Post Number: 367
|Posted on Monday, 27 July, 2015 - 06:42 am: |
I'm working on the suspension, and the first instructions are, "Depressurize the accumulators...", which I know how to do and can verify that I have done it correctly. With the accumulators depressurized, there is no discretionary pressure anywhere, but what about "trapped" pressure in the rams? Will depressurizing the accumulators also depressurize the ride height rams or do I need to specifically address them? If depressurizing the accumulators also depressurizes the rams, then I have to surmise that it is pressure in the accumulators that keeps the rams extended, and not the ride height control valve, which is not the way I thought this worked. So, I may need a better explanation of how this works...
When adjusting the ride height, I'm expecting that I can manipulate the arms of the ride height control valve and watch the suspension react. So, obviously the accumulators need to be pressurized. If the engine is not running, can I still invoke "fast" mode by leaving the door open and gear selector in park/neutral? Does the key need to be turned at all? "Accessory" position? "Run" position? If I am stuck using the non-"Fast" mode, how long does it take for the ride height control valve to react?
I could use a confirmation that if I push the ride height control valve up, the rams will extend to compensate. If I pull the arms down, I assume the rams will retract.
When I jack the stern of the '72 in the middle at the differential, there is a substantial height difference between the port and starboard side. Measuring the distance between the tires and the ground or the point of the fender directly above the axle and the ground, I see a two inch difference between the two sides. The front, which is completely in contact with the level garage floor, shows a minimal side to side difference of a quarter inch. The car is empty of cargo, the trunk is carrying about fifty pounds of weight, and I have a quarter of a tank of fuel.
Is this normal? If it is not normal, what is causing it?
Post Number: 1555
|Posted on Monday, 27 July, 2015 - 08:42 am: |
If your height control system is actually extending your rams when the car is unladen then you have saggy springs. If there is any fluid (beyond the slight bit that's there when the rams are completely retracted) if you open the bleed screw for each respective ram the weight of the car is enough to push out what's there and retract the ram. Your understanding is correct that it's the height control valve that controls whether fluid enters or exits the rams. I really don't think of it as "pressurizing" per se, as I separate the concept of filling the space in the ram to extend it from pressurizing the accumulators, which are built with a nitrogen charge to push against.
One does not adjust the standing height at all using the height control rams. The standing height is the result of nothing but the rear springs and whatever shims are necessary to adjust it slightly. If you have saggy springs and are not yet ready to replace them you can use rubber spring spacers to adjust the standing height. This is precisely what I used on SRH33576 and the exact ones I used are documented in the RR & Bentley Parts, Repair, Restoration & Other Resources Compilation. The purpose of the height control system is to adjust the ride (not standing) height of the car when passengers and/or luggage/freight are added to the rear of the car and the weight pushes the body down (thus lowering the standing height, which is compensated for by the height control system.
I can definitely tell you that if you push the height control valve control arm upward the ram will respond by raising the car and vice versa.
I don't have a ready theory as to why your car would list in the way you describe in the rear. It's not normal.
Robert Noel Reddington
Post Number: 333
|Posted on Monday, 27 July, 2015 - 10:17 am: |
connect test bulb to the fast solenoid 2 wires. When the bulb lights the solenoid should be in fast mode.
The ignition needs to be on. Engine doesn't need to be running.
My car works in park and neutral. Doors shut or closed. Your car may be different.
All things being equal, the position of the links that work the ride valves should both be identical. So check the position of the arm relative to the spindle in the valve. The length of the link. And the position of the link in the slot. Refer to workshop manual for arm to spindle details.
To de-pressurise the rams open the ram bleed nipples under the car. The colour code for the nipples is pink.
If your car is lop sided when the rams are fully retracted. Then remove and replace rear springs.
Post Number: 369
|Posted on Tuesday, 28 July, 2015 - 12:50 am: |
Your advice about the fast solenoid is helpful, and will allow me to answer all my questions. I think with your advice I should be able to always force "fast" leveling and confirm that I have done so.
Unfortunately, the color code bands for my hydraulics have long ago disappeared, so I'm working blind, but I see the blocks with the bleed valves, so I should be able to figure it out.
Is it possible to see the rams from underneath, meaning can I visually confirm extension or retraction without the inference of body movement?
> If your car is lop sided when the rams are fully retracted.
> Then remove and replace rear springs.
Yes. Good advice. What if it is lop-sided when not sitting on the wheels because the stern is lifted with a jack?
Post Number: 370
|Posted on Tuesday, 28 July, 2015 - 01:21 am: |
This list to port that I have is really bothering me. I don't think I can blame the suspension, although the suspension is certainly not exonerated. And I don't think I can adjust the suspension until I understand what is happening.
Has anybody else experienced something like this? My first clue was when jacking at the stern, the starboard side always achieved lift-off first, which alone would probably not be unusual, but I'm thinking the inch-and-a-half or two inches difference is more then randomness would provide.
Focusing on the non-suspension aspect of this for a moment, consider the case where I have the stern raised above contact with the ground. In this case both the wheels, as measured from the lowest point to the level pavement of my garage floor, and the body as measured from the point of the body directly above the axle, display a two inch side to side differential -- well, maybe an inch and a half, but it is significant, and it is not suspension, because the same differential I see at the wheels is also apparent at the body.
I see no corresponding differential at the bow, meaning there appears to be a twist in the whole car.
This does not seem to be something that would be adjustable, but I don't see evidence of trauma that could rack a Rolls Royce, and I think it unlikely that it is a defective construction, but it is possible.
So, maybe there is a weight distribution issue? Really unlikely, because that would translate to a corresponding differential at the bow, which I don't see. If it is not weight, then what else could it be? I confess that I see a one inch side to side differential when sitting on all four wheels, which I was blaming on the suspension, and I'm still willing to blame the suspension, but it is a tougher sell. It is beginning to look like the suspension list is an artifact of something else.
Post Number: 881
|Posted on Tuesday, 28 July, 2015 - 01:41 am: |
Is the car level, as measured from the wheelarches to the ground when the car is not on the jack. If so, I wouldn't worry about it.
It may be something as simple as variable length rebound straps on your car. Maybe one is missing?
Post Number: 371
|Posted on Tuesday, 28 July, 2015 - 01:56 am: |
> Is the car level, as measured from the wheel arches
> to the ground when the car is not on the jack?
When jacked, I see a nominal two inch difference port to starboard between the bottom of the tires and the garage floor and between the body wheel arches and the garage floor. This means that the distance from, say that center of the axles, to the wheel arches is the same port and starboard. I was hoping for a side to side suspension difference, but I can't immediately find one. The list is apparent in measurements floor to the body as well as to points on the rear wheels.
When not jacked, I see a nominal one inch difference port to starboard between body wheel arches and the garage floor. I think this means that whatever is causing the list when jacked is partially mediated by sitting on a flat garage floor.
I have tried to jack the port side to establish equality of the distance from the wheel arches to the garage floor, port to starboard and I can do that. I now realize that I haven't measured to see if this translates the list to the bow. So, I will do that.
I'm pretty sure I need a working theory about the cause of this before I can undertake the suspension leveling.