Nitrogen Recharge of UZZ32 Active Suspension Shocks

August 2004

by Peter Scott

873 UZZ32 Soarers have Active suspension - oil over nitrogen cylinders. Once the nitrogen leaks away, it leaves the suspension harsh and unbalanced resulting in the dreaded 5 bounces per second. Hydraulic bouncing is common in many applications such as the nose wheel of airplanes - it occurs when the gas pressure and oil pressure become unbalanced.

Jeff Harper translated the Japanese workshop manual:

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Once the oil pressure is released the floating piston rises to the top of the bottom accumulator. It is now ready for recharging. The fronts have to be recharged to 1750 kpa (254psi)  and the rears to 1500 kpa (218psi) - common pressures for a car.

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The Citreon car has a similar setup - a nitrogen fillled ball over gas - they also have to be recharged regularly.

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The front strut gas port.

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The rear gas port. Both ports are standard M5 threaded screws.

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The gas port screws removed. These can be replaced with M5 allen screws and a special tool clamps over the gas port and injects nitrogen through the loosened threads - but with mine it was hard to seal around the gas ports without making a special tool.

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Gas port screws removed.

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My gas port screws replaced with these custom valves - a needle is inserted through the centre and the chamber pressurised. This is the rear shock - the rear steering knuckle looks to prevent charging of the shock while on the car.

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The front shock valve - doesn't hit the suspension arm.

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My four shocks back from the Shock Doctor. At last the shock are near enough factory spec - full nitrogen pressure, each one resealed with new bronze bushes and a resealed valve body and several fluid flushes.

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The isolating screw. In the bad old days I would screw this in all the way, then undo 1/4 of a turn to reduce the oil flow to the shock to stop bouncing. This allen head screw if screwed all the way in, stops oil flow in and out of the shock - needed when working of the valve body for example - stops the car hitting the ground - must be fulley out when recharging to allow the oil pressure out.

When I had my shocks recharged they were all way down on pressure. Undoing the gas ports and most of them let out a whimper of gas - not a 1500 kpa whoosh! My trouble making front drivers shock  - the one that bounced - had no gas at all!

Now the car rides much smoother - it is so much better - and the handling is terrific - no more bounce!

I think any good shock rebuilder can recharge the shocks.

In South Australia I got Walter the Shock Doctor to recharge mine:


Shock Doctor

Lot 257 Heapslip Road

McDonald Park SA 5121

08 8284 8033