Hydraulic Pump exploration

pottsy

pottsy

Citroen Loony & BMC Nutter.
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Having created the tool mentioned in the "Special Tools" sticky, I've used it in anger to dismantle my spare 7 cylinder pump.

As expected, it's got a cracked pump body. I say "as expected" as while it worked when I tried it on Moby a couple or more years back, it was very slow and reluctant to raise enough pressure to function properly. This seemed to indicate an internal leak, and such was the case.

So now I have the dilemma.

I know I can buy a rebuilt unit from Roger Parker.

I know I can get a new pump body and seals from Der Franzose.

Both of these options appear a bit expensive, but are both achievable. Only one of these will provide me with the satisfaction of reassembling a pump and having it work as God and Citroen intended.

If I can obtain a second hand pump body then I only need to buy a set of seals as the pistons etc are all seemingly in excellent condition.

So the question is, does anyone out here have one or two pumps that may have an uncracked body that they will sell to me?

Obviously we don't know if the body is cracked until it's at least got the cover off. That's why I've said one or two to try and increase the chances of striking gold.

I await responses with bated breath.

For everyone's edification and delight Here's a photo of the bits of pump laid out and a closeup of the offending crack.

Cheers for now, Pottsy
 

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I imagine it could be done, but that's way outside my area of expertise.

I'm actually waiting for someone to tell me "that'll buff out" :)

The overall standard of machining on the piece is superb. I can't visualise being able to weld it and then restore it back to the level of finish the aluminium currently wears.

It may well be the ultimate option though.

Another possibility is to find an engineering works with a really good CNC setup. Once it was converted to a suitable file I reckon a good CNC would turn billets of ally into works of art real quick. Setting up would be a big expense though.

I'm sure there'll be plenty of options to explore.

Incidentally, has anyone ever tried adapting a CX pump to a DS? I've seen mention of BX pumps being used. Just curious.

Cheers, Pottsy
 
Ray,
Sorry I can't help, but what you are seeking is a steel body - no more cracks :wink2:

Cheers
Chris
 
pottsy said:
I imagine it could be done, but that's way outside my area of expertise.

I'm actually waiting for someone to tell me "that'll buff out" :)

The overall standard of machining on the piece is superb. I can't visualise being able to weld it and then restore it back to the level of finish the aluminium currently wears.

It may well be the ultimate option though.

Another possibility is to find an engineering works with a really good CNC setup. Once it was converted to a suitable file I reckon a good CNC would turn billets of ally into works of art real quick. Setting up would be a big expense though.

I'm sure there'll be plenty of options to explore.

Incidentally, has anyone ever tried adapting a CX pump to a DS? I've seen mention of BX pumps being used. Just curious.

Cheers, Pottsy
Click to expand...

"I'm actually waiting for someone to tell me "that'll buff out" :)"
Nope, not gonna do it, wouldn't be prudent. :whistle:

I'm guessing thats an alloy body, Pottsy? They're fairly well known for failure cracks anyway. A steel replacement is the way to go. Considering the tolerances those are machined to, welding and machining are going to be tricky.
 
Chris is right. Buy a steel body and that problem is eliminated. However, I can give you a bare aluminium body that looks fine to me. I can't see any faults in the usual places. Yours for the cost of postage. Can you send me a pm with your postal info?
 
pottsy said:
Having created the tool mentioned in the "Special Tools" sticky, I've used it in anger to dismantle my spare 7 cylinder pump.

As expected, it's got a cracked pump body. I say "as expected" as while it worked when I tried it on Moby a couple or more years back, it was very slow and reluctant to raise enough pressure to function properly. This seemed to indicate an internal leak, and such was the case.

So now I have the dilemma. I know I can buy a rebuilt unit from Roger Parker. I know I can get a new pump body and seals from Der Franzose.

Both of these options appear a bit expensive, but are both achievable. Only one of these will provide me with the satisfaction of reassembling a pump and having it work as God and Citroen intended.

I await responses with bated breath.
Click to expand...

Nice photos. My ignorant take on this is that the alloy bodies crack. I suppose that is "eventually", and only "God and Citroen" know how long that takes!

So, if a steel alternative is available, sounds like a good idea. But then, if you crave the satisfaction, which I understand completely, David's available body looks quite appealing. When it cracks you can get the satisfaction again. Two for the price of one!!

I'm in almost constant awe of Citroen devising these systems, developing working prototypes and then actually producing them in large numbers. Absolutely amazing. Yes, I know it wasn't profitable, but it was magnificent!

Cheers
 
OK, I've taken David up on his kind offer. What a wonderful bloke.

Next step is to try to source a set of O rings for the task.

I can get the set from Der Franzose but that will end up costing $155.00 roughly which seems an awful lot for a bunch of rubber bands.

Granted these seals do a grand job in difficult circumstances, but I can't help feeling I should be able to source suitable replacements here for a more reasonable outlay.

Firstly, can anyone confirm what the material most suitable for LHM is? "Ludovici sealing solutions" list theirs as being available in Nitrile 70, Nitrile 90, FKM 75, EPDM 70 and Silicone 70. I seem to recall mention of a "Buna" type as well?

My understanding is that Nitrile is the go, but I'm happy to be enlightened further by those who've already hoed this row so to speak.

I've got the list of sizes from Manual 648 so I reckon it's time to do some further research.

This is fun!

The other thing I'm wondering is where we can get the steel replacement bodies from? I know Roger Parker can supply them in his rebuilt product, and I also assume he doesn't supply them separately, I may be wrong. I suppose he may have bitten the bullet and had a batch made, more power to his pencil.

I haven't pinned down whether the ones available from Der Franzose are alloy or steel. None of the other main DS parts supliers seem to list pump bodies at all.

Inquiries will be ongoing while patience lasts! :)

Cheers for now, Pottsy
 
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From my view point the crack would be in the last stage of the pump? If it is then it is a typical swash plate failure.
Never knew Citroen made them from Aluminium, the replacement spec now would be 7075 T7(?) basically an alloy version of mild steel and anodized to retain a tough skin.

With the O-rings the correct choice is critical. Material science has come along leaps and bounds and what once cutting edge is now pretty ordinary. Buna is the older generic term for NBR (which is more technically correct) and the numbers refer to the Duro hardness, larger means harder.

Der Franzose should have to disclose the material via a Material Safety Data Advice, MSDA. If requested they shall provide, it's actually the law/requirement to sell parts into Australia to have access to this information. Aside: For a couple of years now the sale of asbestos brake/clutch and gasket materials has been banned in Australia, Has anyone questioned the E-bay seller if they are asbestos free?

Ray I hope this helps. I'm offering an educated guess from my background in hydraulics, petro-chem and stuffing around with cars. Really would like to be trained in 'Citroen' as I suspect many have paid too much for the Green liquid and it's magic.....
:cheers: Brendan.
 
FWIW here is what I have from my notes:

1ea Seal Carrier (21.3x3.6) VITON 2-212 (7/8 x 1/8) or use Metric 22x3.5
1 ea Housing Neck (27.7 x 2.7) Metric Only 27 x 3
7ea Cylinder distance piece (15.7 x 2.7) Metric 15 x 3
(Optional) 7ea Cylinder distance pieces concentric Metric 9 x 3

7ea Cylinder Bottom (18.7 x 1.9) Metric Only 19 x 2
1ea Cover (can) Seal Metric Only 90x3 (89x3 also works)
1 ea under slinger (deflector) 2-112 (1/2 x 3/32)

There are alternative O-rings if dash number are easier to source than metric.

Cheers,
John T.
 
For LHM Nitrile (Buna 70) is fine for everything except the seal carrier, which is exposed to hot air and therefore Viton will last quite a bit longer. For LHS use EPDM only.

Cheers,
John T.
 
badabec said:
Better buy the Missus a new nibbles tray for the next barbie
Click to expand...

Ssh! She doesn't know I pinched it!

Well actually it was chucked away and I recycled it as a parts tray for the workshop. In any case, a bit of LHM makes everthing taste better doesn't it? :)

Anyway, I've distilled all the information about seals into one document (herewith attached as a jpg 'cause it wouldn't let me do it as a pdf).

If anyone spots an error in it please tell me before I go chasing suppliers. I used the Parts manual, the information above and a couple of catalogues off the Interweb, but mainly one from Parco inc, for cross reference. I hope I've correctly grasped the concept of dash codes and how they relate to standard sizes, but I'm learning as we go here.

Onward and Upward Folks!

Pottsy
 

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bluey504 said:
From my view point the crack would be in the last stage of the pump? If it is then it is a typical swash plate failure.
Never knew Citroen made them from Aluminium, the replacement spec now would be 7075 T7(?) basically an alloy version of mild steel and anodized to retain a tough skin.

With the O-rings the correct choice is critical. Material science has come along leaps and bounds and what once cutting edge is now pretty ordinary. Buna is the older generic term for NBR (which is more technically correct) and the numbers refer to the Duro hardness, larger means harder.

Der Franzose should have to disclose the material via a Material Safety Data Advice, MSDA. If requested they shall provide, it's actually the law/requirement to sell parts into Australia to have access to this information. Aside: For a couple of years now the sale of asbestos brake/clutch and gasket materials has been banned in Australia, Has anyone questioned the E-bay seller if they are asbestos free?

Ray I hope this helps. I'm offering an educated guess from my background in hydraulics, petro-chem and stuffing around with cars. Really would like to be trained in 'Citroen' as I suspect many have paid too much for the Green liquid and it's magic.....
:cheers: Brendan.
Click to expand...

Interesting Brendan. Yes, the crack is at the end of the chain of interconnected chambers, the one where the fluid hangs a right hand turn and goes out into the big bad world. I'm guessing that the shock wave generated in the pressurised column of fluid at the moment of regulator cutout is felt at this point.

Is there such a thing as a shock absorber that could be added in here? I'm think along the lines of those bellows type thingies (technical term :)) you can add to your cold water tap to buffer the effect of water hammer. Of course, it'd need to withstand 2,500psi or so, but surely some kind of spring loaded expansion chamber or compensator would be available somewhere?

Maybe I'm re-inventing the wheel. Maybe I've just invented something that'll make me a fortune. Who knows?

In any case, the sudden stop of the fluid column at cutout is quite violent, so I guess it's no wonder that these things give up the fight after a while.

On the other hand, Monsieur Mages and his magicians were surely aware of that when they designed the system. I'd never presume to know more than those guys.

Cheers, Pottsy
 
pottsy said:
Interesting Brendan. Yes, the crack is at the end of the chain of interconnected chambers, the one where the fluid hangs a right hand turn and goes out into the big bad world. I'm guessing that the shock wave generated in the pressurised column of fluid at the moment of regulator cutout is felt at this point.

Is there such a thing as a shock absorber that could be added in here? I'm think along the lines of those bellows type thingies (technical term :)) you can add to your cold water tap to buffer the effect of water hammer. Of course, it'd need to withstand 2,500psi or so, but surely some kind of spring loaded expansion chamber or compensator would be available somewhere?

Maybe I'm re-inventing the wheel. Maybe I've just invented something that'll make me a fortune. Who knows?

In any case, the sudden stop of the fluid column at cutout is quite violent, so I guess it's no wonder that these things give up the fight after a while.

On the other hand, Monsieur Mages and his magicians were surely aware of that when they designed the system. I'd never presume to know more than those guys.

Cheers, Pottsy
Click to expand...

Ray,
It's my understanding that the main cause of an alloy pump failing (cracking) has to do with the continued use of a car with a flat or near flat accumulator sphere. We can't blame Monsieur Mages for that, comes down to basic poor maintenance!

Cheers
Chris
 
Chris. That's a good point, not that I would ever criticise M. Mages, he's up there with the Gods for mine.

Interestingly, Moby Dick's accumulator has always been kept above the minimum inflation, but the cycle time has always been around 10 seconds or less due to the internal leakage of the steering rack. (It's on my list! I've got a good pinion assembly, just need to build or adapt a system for setting crossover pressures and checking leakage)

It's been running like that since 2005. This is my main motivator to reco my spare so that I can strip down the unit and check it over. Since it seems to raise pressure in a reasonable time frame, despite the steering rack doing its level best to drain it almost as fast, I'm choosing to assume it's not cracked (yet) but time will tell.

Last time I checked pressures etc watching the gauge go up and down was entertaining to say the least.

And while the current pump is apparently working fine, it does seem noisy to me, so maybe the constant cycling has had an effect on the bearings too.

Once again, time will tell.

Cheers, Pottsy
 
OK so we are taking the high pressure end of the pump. The accumulator sphere does act as a pressure reservoir and a damper in the circuit, basic hydraulic unit that gets stuffed up most of the time.
Sorry Pottsy but if the cut out is violent then something is not playing with the team. The higher the regulator pressure the harder the pump has to work and the harder the cut out. It also means the fluid is getting more work applied to it and heats up and therefore is degraded faster.
:cheers: Brendan.
ps Love the DIY tools and techniques fashioned by the French car fancier.
 
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