When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Anybody have any idea where the valve block vents- I have really small leak and all the struts/lines seem to be ok-thought maybe the valve block might be leaking internally, but can't seem to find the vent for valve block. It has 6 lines- 4 to struts, 1 from compressor and 1 to air tank. When car lowers from high mode to normal or from Jack Mode to normal the valve block must vent somewhere-any ideas?
The venting happens right on the compressor assembly itself, the black line I am blocking with my finger not only feeds the valve block (6 lines) from valve on the compressor, but it releases air from the valve block also, you can see the larger air intake tube into the valve mounted to the compressor, this tube has a muffler/filter, it is both the intake and exhaust for the air as I understand it, the the venting portion of the valve is on the bottom of the valve I show in my second picture, the 2 wires for the venting valve are in the brown connector plug shown in my third picture.
I would spray the entire valve block itself with soapy water to check for bubbles.
Thinking a bit more about it, I guess I could run car to get it at the jack mode setting, then remove fuse for compressor, remove the line you took off in video from compressor and see if I'm getting are leakage at that port. Does this make sense?
Thanks for the reply! At first I just figured that 4 lines went to the struts/shocks and 1 was compressor feed and 1 was the vent, but tracing it down and looking at some service manual diagrams it was clear the 6th line went to the reservoir in the LH rear fenderwell and was not a vent, so then I thought maybe the valve block just had a small weep hole to vent when you lower the car from either the jack mode or the high setting, so I soaped the whole thing but could not get any bubbles. I had found leaks on one of the front struts previously, so based on this being somewhat common, I replaced the struts with struts from Meissler in Germany(Super impressed with them-not only the quality but the function is great also and $1700 for pair including shipping/tariff and no core needed!) this slowed the leak down quite a bit. It went from all 4 corners leaking down overnight to just the right front after a couple nights. Even tho strut was new I soaped down the strut and air connection and zero leaks, so that led me back to valve block. According to the Indy I have used the valve block causing leak down is quite common on Audi A8s, so I went looking. It must be leaking internally and venting back to compressor-but not sure how one could prove it easily, so I think I'll just replace it with one from Alpine Performance and see if that resolves it. Previously to any repairs I also noticed that if I raise and lower the suspension between high and normal a bunch of times while driving, the time it took to leakdown would be 3 or 4 days vs overnight, so now I'm thinking that cycling the valve block a bunch of times maybe loosens up some corrosion and it seals a bit better for a short time. Do you have any thoughts to add to this??
Would love to put this to rest before I dive into the big service, spark plugs, cam cover seals, EGT circuit boards, Brake fluid flush, coolant flush, trans service, and diff and transfer case service. I already did a power steering flush and service. At that point I would have all the services up to snuff and then can maintain per schedule from here on out. Car had regular services, but have not done the above items as far as I can find. At 15 years and 40k miles it's time. ***********(For some reason this did not post before my other reply)********
@09Speed ,
Put the vehicle suspension into the highest height setting, then put it in jack mode, as jack mode kills all power to suspension compressor, and sensors, as the suspension control module is locking all functions out, therefore no need to pull any fuse, then, being that you say it is the right front strut lowering over time, you need to spray the top of the strut under the hood, along with the very bottom of the strut accordion cover, not just the air line and upper body of the strut in the wheel well, as brand new strut have been known to leak at the top were the wires come out, that would be my first inspection, as you say you sprayed the valve block, so I assume no leaks at the valve block on the green line.
Johnny, the whole car will eventually settle, but the right front settles quicker than other corners- to me this has to mean that there is an internal seal problem in valve block that is venting thru the compressor intake/exhaust to allow the various corners to leak down over time. Per the Indy I have used, this is what he says they see on Audi A8s. I don't know if the A8s are plumbed exactly the same, but I think from how he describes and the fact that they use the same parts, my guess is they are and in the Audi's case the valve block replacement solves the problem, If there is no physical explanation of how a single leaking strut causes the whole car or portions of the car to settle over time when no other strut, line, or external leaks are found beyond a single leaking strut, then the answer can only be internal leaking in valve block. thus if your car is leaking at a given strut but other corners also drop but no leaks are found on strut or associated piping of that strut, then a valve block replacement should be done along with the strut pair where leak is found. Does anyone have a different explanation? I keep mentioning A8s because they see those much, much more A8s than Bentleys in Michigan, especially the west side of the state.
Johnny, I did not have in Jack Mode when checking for leaks on struts or valve block, do you think that matters? I found the leak on LF strut without jack mode altho that leak was coming out around the bag clamp area, not the top of strut. Putting it in Jack Mode and then removing the air compressor line at valve block and checking that port for air leaking should prove whether valve block has internal leaks or not, right?
Johnny, also thanks for your very informative and detailed posts, you are a treasure for this board and a great resource for the Bentley owner. Thank You!!!
@09Speed ,
I understand about the comparison to the A8L, I have one of those also, an A8L W12, with over 200k miles, all on original struts, compressor, and valve block, same as my GT, all original struts, so I always wonder, what in the hell is wrong with all these Bentleys having suspension failures...
Now, on to the reason with only one strut leaking causing the entire vehicle to lower, the A8 usually would have all four corners fall, whereas many here would only have both fronts fall, yet leaving the GT rear end up as normal, and here is why, depending on the Audi vs Bentley model, and from all I have seen from many on here and Audiworld, this is the issue, you can have your front right strut slowly leaking, therefore overnight the vehicle tries to keep itself level, but, being that the engine isn't running, and voltage begins to drop from the compressor running, the system gets wacky, as it is trying to fill the front right strut, but instead of the valve block only opening the one piston valve for said strut, as in an individual corner, it opens each strut piston valve on the valve block for each axle, meaning front and rear, so when it can not fill the one side, it pulls the other side down, this issue becomes worse as to when the vehicle is being allowed to operate for a period of time that causes damage to the compressor itself, therefore the compressor fails to output the proper psi.
If you have the Ross-Tech VCDS, I would do the output test on the suspension and see that you have 16+ BAR output, and the reservoir BAR reading.
Many have wasted replacement of the valve block, suspension control module, level sensors, etc, when it was a long leaking strut that wore the compressor to the point of only an output of 6 BAR, if that, so a scan and a output test is required to determine a healthy compressor, especially since you have already sprayed the valve block for leaks.
Johnny, I understand what you are saying, but like in my case I keep it plugged into my CTek 7002 charger every night. I have run a VCDS auto scan on my car quite a few times and even before and after strut replacement I have never had a code for for anything air suspension related. I have not done any output tests, just recalibrated the heights after readjusting the level sensor links to get back to normal ride height-PO had lowered the car with adjustable links. I will check the out put and see what I come up with. But if my battery is always topped off wouldn't the compressor run to keep at ride height or doesn't the compressor run when all the time when car is off, mine only seems to come on when I have fob in my pocket and am close to car, or if I open a door or the trunk, then I might hear it come on. The other day, I had fob in pocket and was working on another car of mine next to Bentley and I heard the compressor run about every 45 minutes about 3 times(ran for maybe 20-30 secs max), then I didn't hear it run at all for the next 3-4 hours, so it doesn't seem that it consistently runs, maybe there is something in the software or control system that shuts the compressor down if its run over so many times in a certain amount of time to protect the compressor and keep car from going dead??
I think possibly the fact that A8s are much more likely to be daily drivers, thus the high mileage on A8s vs Bentleys that are much more low mileage weekend, not daily use could explain why one has strut problems, my guess is sitting static is not friendly to an air suspension. See the same thing in RV world with big diesel pushers, fulltimers who use there coaches regularly rarely have bag or suspension issues, but the ones you hear about are coaches that sit a lot.
@09Speed ,
OK, that is not normal for your compressor to run every 45 minutes 3 times in a row, that's a definite leak, and yes, as I showed in my video, the compressor has a temperature sensor mounted by the head of the compressor, if it runs to often or for long periods, the suspension control module will shut the system down until the next restart of the engine.
So let's see what your compressor output test comes up with, also, as I suggested, I would check the very top of the front right strut as I pictured with the bubbles.
Johnny
Last edited by Johnny Hotspur GT; Nov 13, 2025 at 09:17 PM.
Ok, that makes sense, just seems like compressor wouldn't get too hot running for 20 secs and then off for 45, but maybe it's a number of times it runs vs heat alone.
We did check the top of the RH strut- sprayed everything on right hand strut after replacement. What's weird is it's never consistent, the more I drive it the less it drops over night, but even with that sometimes it will go 2-3 days and hardly drop and then sometimes it will drop a lot in one night. For an example, I might move it from one bay in my garage to another one so I can get another car on hoist and then it might drop a lot that night, but if I drive it a fair amount for 2-3 days in a row, it might hardly drop at all overnight. If it was more consistent, I would think a strut issue, but the other seems like valve block sticking. Where does the intake/muffler terminate? maybe I'll stick a balloon on it and see if it blows up over night, LOL
My sciatic is currently very angry with me about taking care of all these fall leaves-I live in woods- so it might be till next week as I'm on time out with Mrs Speed for a bit
"Yes, there is a Lift Mode, and a Jack Mode, but the "lift mode" has nothing to do with a lift, such as putting your vehicle on a lift in the shop, lift mode is putting the vehicle in it's highest height position, it therefore lifts the vehicle at all four corners for ground clearance, we put it in lift mode, then jack mode, and let it sit on the ground overnight, or a few days, the corner that drops first is then where you would start your diagnosis."
Given that the system is basically shutoff in this mode, it would seem to be a good way to isolate which corner or corners have a problem, assuming the valve block is good as all valves would be closed. If you've checked a strut for leaks and it goes down in jack mode, that would seem to indicate a valve block issue. Does that make sense to you?
On VCDS is there a way to do output test on just compressor? I only see a test for whole system, it raises and lowers each corner, but does this all off of accumulator so compressor doesn't run- saw 6.84 and 10.82 the couple times I ran it. Maybe just keep running it? I get a system fault when trying to put in jack mode, but never get a CEL, when I run an auto scan, level control always shows zero codes or issues. Only thing it shows when system fault comes on dash screen is "switch is off". Any ideas?
