Can a leaky hydraulic pump be repaired?

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dnsey
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Post by dnsey »

I seem to remember that the DS Autobooks manual had instructions for reconditioning the pump, so I suppose it must be possible for the (keen) DIYer.
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Post by geoff_h »

Andrew,

The diagram was really useful - thanks.

But now I'm really puzzled, because I can see about 0.1-0.2mm of daylight looking down on the unit (with white paper underneath for contrast) between the traingular boss component ( through which bolt 70 goes) and the main housing . I didn't worry too much before I saw the diagram since I had mistaken the traiangular flange as a mounting bracket.

I did notice though that one of bolts 70 (the one you can neasily get at) had only minimal torque on it such that I could tighten it at least hlf a turn with a small open-eneded spanner, and I am no strong-man.

Point is though, looking at the picture you would say that where I see daylight should be two closely machined mating surfaces possibly with a gasket in between. Isn't that right?

Do you think bolts are about to snap as you mentioned happened to you.

Anyone think of any normal explanation for daylight there?

BTW, the leak is definitely not coming from o-ring 5.

Also there is a meniscus of LHM in the gap i mentioned which sucks in slightly when the pump cuts in and that definitely where the LHM come out when lightly pressurized with air.

Geoff
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Post by twiggy »

Geoff.
I had xantia that had been fitted with a replacement pump 6 months earlier which started acting as you described. Brakes slow to react and then all hell breaks loose. Yes, it was the pump sucking in air through the seal. The fluid returning to the res looking like a pint of fresh pulled Guiness which is a bit of a give-away.
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Post by geoff_h »

Thanks for that, I forgot to mention, I certainly have the Guiness effect too!

Geoff
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Post by stuartb »

geoff_h wrote:
Also there is a meniscus of LHM in the gap i mentioned which sucks in slightly when the pump cuts in and that definitely where the LHM come out when lightly pressurized with air.

Geoff
Geoff,

I forgot to say in my email that my '93 Xantia VSX TD had the same symptom. It got to the point where LHM dripped from this gap unless the engine was running (when, of course, it was sucking in air instead). This was just before my attempt at bodging ^H^H^H^H^H^H^H fixing it up with Hylomar. I ended up having to fit a new pump (well, a slightly used one anyway). That sorted it out properly.


HTH,

Stuart.
1997 XM 2.0i TCT VSX Auto.
2000 Xantia HDI90 LX.
andmcit
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Post by andmcit »

geoff_h wrote:Andrew,

The diagram was really useful - thanks.

But now I'm really puzzled, because I can see about 0.1-0.2mm of daylight looking down on the unit (with white paper underneath for contrast) between the traingular boss component ( through which bolt 70 goes) and the main housing . I didn't worry too much before I saw the diagram since I had mistaken the traiangular flange as a mounting bracket.

I did notice though that one of bolts 70 (the one you can neasily get at) had only minimal torque on it such that I could tighten it at least hlf a turn with a small open-eneded spanner, and I am no strong-man.

Point is though, looking at the picture you would say that where I see daylight should be two closely machined mating surfaces possibly with a gasket in between. Isn't that right?

Do you think bolts are about to snap as you mentioned happened to you.

Anyone think of any normal explanation for daylight there?

BTW, the leak is definitely not coming from o-ring 5.

Also there is a meniscus of LHM in the gap i mentioned which sucks in slightly when the pump cuts in and that definitely where the LHM come out when lightly pressurized with air.

Geoff
For a start I wouldn't worry about the through bolts snapping - that was the result of a perfectly GOOD pump failing at it's weakest point [the bolts!] due to a 'backlog' of highly pressurised LHM that didn't have anywhere to go so the umcompressible pillar of fluid acted as a hammer blow against the pump!!

The gap you can see on your pump by the triangular flange shouldn't be an issue if that's NOT the area of leakage and 'air draw'. There's a stepped shoulder and an O ring there to take up the kind of tolerance you mention.

On my VSX I changed the regulator/accumulator and fitted a new accumulator sphere but it's still not right even after a hydraflush - likely I'll have to dismantle it all etc when the weather eventually warms up again...

Still not sure where your meniscus of LHM in the gap is in relation to the pump mind. I'll see if I can get a cross sectional drawing and/or some digital pics of my spare pump that's been partially dismantled. I'd say apart from the fiddle of refitting the cam into the 6 followers in the main pump body the whole dismatling process is no more of a hassle than breaking down a starter motor or alternator...

All the best, Andrew
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Post by geoff_h »

With Stuart's kind permission I'm posting his very helpful e-mail for completeness and for the general interest of anyone interested.

Geoff

Hi Geoff,

Always glad to help!

The flange I was referring to is the one behind the pulley (i.e. part of the mounting bracket).

I originally tried to 'fix' it by stripping down the pump and putting some instant gasket around the flange.
This seemed to work for a few weeks until, one day, I came out from work and found my car sitting in a pool of 'green blood' where the pump had given out completely.

I was lucky and managed to acquire a decent used one from someone on the forum and that fixed the problem properly.

Once the pump was replaced (and the system bled), the foaming in the reservoir went from "frothy pint of beer" to "very flat bottle of Coke" if you see what I mean.
There are always some very small air bubbles in the system, but when the system was sucking in air it had what could be described as a green, frothy scum in the top of the reservoir.


I can offer you a few of pieces of advice:

1. Do NOT attempt to repair a leak around that flange - It's no fun realising that you suddenly have no suspension, no brakes, and very stiff steering!

2. Before you condemn the pump, try to check the LHM feed pipe from the reservoir to the pump - any leaks in this pipe will cause exactly the same symptoms due to air being sucked in (but be aware that this pipe costs over £100 from Citroen).

3. I usually do my own maintenance, but if you prefer to take yours to a garage, try to find a good independent one - In my opinion they are much better than the main dealers and always cheaper. I don't know what part of the country you live in, but a post on the forum will often get other users' recommendations about garages in a given area.

I hope this helps you to get your car fixed and if you have any more questions please feel free to ask. These hydraulic Citroens can be a little bit quirky and they have their problems, but I really like them - I currently have a 2000 Xantia HDI and a 1997 XM Turbo (petrol). The old XM gives the best ride quality this side of a Rolls!

Good luck with sorting yours out.

Cheers,

Stuart
[/quote]
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Post by andmcit »

Click on the piccy to see it enlarged in all it oily gory! This is the spare two pipe pump that I've borrowed an O ring off to rebuild my single pump one!!

Image
The spare pump in bits!

If an explanation is required here goes - although I'll probably confuse matters and everyone's general understanding!! :D

The end bowl on the left bolts onto the opposite end flange face to that shown of the main pump body [right hand side] which cannot be seen. The O ring sits inside the bowl against the inner shoulder.

The main pulley [pictured centre!!] drive spindle on removal simply draws out of the main body. A collet/brass hollow cylinder is moved by the offset cam against the pistons - these can just be seen [in two layers of 3 parallel orbital rings] inside the pump and are all held in check by the collet even once the drive spindle is removed :D

Now I've totally confused myself [and no doubt anyone reading this!!] I'll sign off! :roll:

All the best,
Andrew
Last edited by andmcit on 30 Nov 2005, 08:28, edited 1 time in total.
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Post by AndersDK »

Tx for the picture Andrew -

Clearly the later type HP pump is much more DIY friendly and simple in design.
Anders (DK) - '90 BX16Image
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Post by dnsey »

Interesting thing: a while ago I took apart a pressure washer, and the pump was very similar to a H/P pump, and internally LUBRICATED WITH LHM!
It's possible that pressure washer manufacturers can supply spares which would otherwise be difficult to get.
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Post by geoff_h »

Andrew,

Thanks for the fantastic picture.

It looks then that as my leak is emerging between the triangular front flange and the main body, it is not in fact a rotary seal which is leaking.

If the rotary sel were leaking, the LHM would surely end up on the pulley face being flung all over the place. The pulley face is in fact quite dry.

Is the static seal between the flange and the body a simple o-ring?

If so, why would it fail, I wonder.

It's not under any particular pressure and not being worn by rotation.

If it is an o-ring that's gone, can a new one be got, I wonder

Any ideas?

Geoff
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Post by andmcit »

geoff_h wrote:Andrew,

Thanks for the fantastic picture.

It looks then that as my leak is emerging between the triangular front flange and the main body, it is not in fact a rotary seal which is leaking.

If the rotary sel were leaking, the LHM would surely end up on the pulley face being flung all over the place. The pulley face is in fact quite dry.

Is the static seal between the flange and the body a simple o-ring?

If so, why would it fail, I wonder.

It's not under any particular pressure and not being worn by rotation.

If it is an o-ring that's gone, can a new one be got, I wonder

Any ideas?

Geoff
Hi Geoff

I cannot see any reason why the flange should be leaking there as I don't recall there even being an O ring on the joint faces - the likelihood is ALL the through bolts may need looking at and nipping up. There is a faint possibility they have slacked off fractionally letting crud get into the joint and the whole lot may have to be removed off the engine and looked at and cleaned properly. You can even reseal the flange using a hand cut paper gasket or silicone paste etc to take out any imperfection in it's sealing.

It follows then that you're better off having a known good or at least dry tidy one from a breakers donor handy to put straight on and save on any faffing about with the old one. You'd certainly be free at your 'leisure' to sort the old removed pump out and have that as a handy spare...

All the best, Andrew
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Post by geoff_h »

Thanks to everyone for the excellent advice and information.

I hope to report back soon when I find out exactly what caused the leak.

Geoff
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Post by geoff_h »

Success!

The leak turned out to be no more than a tired o-ring.

On Andrews photo, you should just be able to see two black concentric bands about where you would expect the seal to be on the centre item in the picture.

The inner concetric band is in fact a rather squashed (with age) 40mm x 2mm (ish) o-ring.

I took the risk of dismantling over the weekend despite not having managed to get a spare pump - but lucked-out finding that I had quite a few 40mm x 2mm o-rings in my collection.

Initially fitted the softest one I had because 2mm looked a little on the thick side and I thought it would be good to have one that squashed easily.

Then woke up middle of Saturday night thinking, maybe a soft compound would take up LHM. Decided to play safe and replaced with a much more durable synthetic looking one this morning.

Did my low pressure test again - not a drop this time so looking good.

Then bled brakes all round x2 - huge quantities of air especially from the rear brakes.

All back together now and brakes have returned 100% to normal.

Interestingly, all Guiness head has completed disappeared from the reservoir which now looks like a mill pond even with the engine running. So on this evidence if anyone has froth in their reservoir, they at least some air is getting in somewhere.

For completeness sake, does anyone now the correct grade of o-ring to use? I think the one I used is probably a high grade nitrile rubber, but I know you can get them in several other materials.

(Tested the one I used by soaking half of it in LHM over night and verified no increase in size or change in appearence of elasticity compared to the dry bit. Some of the softer ones I had increased in size visibly when exposed to LHM)

Geoff
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Post by Mandrake »

geoff_h wrote:Success!

The leak turned out to be no more than a tired o-ring.
Well done! Nothing ventured, nothing gained :)
Did my low pressure test again - not a drop this time so looking good.

Then bled brakes all round x2 - huge quantities of air especially from the rear brakes.

All back together now and brakes have returned 100% to normal.

Interestingly, all Guiness head has completed disappeared from the reservoir which now looks like a mill pond even with the engine running. So on this evidence if anyone has froth in their reservoir, they at least some air is getting in somewhere.
Definately. Any frothing in the tank is a sure sign of air getting into the system, although the more common cause is a leaking pump inlet hose.

Normally the surface of the oil in the tank with the engine running should be absolutely flat and froth/bubble free.

When I replaced all the LHM in my car, for the first 3-4 minutes of running the engine with the bleed screw open it frothed just as you describe then stopped once all the air had been purged, which is normal after changing the oil and cleaning the tank, as inevitably air gets in when lifting the pump inlet hose out of the tank and/or disconnecting it.
For completeness sake, does anyone now the correct grade of o-ring to use? I think the one I used is probably a high grade nitrile rubber, but I know you can get them in several other materials.

(Tested the one I used by soaking half of it in LHM over night and verified no increase in size or change in appearence of elasticity compared to the dry bit. Some of the softer ones I had increased in size visibly when exposed to LHM)

Geoff
Not sure on that. I thought that the seals used in the LHM system were based on neoprene, but I could be wrong...

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
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