphere removed above away and fit a newie..... Me I'm a tightarse from way back.

I have a bunch of spheres sitting here .... and accumulator is just any sphere without a valve in it.

This is a valve ... so it is a suspension sphere. That valve there sets pretty much all of your suspension settings. replacing the spring and shocker of a normal car ( sort of ). So what I'm looking for is a sphere without a valve in it .... ( I'll try the parts cars around the yard too if I need to). The trick with old spheres is NOT to check there pressure. If they have been sitting on a parts car for 10+ years they may gas up and be perfectly fine. But if I put them on the pressure tester, if flat the diphragm will push up against the back of the filler plug... there is a sharp edge here .... so you rupture them by checking. Throw unknown spheres straight onto the sphere regasser.

I actaully found an accumulator is that crate of spheres. This tester is just a bunch of parts from a parts car .... and a pressure gauge I found at a junk market. So we have 44bar in the accumulator. That is more than usable. First I'll top it upto 62bar.

Years ago I purchased a regasser that requires special valves to be fitted to spheres. Being such a penny pinching pain, I built up a frame that allowed me to recharge the spheres without spending $$$ on valves.

So here is the lowdown of these spheres. Modern cars have all shapes and sizes of spheres. If there is dimples around the filler plug .... these last "forever" without loosing charge. Once they go flat, they are junk throw them in the bin. now spheres with a filler plug and no dimples around it. They go flat over times.... anything from 3years they will need a recharge. They seem to last forever so long as you don't let them get to flat. If they are allowed to get to flat, the diaphragm will hit the sharp edge on the back of the filler plug and rupture them.

So obviously given this a car owned by me I have been really crazy and retentive about keeping onto of servicing. So the reason this one failed is I last checked it Jan 13 ... Only a mere 10years ago

 

[HH1]

Yes agree, they are really rewarding.

 

[DoubleChevron]

Lets talk brakes ..... And why we all love the brakes fitted to "real" citroens .... back before poogoe took over. Most later Citroens have a brake accumulator ... or brake storage. These allow you to have brakes in the event of engine or hydraulic failure for a short length of time (enough time to stop the car several times over). Now most hydraulic citroens use a mineral oil ... So you know how you are forever replacing wheels cylinders, master cylinders, priority valves, brake lines etc.... (its never ending) on any rarely used car. Well because the hydraulic fluid is a mineral oil .... it not only doesn't take up moisture ... it protects against it! ie: your brakes last pretty much indefinitely, even if un-used.

The magic of this system is its simplicity. So we have the main hydraullic system running at over 1000psi. To apply the brakes, if there is a brake pedal in the car, it is mounted over a "button". This button is just a valve that allows the high pressure from the hydraulics into the braking system. Anyone that has never driven a Citroen before will find it most exciting the first time they stand on the brake pedal

But wait, there is more. What about regulating the force applied to the rear brakes? If we throw a couple of thousand psi at them, they will be forever locking the back wheels. How is this for absolute brilliance. Well we have hydraulic suspension remember? So what Citroen in there wisdom did was 'T' into the rear suspension circuit. Now when you open the brake valve, the front brakes use the main hydraulic system to source there pressure from.... The rear brakes use the rear suspension circuit. Stop and think about this for a minutes and the genius of it. Lets say there car is empty and there is almost no load on the rear suspension. Well there is bugger all pressure in the rear suspension, so you have next to no rear brakes (so they will NEVER lock).

Now grab your caravan and throw on the towbar, then load the rear of the wagon with bags of cement. The hydraulic pressure required to lift the cars bum off the ground is immense. Guess how much rear braking pressure you know have Yep, those rear brakes will probably be doing every bit as much braking as the fronts. Now the trailing arm suspension and the fact you are taking the pressure from the rear brakes from the rear suspenion means the car will brake dead evenly ... No nose diving. Infact I've driven CX and DS that tail dive under hard braking (how is that for keeping effective suspension control to prevent oversteer while panic braking).

Another side effect of the rear suspension supplying the rear brakes is in an outright emergency, where you have complete hydraulic failure ( I dont' quite understand how that could ever happen). But if it does, while you still have rear suspension height, you still have rear brakes, so you can still safely brake to a halt.

On cars fitted with brake accumulators (pretty much everything except ID19's). You MUST upkeep this sphere. not really for the ability to stop in emergencies.... but because they can be a danger. I've found in recent times quite a few modern cars are now using brake accumulators. They are refered on these cars as "brake bombs". You see if you let the gas level in them get so low that they will hit the back of the filler plug. The remaining charge in the sphere will be release into your brakes. In a Citroen air in the brakes doesn't require pumping the brake pedal like your life depends on it. Rather it shows as a braking delay while the air is being compressed.

So obviously while I'm here, I'm checking that accumulator. This is a simple task as I've owned this car for a long time. Which means the lines aren't over tightened and rounded ... If you can use a single hex spanner on the lines, but they shoud unscrew easily. Just a hose clamp holds this in.

Its just another accumulator once you unscrew it from the base.

There will be a seal in there, make sure it stays put .... and make sure you don't fit a 2nd seal if the previous one has stayed in place ( Don't laugh, I bet you do it too ). Lubricate the 'O'ring and fit the sphere only hand tight.

The lines have bubble flares.

There seals are simply a short length of tube. If you can't get the lines screwed in ... DO NOT USE A SPANNER AND CROSS THREAD THEM!!! ( you'll be kicking yourself if you do). Spend as much time as you can to get the line bent into the exact spot so it inserts and screws in with your fingers.

The sphere was actually ok. It was down to about 52bar. I bumped it back upto 62 just because I'd gone to the effort of whipping it off.

 

[309B6D]

Does taking off and replacing spheres let any air into the system?

Thanks for the interesting thread.

 

[DoubleChevron]

Does taking off and replacing spheres let any air into the system?

Thanks for the interesting thread.

it will self bleed except for the brake circuit (which is a dead end).

 

[pauliev]

Yes thank you, appreciate it. Reminds me of those upndown videos on youtube.

 

[DoubleChevron]

Oh man .... I think I said above .... Be careful you don't cross thread lines .... I've been working on these cars since I was 16years old. I've never struck a line that has been so difficult to just screw in ..... I spent easily an hour trying ot screw the rear line back on.

No matter what I tried .... no matter what angle the sphere was at .... I just COULDN"T screw that line in. You can either see it or touch it with two fingers. I just couldn't make sense of it. I've never struggled to screw these lines in before. In desperation I unscrewed the other two lines and pulled it back out.... removed the sphere and just tried ot screw just that line onto the base...... Nope ... AAArrrrhhhh.... What the hell is going on here.

This line leaves the regulator, follows the outside of the accumulator around .... and screws into the back of the brake accumulator housing.

OH... look at that its been pulled tight and kinked at the line support. How on earth have I done that ? It doesn't make any sense.

You see the engineering in these cars is amazing. The car is full of high pressure hydraulic, but the only rubber lines in the entire high pressure side is the front brake lines. So that line that is kinked there at the line mount has a "coil" built into it so it can

Eg: this is how the rear brake lines work without rubber in them ... brilliant right?

So this line has somehow been "pulled" on without pulling the coil out of it ( have I snared it with something line an engine crane at some point

This will be why I could screw it in, see the line is also bent/kinked over onto the pipe fitting.

my answer to this is to replace that line with one from a parts car. You don't want kinks in steel high pressure lines, if I try to bend it back it might break.

 

[gerrypro]

I did not know that your name is 'Murphy', and that the unwritten law applies!

 

[willemd]

Wonderful piece of work Shane, will be very helpful for potential buyers of Citroen's with hydraulics. I have my 1976 CX 2000 break for sale sinds October last year, lots of tyre kickers but no one serious as yet. Had a couple from Hobart but they reckon it is to expensive to buy....and in the meantime I am very reluctant to sell it. She pulls my golf cart very well!

 

[DoubleChevron]

well that was fun ... how to turn a 20minute job into 1/2days messing around ....

Now the front suspension .... Like I said before, it just the sphere ....

Its just a simple cylinder.... with a piston in it. The genius in it is its all designed to leak. It never seems to ever wear out as everything is designed to leak (there is microns clearance, and amazing technical feat for the 1950's). So the piston is a precision fit so there is just enough leakage to lubricate it so it will not wear.

This is probably the firmest hydraulic Citroen ever made in its time. and its hilariously soft compared to the poogoes here. So the center holes in the valve allows fluid flow (the bigger the hole, the more fluid can flow.... the bigger that hole the more the car will float along like its a boat on water). outside of this is discs that move when the wheel hits a bump, allowing fast transfer of fluid to absorb the impact (at least that is my feeble understanding).

These were down to about 68bar .... so perfectly fine ... but they are already off ... so why not bump them back to 75bar. This is quite exciting .... At around 78bar the Oring will often blow out in my dodgy home made regassing head .... Its a an er, "exciting" "pop" when and Oring blows out at 80bar (some 1200psi).

This is all the suspension is .... I used to think of this as frail compared to a Citroen DS ... but compared to modern poogoes it just amazing. See there is no springs ... or shockers. The is no bushes or anything in there to allow the suspension to articulate. The lower arm has its bearings encased in rubber, but that's about it. The upper arms are mounted on bearings. note the rubber boot on the suspension cylinder. Because everything is designed to leak, it then "catches" these leaks and returns them to the hydraulic tanks via a series of rubber low pressure lines.

Oh you know how poogoe fits a billion different types of brakes to there cars ( it would drive you bloody crazy). buy a citroen and say "I want Citroen CX brakes parts" .... and that is all the information you need. No VINS, no wheel sizes, so engine types, etc.... You see the fitted the save massive brakes to all cars. It doesn't matter if its a 60hp N/A 2litre diesel or a 2.5 litre petrol turbo like this car. They all have the same four piston caliper brakes up front and two piston calipers at the rear (Oh, the wagons do have bigger rear discs as they can carry a lot more load back there)... but thats it!

The Citroen DS has center point steering, apparently the CX has too (I don't understand the explanation of why though). So if you blow out a tire at any speed on these cars. The steering will not pull... the car will drive arrow straight.

 

[gerrypro]

CX steering is not centre point, it is merely, powered centering!

 

[DoubleChevron]

CX steering is not centre point, it is merely, powered centering!

That's what I thought too. Someone on aussiefrogs detailed out the reasons why it is actually centerpoint steering years ago.... I'm nowhere near smart enough to know if they were right or wrong

 

[gerrypro]

For true centre point steering the line between the top and bottom wheel pivot points must sit in the same plane as the vertical centre line of the wheel. this relationship is maintained no matter what angle the wheel is turned through. The D series the G series and the SM are examples ( not sure about A series cars -- maybe someone can confirm) The CX having outboard brakes needed some design compromises and hence Diravi became the means of achieving constant direction control under adverse situations such as a tyre failure.

 

[DoubleChevron]

Its quite amazing how simple these cars are.... You know how everyone asks me "Is that one of those cars that goes up and down ??".

Well, not really. The idea is it never goes up and down. It will always sit level. It doesn't matter if I throw 10 bags of cement in the boot, 3 giant sized mother inlaws in the back seat (well maybe that is pushing it a bit much ) .... and a caravan on the towbar ..... or am driving along with just the driver there ... and no petrol in the tank

See these manky looking bits of "stuff" under the car. They are just a slide valve, it moves one way, and pressure from the hydraulics enters the suspension and lifts the axle..... If its too high, the slide valve moves the other way, and pressure from the suspension is released back to the reservoir.

So what moves the slide valve ? A simple set of rods/linkages to the anti-rollbar. The anti-rollbar rotates as the car lifts/drops, so it will always sit at the right height. You set the height by rotating the clamp on the anti-rollbar (never touch that sucker unless the car is on ramps ... or a 4 post hoist or the car will splatter you quicker than you can blink).

 

[harrisson_citroen]

Thanks for that thread by the way. Very interesting.

 

[DoubleChevron]

the fascination with shitty old citroens just never dies

 

[David S]

... but will it run???

 

[Armidillo]

Looks like a grumpy old bullfrog, not happy about having it's rest disturbed.

 

[JohnW]

Great posts Shane. I see you showed your hydraulic clutch addition too!