Thread: Attempt to rebuild Boge leveller.

The next problem was, I was going to have to make up a special tool to hold the top enough. I tried my super strong strap wrench that I used to remove Citroen suspension spheres ... but no go, not even close (damn it !). I was wandering around the shed trying to find something I could modify to work ... and was thinking along the lines of cutting the right sized hole out of some plate steel (somehow ) and using grub screws to lock it on...... When I spotted this
























Thinking I was wasting my time ... but what the hell. I reversed the jaws on the 4 jaw chuck... I be damned if the shocker rod didn't fit through the middle of the chuck. I woudn the jaws outwards to grab the inside of the low boot ridge....



And it moved But I have a problem... I big problem I'm not sure how to overcome. You see there is pressure behind it. I've unscrewed enough suspension spheres to know to the touch, when I'm unscrewing against hydraulic pressure ( yep, I've had the odd hydraulic fluid shower in my time ). Jokes aside, hydraulics are really dangerous, the fluid can be forced out under enough pressure to inject intself into your blood stream.



Not being really keen on wearing a heavy 4 jaw chuck, I pull it out and placed the chuck against the workbench leg, and pointed the other end out of the shed .... worse case (hopefully) it takes a joyride across the paddock. So keeping it covered with a heavy rag (so I don't get sprayed with high pressure hydraulic oil) I slowly unwound it. Not a huge amount of pressure was there... enough to blow it apart by about 30cm.



I'm going to have to understand how it works to fix it. It's not obvious by looking at it.

'Here's some photos of the thing.






See the slots cut into that housing. Much like the slide valve in a Citroen height corrector. I bet they allow pressure to either get added to the leveller or removed, dependent on the postion of the cut-outs in the bore (ie: if they match the pressure or exhaust ports in the bore, they'll allow fluid flow).



This is from inside the piston, that is actually the bore for the piston inside the housing. The white'ish ring I reckon is a seal that worn down, so the pump no longer generates enough pressure for the leveller to work.





The black thing is the diaphram/bladder the nitrogen sits behind.

I still haven't got my head around how this works, and what will need to be repaired. I'll need to have a think about this, and hit up google for explanations of how the boge works.

seeya,
Shane L

Ok, so it looks like I need to (somehow there burried) thechk the inlet and outlet valves in the pump. The rest appears to be stuff that never wears out.

All a rebuild can consist of is making sure the diaphrams hold gas (these do I released it) and ensure the pump seal and inlet/outlet valves ... well seal. Otherwise it won't pump.

So I'll need to know how much oil it needs .... if the pump works I should be able to pump any oil out of the top reseviour and onto the ground by moving the piston up and down. Then I'm guessing put the oil amount into the lower chamber, re-assemble and pump the thing to pump some of the oil up into the top chamber (reseviour). I'll just use LHM rather than shocker oil in it. It's designed for the task.

If that works, we then just need to throw some nitrogen into the two chambers (low pressure and high pressure). I'm think maybe 20bar into both Oh, or should the low pressure accumulator have less pressure so it has a higher capacity to store oil... hmmmm.

seeya,
Shane L.
PS: Images stolen from all over the net with no thought to copywrite

You know, I"ll be buggered if I can see any seals in the pump at all..... There's no seals in any of the shafts or bores. Only the double seal where the shaft exits the unit. I'm starting to wonder if correct operation doesn't rely on the unit having the correct nitrogen charge in the top and bottom reseviours

I'm still trying to figure out how they work based on the drawings - your guess would be much better than mine as you've played with this high pressure stuff before. I'll go through the diagrams and see if I can make head nor arse of it.

I could pull mine out, but I don't think I'd be confident enough to pull it apart - I have holes in my garage roof and roller door from similar things going pear shaped on me...

Originally Posted by Homestar

I'm still trying to figure out how they work based on the drawings - your guess would be much better than mine as you've played with this high pressure stuff before. I'll go through the diagrams and see if I can make head nor arse of it.

I could pull mine out, but I don't think I'd be confident enough to pull it apart - I have holes in my garage roof and roller door from similar things going pear shaped on me...

It's built like Citroen hydraulics. No seals, everything relies on oil leakage past the pistons to lubricate and prevent wear. There is one valve (pictured with the spring and nylon seat) that looks fine.

What happens with Citroen spheres in over maybe 10years the pressure will slowly bleed away through the rubber rubber diaphram ( you regass them every 2 or so years to keep them fully charged). So I'd say after for example, 10years most of the pressure has permeated through the rubber into the oil pump area (that was the pressure I was unscrewing against). I'm guessing the rebuilders are just replacing the 'O'ring where the shaft exits at the bottom, adding oil and re-charging them with nitrogen. There really isn't anything that'll wear or need rebuilding in there.

Only one way to find out I guess. I found a couple of years back a website with nitrogen pressure on it. I'm thinking 25bar but can't verify. And how much do I put in the upper accumulator that is the oil store area ? Surely not 25bar as well

25 bar is 362psi. This would give you a large amount of storage area. The accumlators on Citroens (high pressure hydraulic storage) is 62bar ( 900psi).

I'll see if I can fabricate an adapter for my sphere recharger so I can charge the boge leveller back up. We'll see

seeya,
Shane L.

the nitrogen provides the feed pressure for the pumping action of the boge.

it permeates and cross loads and also leaks away.

a properly dead one has no pressure in it as its all leaked out the priming screw or seal these usually have traces of oil leaking out of them.

ones that have died from gas transfer appear as yours did.

Very vaguely

when the vehicle is loaded up the unit compresses, this sets the unit into the lift me configuration.

the pump piston then pumps oil against the nitrogen pressure into the high pressure chamber until the valve is in the neutral position or the over extended position. The nitrogen allows for compression to occur.

when its in the neutral position all ports are sealed.

when its in the extended position it opens a trasnfer port and allows the oil to drain back into the low pressure side, same concept as opening the bleed screw on your bottle jack.

The nitrogen pressure sets the operation of it all and provides the lifting action, if you run out of nitrogen pressure all the oil winds up in HP side and eventually the valves run out of oil feed and loose the effectiveness of the oil skinning and the remaining nitrogen pressure back feeds across giving you an equal distribution of nitrogen pressure.

if you add too much oil you can run the risk of hydraulic locking the hp section. The nitrogen pressure sets the max load the leveler can support and the rate at which it will pump. lower pressure equals a lower maximum weight but a faster pumping action and higher pressure equal more weight but a slower pumping action.

forgot and my interslow is not letting me do edits properly.

the proper tool(s) for undoign the cap screw is either a cam lock spanner or chain spanner with a tensioning arm.

I usually line them with a strip of 2mm rubber or Vbelt to help prevent deforming the cap and increasing the grip friction.