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The only place for a coil spring is up Zebedee's arse
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This is a weird one.

Just switched the valve block in Sooz' car. We also refurbed the air dryer to get rid of the powder and cleaned the pipes.

Her compressor had died so we reconditioned and refitted it But it wouldn't run even when we used a jumper in the relay. We swapped in the compressor from my car and that worked fine. BUT... it never stops running, the system won't pressurise. It won't even rise from the bump stops to Access.

Since the new valve block is from eBay with an X8R kit fitted it's an unknown quantity.

We've made the classic error of changing so many things in one go we have no idea where the point of failure is. Have a Nanocom but no clue what to look for.

I've sprayed everything except the bottom air dryer collet with leak detector. Nothing. Can't feel any air leak by hand.

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Is the air from the compressor coming straight out of the exhaust port? If it is, it's the diaphragm valve leaking. Check that some air has gone into the reservoir by pulling the pipe to that one (the single one nearest the front of the car with a purple sleeve on it). Lift a solenoid coil at a time and squirt leak detect spray on the top of the visible valves to check for leakage there. You may also have bad connections in the connector between the driver pack and solenoids. I was given a valve block that had been fitted with a new kit but the O rings looked near new and the PO of the car had spent a fortune on EAS work, including a valve block rebuild. Turned out that whoever had done it previously had got the solenoid coils mixed up so it was trying to open the wrong valves. Could be that the eBay valve block has been taken apart before being sold by someone that didn't know what they were doing.

None of this explains why the compressor doesn't run though. Normal problem is an open circuit thermal switch so it won't run when commanded to by the ECU but will if you jumper the relay.

If you go into the EAS menu on the Nanocom, select Inputs and scroll across until you get to the screen that shows valve status. It will be showing front closed and rear open (as it always raises the rear first), next screens will show compressor On or Off, pressure switch status (should be Open) and Inlet valve should be Open too. Anything other than that and something very weird is happening.

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Does the dead compressor run if you put power to the green wire and ground to the black?

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Will check solenoids for leaks and placement as recommended.

To clarify the pump issues.

The one we refurbished (Pump 1) won't run at all. Orange and black show continuity so thermal cutout not an issue. Signal Pin in relay socket was getting 14.3 volts. Jumping the Fuse and Load pins did nothing until we put my good one (Pump 2) in... that ran when jumped and when we reinstated the relay. We concluded the motor in Pump 1 has burnt out.

Pump 2 just runs and runs. About 50 degrees centigrade.

Valve States as seen by Nanocom were as you describe on our final attempt. Inlet was shut but SEND TO ACCESS fixed that.

I have one of those piggy back override kits with Schrader valves arriving Friday. That should give easier pressure readings from under the bonnet.

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I will test Pump 1 with a 12v supply as suggested.

How did you figure out the solenoids were in the wrong holes?

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From the diagram on page 23 of this document https://drive.google.com/file/d/1PK5oMkoJ89oDyhTkzcw9dbcL3ObFBVfQ/view?usp=sharing

We realised something was wrong with it when the compressor had been running for a good 10 minutes, the car still hadn't done anything but on switching it off, the familiar tick, tick, tick came from the valve block as it should have been self levelling and dropping 3 corners to match the lowest one but one corner rose instead. At that point I fitted a spare, known good, valve block and I took the suspect one away to check later. After much head scratching I realised someone had been juggling with the solenoid coils and all bar two were in the wrong place. Even the two on the bottom were reversed!

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Okay, folks. It's fixed thanks to GD.

In a nutshell, some of the pipes in the block were leaking. Instead of using a weak solution of washing up liquid I bought a commercial spray which, for some reason, didn't do the job. Lots of tiny bubbles, but no big ones.

Problem located we started again. Checked if any pipes had been trimmed and chamfered, the lengths from the moulded ridge all matched. Next we began putting them back, using NEAT washing up liquid as recommended, to lube the tips.

We paid particular attention to the distance to the moulded ridge in the pipes once in. The second or third went in further than the others, so we back tracked. Eventually got them all in and matching.

If we do it again I'll mark a circle on them all with a white Chinagraph or chalk pen before removal.

GD also suggested putting a T from our emergency kit into line 6 (purple band) to the reservoir. This meant we could connect a second compressor to the Schrader valve to speed things up and take load off the built in one.

It also gave us a guage which rose to 120psi in a few minutes, then we turned it off and let the built in one finish the job.

It's an object lesson in not letting the complex parts of a problem take your eye off the basics.

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I keep an eye on all EAS threads, especially ones like this, as a way of trying to raise (pun intended!) my general level of knowledge.

On the point about marking the pipes before removal, it occurred to me that you could possibly also measure the intended depth they’re supposed to go in to, and then mark that on the pipes - if you were fitting new or amended ones for example?

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That's another way of doing it, especially if you trim the ends of the pipes. It always amuses me that RAVE, which was the official manual supplied to main dealers, suggests chamfering the ends of the pipes with a pencil sharpener and removing O rings with a crochet hook. Just what you'd expect to find in a mechanics toolbox......

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donmacn wrote:

I keep an eye on all EAS threads, especially ones like this, as a way of trying to raise (pun intended!) my general level of knowledge.

On the point about marking the pipes before removal, it occurred to me that you could possibly also measure the intended depth they’re supposed to go in to, and then mark that on the pipes - if you were fitting new or amended ones for example?

Yes. Mark the existing ones (if they are tried and tested) then measure or use as templates.

Viewed in system terms it's actually very simple. Adjustable springs, a set of sensors, a pneumatic distribution system and an ECU with 4 sets of 4 numbers to match. The diagnostics are a bit flaky "Invalid fault code" doesn't help anyone. All the electronics are 20 years old and doesn't last forever - capacitors are usually the first to go.

Mechanically it's compromised. There's no way fixed dampers can be optimised for 4 different road heights. The spring rates will vary with passengers and loads because of the leveling mechanism. The spring rates are all upside down. Soft at highway speeds and rock hard off-road. Fitting the Arnott Gen 3s partially addresses that last issue, but the rest are still in play.

All the said, I still love it, the noise it makes and the things it can do that normal cars can't. And it makes much more sense to own a car I can repair (eventually!) than open a fresh can of worms with no community of owners to help me...

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Chasman wrote:

Viewed in system terms it's actually very simple.

I've been saying that for years, it is once you get your head round how it works. I think the Invalid Fault Code may be a Nanocom thing, not sure if you get it with EASUnlock. The solenoid stuck shut faults are down to the way the fault messages have been written. It has no way of knowing if you have a leak, all it knows is it told a corner to rise, it didn't within the time it expects it to happen, so concludes the solenoid must be stuck shut. If whoever wrote the fault codes made it read 'RR Leaking' instead of 'RR solenoid stuck shut', it would be far more likely correct.

Not sure I agree with the other observations. The dampers merely damp the oscillations so are going to work the same irrespective of ride height, although I agree load will have an affect. It amuses me when people say the shocks are completely worn out as you can compress them and they stay compressed. They will, they aren't pressurised gas shocks so won't extend on their own, the test is how quickly you can compress them. As for spring rates being upside down, how do you come to that conclusion? I've always found it to be the other way round, the higher it is the softer it is. There was one road I used to use regularly where I'd turn off a nice smooth 60 mph stretch, so it would be at Motorway height, onto a pretty grim bit of potholed, bumpy, road. The bumps always felt far worse until I'd poked the inhibit and rocker to raise it up to Standard. For the same reason I always lock it in Motorway when towing (although the handbook says to lock in Standard), as it feels far more stable at that height. It's got something to do with the way the bottom of the rubber bladder wraps over on itself the lower it goes.

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I can confirm one of the points that Chasman made, because I have Arnott Gen III's fitted.
The spring rates are different compared to Dunlops. High is markedly softer, std is slightly harder and motorway height is quite a bit harder.
How is this? It is because the spring rate is dependant on the cross section of the piston, or the machined part (aluminium in the case of Arnott Gen III's) at the bottom that slides in and out of the air bag. The piston profile dictates the spring rates at various heights. Machine it different and you get a different rate. As mentioned dampers will be the same throughout the entire range, so they are a compromise.

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Gilbertd wrote:

Chasman wrote:

Viewed in system terms it's actually very simple.

The dampers merely damp the oscillations so are going to work the same irrespective of ride height, although I agree load will have an affect. It amuses me when people say the shocks are completely worn out as you can compress them and they stay compressed. They will, they aren't pressurised gas shocks so won't extend on their own, the test is how quickly you can compress them. As for spring rates being upside down, how do you come to that conclusion? I've always found it to be the other way round, the higher it is the softer it is. There was one road I used to use regularly where I'd turn off a nice smooth 60 mph stretch, so it would be at Motorway height, onto a pretty grim bit of potholed, bumpy, road. The bumps always felt far worse until I'd poked the inhibit and rocker to raise it up to Standard. For the same reason I always lock it in Motorway when towing (although the handbook says to lock in Standard), as it feels far more stable at that height. It's got something to do with the way the bottom of the rubber bladder wraps over on itself the lower it goes.

On dampers, yes they primarily damp, but the valving is tuned to a frequency which is determined by a number of factors including unsprung weight and spring stiffness. Buddy of mine does a lot of track days and bought a messed up BMW which was severely oversprung. Had to figure all that out. They were gas dampers with a rebound rate.

In our cars on stock dampers the springs do all the rebounding. That means when the springs are deflated and soft, high frequency bumps can cause "jack down" where the damper never rebounds before the next bump, moving down until you reach the bump stops. That's probably what you were feeling. The trailer thing is odd, but could simply be that it matched the height of the trailer axles.

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My train of thought, and there is no way I would ever claim to have a full understanding of it, is that the springs are never going to be soft. Irrespective of the height the car is sitting at, the weight on each spring will be the same so it is volume of air in them rather than pressure. Agreed, it needs pressure to lift the car off the bumpstops but surely, once it is at the desired height, the pressure will be the same?

To keep the twin axle trailers I regularly tow level so the loading on each axle is the same, the suspension should be in Standard, but I've found that it feels much more stable if I'm in Motorway. I recently towed a single axle boat trailer with a boat that weighs 1,100 kg so probably around 1,800-1,900 kg total and it was very noticeable that it felt far more stable in Motorway than in Standard. I've no idea why or the mechanics of it, I'm just going on the feeling through the seat of my pants. Maybe it is just that I'm lowering the centre of gravity?

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You are right, it’s the volume of air that increases to raise the car. From the point that a spring begins to lift off the stop until it hits max extension the pressure will remain the same. The pressure will increase if the weight increases. (I’m an aircraft mechanic and this is exactly how landing gear struts work).

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When towing it will feel more stable in Motorway than in Standard. In Motorway the trailer will not be level but tipped forward slightly with resulting increased weight on the tow hitch and, therefore, increased weight on the rear suspension. The pressure inside the air springs will be increased to maintain the same height with the increased weight and the air within them less compressible giving a firmer and more stable, but less ‘compliant’ ride. There may, however, be resulting effects on the trailer but these should be pretty minimal.

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It isn't often I sit and ponder why something works the way it does, I tend to concern myself with how it works and how to fix it when it doesn't, but this exchange had me intrigued so I've just been doing some sums out of interest.

Unladen weight on the rear axle with the car at kerb weight, is around a tonne (varying slightly depending on whether, petrol or diesel, manual or auto), so, as we normally measure pressure in pounds per square inch, we know the number of pounds. Without actually measuring one, I'd estimate the interior diameter of a rear air spring as around 6 inches so to convert that to square inches we multiply by Pi, giving a cross sectional area of 18.85 square inches. 1 tonne is 2204 pounds, so assuming that would be equally spread from one side to the other, meaning 1102 pounds on 18.85 square inches, or 58.4 psi.

Maximum axle weight when fully loaded is 1840 kg, or 4056 pounds, so that would give 2028 pounds on 18.85 square inches, or 107.6 psi.

In neither case is the height relevant, it won't change no matter how high or low the suspension is, the weight and cross sectional area of the air spring will still be the same. It also explains why the system pressure switch operates at 140 psi to switch off the compressor. Unless the car is grossly overloaded, there will always be sufficient pressure available to deal with the weight. This also explains why my 5.6 bar (81 psi) tyre inflation compressor was only just capable of causing my suspension to lift. Doing the sums backwards means 81 psi would be capable of holding up 1530 pounds, ample if the car was completely empty but not enough to lift it had it been fully loaded. Considering my boot carries an LPG tank in addition to a spare wheel, my toolbox, 2 tonne trolley jack, the assorted spares that live in there and it also had 3 people and one persons luggage, I suspect the rear axle weight would have been pretty close to that so right on the limit of what the pump was capable of.

What I can't get my head around is the effect the piston on the bottom of the air spring has. I know that with conventional springs when talking about spring rate we talk about deflection with weight, X pounds weight on the spring causes it to compress by Y inches, but how is that going to change? With the suspension on High, it isn't inside the rubber bit so is having no effect but when lower it is encroaching into the chamber full of air. The cross sectional area, and hence pressure, won't change though, just the volume of air needed to fill the available space will be less. So how can that influence the spring rate?

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Forget pressure for the moment and look at the dynamics of the bag itself. The spring rate just isn’t dependent on the pressure it is also dependent on the flexure of the rubber bag walls. When at High the bag has a lot of opportunity to flex outward. As the bag deflates/lowers and certainly at Motorway level where the bag is doubling over around the ‘piston’ the ability to flex becomes less and less and so the structure becomes stiffer and the effective spring rate increases.

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Now that is what I thought, the ride gets firmer the lower the height, although others seem to think it is the other way round?

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If the ride was firmer and, therefore, more ‘controlled’ at Standard height there would be no need for the lower ‘Motorway’ height at higher speeds!