Top view of valve block: the view you would get from the center of the engine bay if you could see through the plastic enclosure. Five of the black solenoid valves are visible on top of the valve block. The air hose connections are on the side towards the viewer (the  temporary plastic inserts prevent dirt intrusion).
	Valve Block Side View: left or outer side (towards the air compressor). Note the solenoid valves for the 4 wheels are grouped together top and bottom, third and fourth from left on the top row and the two directly beneath them on the underside. Right hand valve in top row is the solenoid diaphragm valve.
	Valve Block Underside View: In this view you can see the pressure switch (left, with two wires attached that have been removed from the connector). The brass  pressure relief valve is to the right of it. The inlet pipe from the compressor is at top right.

Vqalve Block on Classic Range Rover. The whole assembly is located beside the chassis rail next to the air tank. Note arrangement of solenoid valves is appears identical to 4.0/4.6. Photo courtesy of Marty.

A comparison of the O-ring from Ron Beckett's rear air spring (normal O-ring) vs the leaking O-ring from the valve block.  Note the valve block O-ring is "odd" in ppearance on one side.  The other side looks like a normal O-ring.  These rings are 6mm ID and 2.5mm ring thickness.

Internal Valve Block Leaks:
It is possible for internal seals within the valve block to fail and cause strange symptoms. For example, if the seals on the individual solenoid valves for the four wheels are weak, it is possible for air to be transferred from the front to the rear springs under heavy braking. This is noticeable as a rise in the rear of the vehicle after you have stopped. Repair may be possible by replacing the individual solenoid valve seals -- if anyone has done this procedure please email me.

Other Leaks Around the Valve Block Exterior
Another air hose that can leak is the one connecting the valve block to the compressor -- this has failed twice on my 4.0 Range Rover. This hose is secured by threaded compression fittings (see compressor removal and replacement). Leaks could also occur from the diaphragm valve or the pressure switch if they become loose or do not have a good seal to the block.

Also, since the valve block consists of 3 pieces of alloy bolted together, it is possible that the bolts can loosen or the seals between the blocks can leak, releasing air to the atmosphere. Chris Romer traced an air leak (that was causing very slow pump-up of the suspension) to the join between two of the blocks in the assembly (see red mark on the photo at right by Chris Romer).

Finally, although not part of the valve block, remember the air dryer is in the air circuit between the compressor and the air tank when the compressor is running, so any leak at its connections or elsewhere would release air to the atmosphere and prevent the system reaching operating pressure.

Solenoid Valve Failure:
If one of the solenoid valves fails, it may be repairable using the official solenoid valve repair kit or diaphragm valve repair kit STC1803 available for about $70 (photo at left courtesy of Atlantic British). Dennis Altman of Rover Rennovations has used (tested) ones for about $16. Replacement of individual solenoid valve coils is covered in the shop manual and is a simple procedure.

Solenoid Diaphragm Valve Failure:
This is a small diaphragm operated by another solenoid. I have not had this fail (yet) but it is possible that failure of this valve could cause air to pass directly from the inlet from the compressor to the exhaust. Repair is easy using the same kit.

Pressure Switch Failure:
Failure of this unit could prevent the compressor from operating or even cause it to operate continuously (if this happens it is to be hoped the thermal cutout on the compressor would linit damage to it). Replacement is simple (it just screws into the valve block -- use plumbers teflon tape or some other sealant) and it is available as a separate part.

Pressure Relief Valve Failure: This is the brass item that screws into the block next to the pressure switch. Failure could prevent the system from getting up to pressure, or (less likely) if in conjunction with pressure switch failure could cause overpressure. A replacement one from Rover Renovations can just be screwed into the valve block using teflon tape or equivalent to get a good seal.

Valve Block Assembly: Removal & Replacement Procedure

I recently had occasion to remove and replace the valve block on my 4.0SE and found several items that were not clear in the official shop manual. The manual tells you to depressurize the system before messing with the valve block assembly (see depressurizing the system).  In my case pressure was already low enough not to be able to pump up the suspension, so I ignored this step (do so at your own risk).

After removing the compressor (see compressor removal and replacement), the manual also suggests removing the vacuum hose from the cruise control actuator, which I found unnecessary. However, it is necessary to remove the two screws holding the cruise control actuator to the EAS control enclosure. This gives access to one of the valve block mounting bolts -- see below. You also need to disconnect all the air lines from the valve block -- this is easily accomplished in a minute or two by pushing the collets in with a screwdriver and simply pulling the air line out (if the system is too highly pressurized, pushing the collets in might be difficult). You can unscrew the exhaust silencer at the lower rear of the side of the valve block, to gain easier access to the final air line just below it. Then unplug the electrical connectors (I usually use pliers to hold the clip open on the big one while I pull it out) and get the wiring harness out of the way, and unscrew the three bolts (8 mm wrench) that secure the valve block to the enclosure. After that the valve block and the attached driver module lift easily out of the plastic EAS control enclosure.

If you are trying to replace the driver module, this can now be removed by unscrewing the four 4 mm Allen head bolts holding it on to the side of the valve block. You also need to unplug the electrical multiplug connector underneath the valve block (C139), which is now exposed. 

If you are swapping out the entire valve block (but not the driver module), there is one complication. Unfortunately the pressure switch wires bypass the valve block connector (C139)  and go directly to the underside of the control module connector C152. One solution is to leave the connector undisturbed, unscrew the pressure switch from the old valve block and screw it into the new one (use teflon tape or other sealant). The other option is to disconnect the pressure switch's two leads from connector C152 and insert the leads from the new pressure switch into the connector. I have performed this procedure, which is simpler than it sounds, and is accomplished in a similar manner to removing and replacing the solenoid leads in connector C139 -- an operation described in detail in the shop manual under "Solenoid Coil" replacement. The only difference is that connector C152 has a very slightly different design, so that the miniature tabs that hold each connector pin in place are slightly different, but they are disengaged in the same manner. After removing the yellow cover which holds the pins in alignment inside the male connector, you bend the tiny tab back with a small screwdriver so the corresponding pin can be pulled out the rear of the connector by gently pulling on the attached lead.

Tools Required

Parts & Sources

Up until recently, Range Rover owners have had to purchase complete assemblies of EAS parts at very high prices. To remedy this situation, fellow owner Dennis Altman recently founded Rover Renovations. He diligently tracked down the OEM suppliers of all the parts and components used in the EAS system, and offers them very inexpensively to fellow enthusiasts. All the following parts are now available from him, as are reconditioned valve blocks (about $300), driver circuit modules ($200) and much else.

The following parts are for repairing the valve block -- for details see the Valve Block Rebuild page.

Valve Block without solenoids: This has a separate part number (RVH100030) but does not seem to be readily available -- Land Rover prefers to sell you the complete assembly.
Valve Block Assembly: ANR3901 (complete with solenoid valves, diaphragm valve, pressure switch and wiring harness). Rebuilt ones are now available from Rover Renovations for about $280.
Pressure Switch: ANR3902
Solenoid Repair Kit: STC2761
Diahragm Valve repair kit: STC1803
Air line repair kit (6 mm) STC8580
Exhaust Silencer: STC2762
Air hose from compressor to valve block: STC2760
Olive and nut for end repair of compressor hose: STC1472
O-Rings: See the valve block rebuild page for details and part numbers. Range Rover Owner Dennis Altman has gone to the trouble of importing complete sets of them and making them available to other owners for about $12 via his "Rover Renovations" enterprise. If you get them from him please tell him you came from Rangerovers.net!