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1995-2002 Range Rover P38A
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Discussion Starter #1
For a while now... My air tank has been leaking down through the valve block vent. It's causing the compressor to short cycle. I tore the solenoid at the vent end down and checked it out. The diaphragm is in good condition with just a small permanent indentation where the diaphragm sits against it's seat. Also checked the check valves and they're looking good.

I was fiddling with it yesterday and unscrewed the little exhaust vent filter (inboard exterior on the EAS casing). I placed my finger over the hole in the block where the filter screwed in to check for air leaking by. With the compressor running there was no leak. When the compressor shuts off there is a simultaneous sharp bang of air escaping, then a slow leak, till the compressor starts again. If I hold my finger tight to the hole (when leaking) the leaking stops when I pull it away. I'm thinking there's something going on with the diaphragm solenoid as it's a "balance" type and the backpressure that I'm creating when plugging the hole is allowing it to seat properly.

During all this I got looking at the little vent filter. There's a screw in one end of it which doesn't seem to hold it together, but rather hold something internal to it in place. I can't get the little filter apart. Here's my question:

Does this little vent filter contain some gadgetry inside of it? Perhaps to provide a little back pressure to allow the solenoid to seat properly? :think:
 

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rtkraken said:
Does this little vent filter contain some gadgetry inside of it? Perhaps to provide a little back pressure to allow the solenoid to seat properly? :think:
no, the screw holds it together while the glue dries in manufacturing. I've seen several smashed apart in shipping to me, it's just the filter.

I think you're slightly mis-interpreting the function of the solenoid. It's energized when the pump runs, this ports air to the top of the diaphragm which closes off the exhaust. When the pump stops, the diaphragm solenoid de-energizes, allowing the pump circuit to de-pressurize, that way there is no pressure on the compressor piston when it starts up to minimize starting current on the wiring.

The diaphragm is open anytime the compressor is running, the diaphragm is NOT what's seating when you place your finger over the exhaust.

It sounds like the tank isolation valve (second one back from the front, on top) is leaking by, the diaphragm is doing it's job by letting this leakage out.

By this diagram -
http://www.rover-renovations.com/v/vspfiles/assets/images/diagram.jpg

shows the NRV as the only thing between the tank and the diaphragm, I think that's wrong (from an engineering standpoint, it's a BAD idea). I'll play around with it tomorrow or monday to verify, but check your tank valve.
 

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as usual Dennis has provided clarity about the EAS.

Not to hijack the thread,but A couple of questions to make it even clearer(at least to me that is :doh: ).

1) When exhausting air ,does it flow backwards thrrough the drier.(as opposed to when the pump is running.)
2) What is item 11 on the Rave diagram :think:
 

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1995-2002 Range Rover P38A
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Discussion Starter #4
OK, the bang of air makes sense now. It's got to be the NRV 1. I've opened it up and the seat and o-ring look excellent. The valve stem tip looks pretty worn, but is still retaining the o-ring snuggly.

My compressor's feeling a little under-the-weather at the moment, loose end bearing and probably worn brushes. I'll tackle that first, then t-shoot further with a strong compressor.

Having trouble finding new NRV assemblies to make the replacement?.. uh oh. /:(
 

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1-yes, that's why all the crazy air routes through the block
2- the vent for the top of the diaphragm, so it can open when the solenoid opens.

Me too, I have some a t a machine shop to be copied.
 
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