More Hydraulic Leaks, Any Advice?

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More Hydraulic Leaks, Any Advice?

Post by David » Sun Mar 03, 2019 7:56 pm

Hi all,

Once again I have found myself with several puddles of hydraulic oil under my BX that need addressing, and the car is frankly driving me crazy now as it just doesn't seem to want to stop leaking oil; even when I think I've fixed them, another (load) start!

I thought that I'd make a start today by replacing the front struts as they were both leaking. One of the ones that I have got to be fitted was leaking oil from the top sphere mount, where it attaches to the leg itself. I thought it'd be an easy job to replace the 2 seals in it before cleaning it and fitting it to my car, however I haven't got any seals in my box to fit, I've tried to fit some slightly bigger ones, but to no avail, so simply, where can I get some? I am going to try my usual seal supplier tomorrow, but I am not holding much hope that he'll have anything suitable. This job turned into a nightmare today, especially with the rain too.

Also while I've got the struts off is there anything else worth checking as I don't want to pull them off again any time soon?

Next leak; The FDV. Again, this is pouring oil out. I have gathered that I'm going to have to pull it apart and rebuild it. I've read the rebuild guide and it doesn't seem too difficult, but will standard sized O ring seals fit or is it going to turn into another nightmare? if the latter, where can I get some?

Next, the dreaded rear suspension cylinder. I feel like banging my head against the wall with this. I have been so far unsuccessful in removing it from the car, let alone disassembling it. Has anyone got any experience of removing the rear suspension cylinders on the 4x4? The main problem that I'm having is getting the huge bolt undone. Every tool supplier that I've asked about a huge 50mm spanner have been unhelpful.

I'm also having trouble with the AC system leaking too, but that's a low priority at the moment. It's the compressor, but I'm not sure exactly where from. (and I've already put new seals in that too!)

I realise that I'm asking difficult questions here, especially when you're unable to see the car yourself, but I'm hoping that someone here has some experience to help fix even one of these leaks. Any help or advice would greatly be appreciated.
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Re: More Hydraulic Leaks, Any Advice?

Post by jamescarruthers » Sun Mar 03, 2019 8:38 pm

I'd suggest that you call Martin at Pleiades on 01487 831239. They should be able to understand what you want (for hydraulics anyway) and post seals for the strut and FDV kit (they overhaul, and set them correctly, if you want to outsource the job). If you're buying a few things, I imagine he'd happily give a minutes of advice about the rear cylinder.
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Re: More Hydraulic Leaks, Any Advice?

Post by rutter123 » Mon Mar 04, 2019 7:05 pm

Not sure you can use standard off the shelf o rings as they will prob react to the LHM, as /\ says Pleaides can supply the correct seals for the job, leaks can be a headache so getting them fixed right first time is paramount.
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Re: More Hydraulic Leaks, Any Advice?

Post by jamescarruthers » Mon Mar 04, 2019 7:33 pm

If you do use generic o-rings, just remember that LHM is a mineral oil. If you look for o-rings that will be compatible with MIL-H-5606 (or MIL-PRF-5606) you should be on to a winner
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Re: More Hydraulic Leaks, Any Advice?

Post by Jaba » Mon Mar 04, 2019 10:58 pm

Front struts: it might be worth giving them a flush out of the debris that collects at the bottom of the strut. Examine the return hoses too while you are there. Then put a bit of LHM back in the struts and store them upside down for a while to lubricate the top bearing and its felt washer as this all dries out through the years so some new lubricant is much needed.
I can't help with the rear cylinder removal on a 4x4 as I have never owned one but 50mm spanners and sockets must be available.
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Re: More Hydraulic Leaks, Any Advice?

Post by David » Wed Mar 13, 2019 6:37 pm

Thanks for all the replies about these leaks.

I have had a day off work today, so I've finally got something done.
I have been in touch with Pleiades, and they are sending me the correct seals for the suspension struts, the rear suspension cylinder & the FDV, but I'll have to wait for a day or two until they arrive.

I have also found a very helpful tool supplier that supplied me with a 50mm spanner, but it turned out that it isn't a 50mm that I needed but it's actually a 48mm. He exchanged the spanner without any trouble. (A socket wouldn't go in as there is no room, so it had to be a spanner).

I have now managed to get the oversized nut undone and removed the leaking cylinder from the car.

The actual rear cylinder looks to be almost identical to a 2WD cylinder, apart from the one off the 4x4 doesn't have the hole where the hydraulic pipe would screw in on a 2WD car & the suspension rod is shorter. The cylinders themselves are both the same length and diameter. The oversized nut on the back looks like the back of a sphere on the inside, and it has 2 hydraulic seals on either side of the union (they look like normal sphere seals).

I did let a mechanic look at the front struts last week to see if he had anything lying around that might do, but he essentially said the same thing as what you've said; about them being special seals and that they might react with LHM, so he couldn't do anything.

With regards to flushing out the front struts; where would I put the LHM into them to lubricate them? Would it be in the return hole at the bottom of the leg?

I have already removed the return pipes and I have got some good ones to put on them; the ones that were on are starting to crack. I'm just going to try to use the original metal clips and the method that's mentioned elsewhere on the forum to refit them, failing that, I'll just have to use zip ties and sealant.

Hopefully afterward I shouldn't have any more leaks, but any advice on the above mentioned points would be greatly appreciated.
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Re: More Hydraulic Leaks, Any Advice?

Post by Jaba » Wed Mar 13, 2019 8:47 pm

David wrote:
Wed Mar 13, 2019 6:37 pm

With regards to flushing out the front struts; where would I put the LHM into them to lubricate them? Would it be in the return hole at the bottom of the leg?

I have already removed the return pipes and I have got some good ones to put on them; the ones that were on are starting to crack. I'm just going to try to use the original metal clips and the method that's mentioned elsewhere on the forum to refit them, failing that, I'll just have to use zip ties and sealant.

Hopefully afterward I shouldn't have any more leaks, but any advice on the above mentioned points would be greatly appreciated.


Flushing: yes thats the place, the only way in really through the return pipe exit. I always re-use the return pipe clips by reforming them back into their intended shape then holding the return pipe in place with a removable cable tie before using pincers to close the clip up securely.
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Re: More Hydraulic Leaks, Any Advice?

Post by David » Thu Mar 14, 2019 2:58 pm

Thanks for the advice on the return pipes, I'll give it a try when I come to putting them back on.

Another quick question about the cylinder(s), (although I suspect I already know the answer here). I've just come to cleaning and disassembling it, and I have found serious corrosion on the cylinder sidewall. It looks deep, so, Is the cylinder scrap?

I have read on here that they do burst from time to time and I suspect that this will do so very soon if I refit it. It doesn't look to be leaking yet and internally it looks clean; it looks like the current leak is just the front seal where the rod goes into the unit, but I don't want to waste my time and new seals on a ticking bomb. Any thoughts?

If it is indeed scrap, then I'll have to fit the standard cylinder and block the port up where the hydraulic line would go on a 2wd car. (unless I get a hydraulic pipe made and put it between the two cylinders). Any thoughts on the effect of doing this?

I'm going to check the other side and see what that looks like, although I suspect that it'll probably be the same.

Any further advice would be appreciated.
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Re: More Hydraulic Leaks, Any Advice?

Post by Jaba » Thu Mar 14, 2019 8:39 pm

The rear cylinders are very prone to the external corrosion you have noticed. If you can see no sign of the corrosion from the inside of the cylinder then it is OK to use, probably most of them are like this anyway.
What I do is to drill a drainage hole in the underside of the cylinder mounting on the subframe to prevent a build up of water and muck which causes the pitting in the first place. Also when refitting the cylinder use plenty of waxoyl, grease or whatever around the cylinder for corrosion protection.
The cylinders on the estates have thinner walls and are therefore much more prone to failing.
If you decide to replace it dont forget that Xantia cylinders can be made to fit as well even though the pipe union boss is much larger and needs to be cut down to allow it to fit.
The disclaimer is that I dont know how much of the above info applies to the 4x4 but as the cylinders are sized identically probably it all does.
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Re: More Hydraulic Leaks, Any Advice?

Post by David » Fri Mar 15, 2019 10:42 am

Thanks for your thoughts on this.

I've still got the original 2wd cylinders that were on my car when I bought it, so I'm going to refit both of them, just using the 4x4 rods (as they are shorter). Surprisingly, the original cylinders from my car have very little corrosion on them. Both the 4x4 cylinders have deep corrosion on them, if I can, I'll upload a picture so you can see.

The information about the Xantia cylinders is great too, I didn't realize they could be used, I'll remember that should I come across this again.

I've also drilled drain holes into the cylinder mountings, so hopefully that'll help to stop it happening again. Thanks for the tip.

I was wrong about the dimensions of the actual cylinders, the cylinders are both the same length & the part that mounts to the axle are the same diameter, but the rest of the cylinder is bigger on the 4x4, & the actual piston inside is bigger too (by about 4-5mm roughly), so the seal kit that I have won't fit the 4x4 cylinders anyway. I've read that the estate cylinders are bigger, so I suspect that the 4x4 cylinders are the same as the estate cylinders, only without the hydraulic feed line (but without seeing them myself I can't confirm this).

I'm going to see what I can assemble on the car today and give an update on the progress.

I'm just hoping I can get the clips back on the front strut return pipes and it all screws together easily now.

Has anyone got any insight into what might be difficult with regards to rebuilding the FDV? (I've yet to remove it).

Any further advice would be appreciated.
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Re: More Hydraulic Leaks, Any Advice?

Post by David » Fri Mar 22, 2019 8:50 pm

Just a quick update on this thread.

The suspension is all back together on my BX, and I've yet to test it properly (and drop the car on the floor), but the worst of the leaks seem to have subsided.

I used the original 2wd cylinders on the rear and just blocked the hydraulic union up with two solid nuts. The cylinders themselves don't look to be leaking now, but it looks to be seeping LHM past one of the nuts, so I'll have to remove it again and put some more ptfe tape around it, which I hope will seal it. I wanted to put a seal in the bottom of the union and put the nut up to it, but the union is only threaded half way down, so it wouldn't work.

After I got the correct seals from Pleiades, the front hydraulic struts went together easily, so I cleaned them up and fitted them to the car, and (so far) they don't look to be leaking now, but time will tell.

I then disassembled the FDV and resealed it all using the guide in the FAQ section, however I've just looked at it now, and it looks to be leaking from the "leave me alone" screw, so it looks like I'm going to need to pull that out too. But otherwise, it looks to be dry.

Has anyone got any advice about using ptfe tape on the hydraulic unions, and of course, How do I go about removing the "leave me alone" screw from the FDV?

Any further advice would be greatly appreciated.
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Re: More Hydraulic Leaks, Any Advice?

Post by Jaba » Sun Mar 24, 2019 9:42 pm

You do not need ptfe tape ever. The sealing is all done by the rubber seals being compressed against the bulge formed in the metal pipe as the union is tightened up.

Not sure about the do not touch screw leak. If you do touch this then you will lose the calibration to give the steering the correct amount of pressure diverted to it. You could try tightening the outer ring in case this has come loose but I am not aware of seals for this as such. Alternative is to recon another FDV if you are sure it is not one of the unions leaking as they are well known for weeping, being quite difficult to seat fully sometimes when refitting.
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Re: More Hydraulic Leaks, Any Advice?

Post by Kaapelimies » Sun Mar 24, 2019 11:17 pm

David wrote:
Fri Mar 22, 2019 8:50 pm
Has anyone got any advice about using ptfe tape on the hydraulic unions


No, why? Use hydraulic sealant glue like locktite542 , they will seal even 0.5mm gaps and hold forever. And as a bonus, you can dismantle the union afterwards with normal hand tools. Leave the plumbing tape for plumbers..
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Re: More Hydraulic Leaks, Any Advice?

Post by David » Fri Mar 29, 2019 9:29 pm

Jaba wrote:
Sun Mar 24, 2019 9:42 pm
You do not need ptfe tape ever. The sealing is all done by the rubber seals being compressed against the bulge formed in the metal pipe as the union is tightened up.


Yes, on the normal pipes they do, however on the union i'm having trouble with; it doesn't have a pipe going into it, it's just a union that I need to blank off. For this I have used a nut, but it wouldn't screw to the bottom of the port, it only goes half way down, therefore I couldn't put a rubber seal in it as I wanted to do, so I resorted to putting a rubber oil 'O ring' seal on the top (between the nut and union) and PTFE tape around the threads, but I'm yet to see if this has worked.
Jaba wrote:
Sun Mar 24, 2019 9:42 pm
Not sure about the do not touch screw leak. If you do touch this then you will lose the calibration to give the steering the correct amount of pressure diverted to it. You could try tightening the outer ring in case this has come loose but I am not aware of seals for this as such. Alternative is to recon another FDV if you are sure it is not one of the unions leaking as they are well known for weeping, being quite difficult to seat fully sometimes when refitting.


I have been on the phone to pleiades again and asked for some advice about this screw. Essentially he said that it only has a ball and spring underneath it, but ideally it has to be calibrated, However he said that I could mark it and put it back in the same place and it would still work OK, But I would need it off the car and ideally in a vice to ensure it went back in the same place. Apparently the collar undoes with the screw and is used to stop the screw tightening more than required for the calibration setting. I *think* he said that it has a rubber seal on the threads of the screw just below the collar, so if I have a leak then that's what it'd be. *(He did mention a seal, but I can't remember exactly where he said that it was).

I'm not even 100% sure that it is even leaking, as the pipe that bolts over it had oil on it (which I have since found out is because I need a new hydraulic pipe, but that's another story).
Kaapelimies wrote:
Sun Mar 24, 2019 11:17 pm

No, why? Use hydraulic sealant glue like locktite542 , they will seal even 0.5mm gaps and hold forever. And as a bonus, you can dismantle the union afterwards with normal hand tools. Leave the plumbing tape for plumbers..
I didn't know that this stuff existed, I will have to look out for some, regardless of whether or not this holds. Thanks for letting me know. Where would it come from?; a car parts shop?

Thanks again for the advice.
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Re: More Hydraulic Leaks, Any Advice?

Post by xantia_v6 » Fri Mar 29, 2019 10:33 pm

If you are trying to blank off a normal female hydraulic port, you can probably use a brake bleed nipple of the appropriate size. Citroen even recommended this in some applications.