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Discussion Starter #1
I have tried posting on several Porsche web pages to no avail. Appreciate it if anyone can help.

I have a 2006 Cayenne Turbo S with air suspension.

The rear of the car is going down over night by approx 85mm, the fronts are at normal height.
If I unlock the car, (without getting in) the accumulator discharges air and pumps it back to normal ride height. There are no fault lights on on the dash.\
If I put the car in Jacking mode the results are the same.

I have sprayed the soapy water on the rear air springs and there is nothing obvious, I think i need to take them off and dip them into a bowl of water or something.

Are the two air shocks connected together somewhere if so where, I think there is a leak and the other shock is leaking into it. Is there a T piece somewhere or do the air connections both go back to the block on the right hand side....

I am happy to test or remove anything but need some guidance.

Please help
 

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The leak is after the distribution block located at the compressor. So the places to check are the air line back to each shock (which very rarely leaks), the RPV (residual pressure valve) which is at the top of each shock, and lastly the shock itself.

After the air line, the least likely part is the air shock. They do leak some, but it is about a 20% chance it is the spring.

The RPV are a known problem. They stick shut and cause the "rear end won't go down problem. They also often leak, where they are screwed into the top of the air shock. 80% chance the leak is here.

The leak can be really slow. Sometimes it is hard to find with soap bubbles. Get the bubble soap solution from the kid section of a store. Coat the area with the sticky soap. Start the vehicle. Let the rear rise. It can take 15 minutes to sometimes see the leak.


aerosus.com/vw/touareg/vw-touareg-residual-pressure-holding-valve-rear


clubtouareg.com/forums/f44/how-to-replace-a-residual-pressure-valve
 

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"If I put the car in Jacking mode the results are the same."

The results are the same as what??? Does the rear still go down overnight? Please be more specific. Thanks!

X2 on checking for leaks with soapy water. spray the solenoid valve block, too. remove the plastic cover where the compressor is. The valve block is the device where all the hoses enter into.
 

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Discussion Starter #5
OK thanks for the replies, here are some of my replies :-

1) When you start the car, does the suspension on rear go up or does it still stay low?
When i unlock the car the suspension raises to normal on the rear, the front does not move as it is at the correct ride height. When i start the car the compressor runs, i assume to recharge the accumulator then it goes off approx 60secs of run time.

2) "If I put the car in Jacking mode the results are the same."

The results are the same as what??? Does the rear still go down overnight? Please be more specific. Thanks!

.......So the vehicle is losing height at the back overnight by approx 85mm, the suspension is in normal setting and normal ride height. If i put the car in jack mode and lock the car and walk away and leave it 24hrs, the car lowers on the rear by the same amount ie 85mm. when i unlock the car the accumulator discharges and raises is back to normal level, if i start the car the compressor kicks in and recharges the accumulator. putting the car in this mode makes no difference to the end result.


Just one other point, 600 miles ago the car went into Porsche to have the PRV replaced as the rear was stuck high. They replaced both PRV's on both rear shocks. As this was such a simple job I did not think that they could get this wrong, ON BOTH SHOCKS ??

The schematic in the manual shows that the shocks are joined together via a Tee Piece then they go back to the distribution block, is this true ? by what you say they both have their individual air lines going back to the distribution block. If this is true why are both shocks sagging, surely one would stay up and the other down if there was a leak in one of them. Does anyone have a schematic / drawing.

Thanks again, comments please.
 

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Discussion Starter #6
Sorry I meant RPV's .....

Could I take the shock off and check the RPV's and put some compressed air in it somehow, jubilee clip some pipe over the RPV and use a regulated compressor to but a few PSI in it and then check for bubbles ?....check it on the bench.
 

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Discussion Starter #8
OK I have found the leak and it is on the same point both sides. The LHS is leaking but not as bad as the RHS.

Basically, the valve is NOT leaking, it is above the valve where the top of the shock mount saddle (item no 5) meets the air spring (item no 7) . I can see that there is a large diameter O ring inside (item no 5) , I am guessing that if I replace that the issue is fixed ? or could be.

Anyone know if I can buy this separate or is it a full rebuild

Thanks
 

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If it is the pipe itself at the end, then you can just trim the 5mm or so and reinsert it into the shock. Common fault
 

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Discussion Starter #10
When you start the car, does the suspension on rear go up or does it still stay low?
If it is the pipe itself at the end, then you can just trim the 5mm or so and reinsert it into the shock. Common fault
No it is not the pipe, it is as per my explanation at the top...photos attached
 

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Nice that you posted pictures. Thanks.

I don't have the specs for the o-rings internal to the shock, but we have reports of owners who replaced them.

They are an available standard size o-ring. Once you track down what size they are, you will be able to get replacements. Since it is listed as part number 5, it might be just as easy to get them from the dealer or online from ECS tuning.

Most towns have a local industrial supplier of basics such as hoses, o-rings, bearings. You could track down one of them and take in the used o-ring to be matched. If you get really lucky, you might find one over the weekend at a hardware store or auto parts store.
 

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Discussion Starter #17
Another quick question :-

Now the air spring has been removed from the car and the top has been removed from the air spring via the x4 bolts, all the air has leaked out of the spring as expected.

Can I just replace the O ring and reassemble then bolt it back onto the vehicle and let the compressor on the car do the rest or do I need to take it to the dealer (off the car) so that he can part fill the air spring such that it holds a residual pressure.

The reason I ask, is because when I removed the air shock from the car completely and then unbolted the top mount there was quite a bit of pressure still in the shock which was released when the top mount was undone.

Thanks
 

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At the factory, the shocks are filled with air. The residual pressure valve (RPV) will hold air in the shock, as you have found. The lines to the compressor are then connected.

You can fill the empty shock with the on board compressor. Just take care that you don't let it run too long. I would turn the ignition key on for a max of 2 minutes. Then turn the key off for 5 minutes. Then back on for 2 minutes.

It will probably take a while to fill it this way, but the wait is better then overheating the on-board compressor.

Just to clarify. The last time I needed to run the compressor, it was necessary to turn the key to the on position, ie: the dash was active. This will quickly run down the battery so you might need to be connected to a battery charger.
 

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Discussion Starter #19
OK thanks for this it's good to know. In that case if I had the correct screw in fitting for the brass valve on the top of the air spring could I part fill it with my compressor in the garage if I set it to say 4 bar. The reason I ask is because I made a homemade tool to fit to the compressor with a gauge and ball valve and screwed it it the top of the air spring via the pressure valve and tried to put 1 bar of pressure in it so I could dip the shock in a bath of water to leak check it but I was unable to charge the shock to anything even with 2 bar. Both valves are new and working.
 

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Look for the tool T10157/1 which is a fill tool used for the initial filling for the air shock.

VW Snap-On Tool Link

T10171/1 USED FOR INITIALLY CHARGING A NEW AIR SPRING STRUT BEFORE INSTALLATION ON VW TOUAREG AND AUDI Q7 VEHICLES.
 
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