Silver Shadow 1 height control - Rolls-Royce and Bentley Forums
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post #1 of 22 (permalink) Old 07-19-2015, 10:35 AM Thread Starter
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Silver Shadow 1 height control

Hi.

First of all 'hi', I'm new here. Second, thanks for any help, and sorry for the length of the post.

I'm making fair progress with the hydraulic systems on my 1969 RR Silver Shadow 1. The brakes now work, which is an improvement, so I'm trying to fix the rear height control suspension. The front doesn't work either, as it has been disabled, but that's for another day.

The situation is that the rear height control has never worked. The car seems to be resting on it's 'normal' suspension. The offside ram would bleed (opening the bleed valve sent a jet of hydraulic fluid squirting out, this would grow in intensity if someone pushed down on the back of the car, and reduce if someone lifted it) but the nearside would not. I determined there was feed to the nearside valve (loosening the appropriate pipe fitting would cause fluid to leak) but none at the ram. The actuating rod seemed to be about right. Because of this I decided to change that heigh control valve, which I have now done. Most of the pipes/hoses looked pretty grotty, so a lot of those were renewed too.

The situation now is that:

The accumulators bleed and hold pressure (the 'front' one is new). Brake pump test requires 50+ pumps to get either light on, a pressure valve connected to the feed for the front height control valve jumps to 500 when the engine is started, and climbs to 1,500 over about 20 seconds. At that point the pressure gauge unions began to leak. Switching off the engine shows the valve hold at 1,500psi, for at least a few minuites.

All brake bleed points bleed.

No suspension bleed valves admit any fluid during the normal bleeding routine, and there is no feed to the height control rams (disconnecting the pipes to the rams does not result in a boot full of hydraulic fluid)

There appears to be feed to all height control valves (again, fluid seems to be present at quite high pressure at the inlet ports)

I have tried disconnecting the control rod from the 'new' valve and actuating it manually, with the bleed open, and the engine running. Nothing happens.

I have blanked off the feed to the front and offside-rear height control rams, isolating the nearside rear.

I assume then that my solenoid valve is faulty, there being nothing else that would stop both a working, isolated, rear height control valve. Is this a safe assumption? Does a faulty solenoid valve stop the height control valve working? My next couse of action will be to test the input/output of the solenoid valve.

I would welcome any other comments/guidance though!

Thanks in advance.
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post #2 of 22 (permalink) Old 07-19-2015, 03:19 PM
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The solenoid valve does nothing besides setting fast or slow leveling speed. It could be stuck in permanent "slow" mode, but even then the car should lift itself and the rams should be able to be bled. It will just work far, far more slowly in slow mode and you generally want it to be in fast mode when you're trying to bleed the rams.

Read, Flush and Bleed Your SZ Series Hydraulics/Brakes the Easy Way, and see if that gives you any ideas.

By the way, if the car is unladen the height control should never be activated anyway. The only time it should ever come into play is if you have sufficient weight in either the back seat, the trunk/boot, or both that causes the body to be pushed down enough that the height control kicks in.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #3 of 22 (permalink) Old 07-20-2015, 08:26 AM Thread Starter
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Hi.

Thanks for the reply.

I understand what you say about the solenoid valve. I have wondered if a valve will function if I simply connect a feed, and then manually actuate it. This would make testing them very easy. It's one of those questions no one seem to know the answer to, or I've just been asking in the wrong places. This will not work with front height control valves, as they need to see a control from the roll control valve. I verfied this for myself yesterday.

With my car in it's current state, the hydraulic rams have no fluid in them, so are completly compressed. This should cause the suspension to actuate. In any case I have tried manually operating the valves and nothing happens.

Last edited by SixAndaQuater; 07-20-2015 at 08:28 AM.
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post #4 of 22 (permalink) Old 07-20-2015, 10:07 AM
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Quote:
Originally Posted by SixAndaQuater View Post
With my car in it's current state, the hydraulic rams have no fluid in them, so are completly compressed. This should cause the suspension to actuate. In any case I have tried manually operating the valves and nothing happens.
I have tried to explain to you that the system should only actuate if the car is laden or the actuator arms are manipulated to make the car think it's laden. The normal state of affairs is that the rams are completely unextended and have no reason to actuate unless the car is loaded with passengers or freight in the back.

If you have pressure going into the height control valve, and I believe you've said that you do, then the only problem can be with the action of the valve itself if the rams are not being fed fluid when you push the actuating arm upward. You also have to be careful that you do not push it too far and disengage the internals of the HCV.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #5 of 22 (permalink) Old 07-21-2015, 12:20 PM Thread Starter
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OK, thanks for that. You've kind of confirmed what I was worried about. This does point to both height control valves being faulty, including the 'new' one.

I need to systematically check both rear valves. I have already followed the workshop manual advice and isolated one. I will test it again, with a known good feed, then test the other. You make a good point about not turning the valve too far. Fortunatly I was aware of that.
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post #6 of 22 (permalink) Old 07-24-2015, 04:45 PM
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on my 69 DRX 7012 the front hight control wasn´t only disabled by removing the conection rod between the anti-roll-bar and the valve: there were small steel balls between the pipes and the hoses near the valve... nice trick to close the system.

The rear hight control wasn´t working, because the rear valve rods came a bit loose and did not move the valve... I proudly repaired the whole system including the rear rams where a seal pushed out the fluid of one brake circuit in about 2 minutes ...and when it was working again, a few miles later I deleted the whole system again (with some nice little steel balls). The reason for that is that the system is absultely useless and kind of dangerous!

The big mistake is that the system uses only one akkumulator and shares this one with the brake system!!! Though there is a restrictor valve, with a sensible attitude you can feel that the car pushes the brakes harder if you pass a for example a bridge bump while you are braking soft (I think this is the main problem why they deleted the fhc on most cars). The second problem with the restricted use of only one akku is that the main idea of the hydropneumatic is obsolete... normaly (citroen, mercedes, later cars since turbo R?) the valve pushes oil in the akku belonging to every single ram (shock absorber-style), this lifts up the car and increases the pressure in the akku... the suspension gets harder fitting to the load. On those early RR cars the ram lifts up the body and you still have the weak and wobbeling steelspring suspension but with a liftet center of gravity...

I hope my english was good enough to explain the problems of the hight control system

kind regards from the continent
Michael
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post #7 of 22 (permalink) Old 07-24-2015, 06:21 PM Thread Starter
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Hi.


Thanks for your reply and insight.


It sounds like whoever worked on your car did a better job of disabling the system than whoever did mine!
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post #8 of 22 (permalink) Old 07-24-2015, 07:48 PM
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The use of 3/16" steel ball bearings, inserted into the connection to the feed line(s) for the hydraulic component(s) you want to disable, is the most common method of doing so. This technique can also be used to temporarily take a given component "out of the loop." If the intention is a temporary isolation it is very important that one not tighten the line nut so much that you deform the flare when it's pushing the ball bearing into place.

You need to examine how the fluid distribution is handled in your car's hydraulic system to locate the best junction in which to locate your ball bearing(s).

Here are links to the color coded hydraulic/brake system diagrams for the RHD and LHD SY2 series cars from TSD4200. These are different from at least some of the SY1 series cars, but those diagrams exist in the TSD2476, the SY1 Workshop Manual, in Chapter G.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #9 of 22 (permalink) Old 07-25-2015, 08:53 AM Thread Starter
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Thanks for that.

I actually have some blanking plugs that seem to do the job, at least temporarily. They just screw onto the end of a flexi-hose. I have used them to isolate a single rear valve, the advantage for diagnostic purposes is that you can easily remove/refit them and they are visible so you remember which ones you've done(!)

Thanks for the pics. I had something similar, but not in such good quality. I'l print that out in A3, the 'zoom-in' of the rear axle would already have been helpful, and I'm sure will come in handy again.

Looking forward to getting under it again, but I need to wait until I can sort out a proper ramp again. I have a slight phobia laying under cars up on ramps/axle stands, and besides it's too dark.
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post #10 of 22 (permalink) Old 08-04-2015, 03:51 AM
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Hi, My SS is suffering from the exact problem as yours, and have pretty much done what you have done to try and find a solution without any luck, leading me to believe that the height control rams are faulty, as even the ram that bleeds does not self level when pushing down. Does your brake fluid appear frothy when bleeding the rear ram that works?
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