Post by dave1800 on Jan 21, 2018 5:51:25 GMT
As many of you will be aware we are looking at the possibilities for the re-manufacture of hydrolastic displacers and hope to have an update later in the year. Sorry, no more details available at present.
In the meantime, Nick (1800heap) has been carrying out some detailed analysis of the loading of the nylon diaphragms and issues arising with the internal components.
We thought it would be helpful to provide a general guide to help owners as far as possible avoid the horrors of blown displacers.
This is not comprehensive and some of the conclusions are based on what we see as common sense and not backed up with hard scientific evidence so please bear that in mind. We welcome your thoughts and additions or changes.
1. Rubber bump stops.
Keeping the rubber bump stops in good order both front and rear is essential to limit the movement of the displacer actuating piston and prevent over extension and damage to the nylon diaphragm and over pressuring the system leading to premature hose or displacer failure.
Often these bump stops are in poor condition or missing especially at the rear. In the event of a hose blow out this will very likely cause the diaphragm to be damaged. Even if the diaphragm survives there is a reasonable chance that it will allow bits of rust to penetrate the butyl rubber diaphragm liner (seal) inside the diaphragm. At present this is not something that can be remedied.
The BMC advice of being able to drive up to 30mph on a blown displacer should be ignored and the car recovered without further movement wherever possible, especially if it is just the hose failure that can be repaired.
2. Draining and refilling the system.
Nick has suggested that when the system is drained that the rust floating in the fluid described above may pierce the butyl rubber seal. To reduce the risk the suspension arms movement should be limited to allow the rust to float free.
3. Rear displacers - dust covers
When a rear displacer is removed you may wish to try and find a dust cover as fitted to (all?) ADO16s and Australian crabs.
4. Stored displacers
These should not be allowed to dry out but filled with true hydrolastic fluid that includes the lubricant and rust inhibitor and they should be sealed.
REMEMBER: PLEASE HANG ON TO ALL OLD OR BROKEN DISPLACERS IF YOU CAN
David
In the meantime, Nick (1800heap) has been carrying out some detailed analysis of the loading of the nylon diaphragms and issues arising with the internal components.
We thought it would be helpful to provide a general guide to help owners as far as possible avoid the horrors of blown displacers.
This is not comprehensive and some of the conclusions are based on what we see as common sense and not backed up with hard scientific evidence so please bear that in mind. We welcome your thoughts and additions or changes.
1. Rubber bump stops.
Keeping the rubber bump stops in good order both front and rear is essential to limit the movement of the displacer actuating piston and prevent over extension and damage to the nylon diaphragm and over pressuring the system leading to premature hose or displacer failure.
Often these bump stops are in poor condition or missing especially at the rear. In the event of a hose blow out this will very likely cause the diaphragm to be damaged. Even if the diaphragm survives there is a reasonable chance that it will allow bits of rust to penetrate the butyl rubber diaphragm liner (seal) inside the diaphragm. At present this is not something that can be remedied.
The BMC advice of being able to drive up to 30mph on a blown displacer should be ignored and the car recovered without further movement wherever possible, especially if it is just the hose failure that can be repaired.
2. Draining and refilling the system.
Nick has suggested that when the system is drained that the rust floating in the fluid described above may pierce the butyl rubber seal. To reduce the risk the suspension arms movement should be limited to allow the rust to float free.
3. Rear displacers - dust covers
When a rear displacer is removed you may wish to try and find a dust cover as fitted to (all?) ADO16s and Australian crabs.
4. Stored displacers
These should not be allowed to dry out but filled with true hydrolastic fluid that includes the lubricant and rust inhibitor and they should be sealed.
REMEMBER: PLEASE HANG ON TO ALL OLD OR BROKEN DISPLACERS IF YOU CAN
David
