i have a 2001 4.6, iv noticed that sometimes when i get park up and get out there is a (HISSING)noise that seems to be comming from underneth?? i dont now if its the norm or not? its happened only a couple of times and on the exit setting of the suspension. may be this is normal but iv never had a range before so if i dont ask i will not know..

i wouldnt of thought a hissing is normal, its sounds slike a leak to me! stranger it should happen on "exit" setting as you call it as there's normally no pressure in the system when it drops that low!!, i think?

its only happened twice but both times it was on the low setting(suspension) It all work fine(i think) go's up and down to all ride heights with no probs, say 5-10 seconds from one height to another..

Maybe youv'e run over a snake!

There is still some pressure left in the air springs when they are at access mode.

If you get out and leave the vehicle in standard profile do you hear the hissing then?? Does any corner drop over a couple of hours or anything??

With the vehicle in high (the top light on the height selector) mode, open the drivers door and then the tailgate. Now, get underneath the vehicle, preferably where you heard the hissing from and look at the air springs. What you are looking for is cracking/crazing/splitting of the rubber, bit like the pictures below...




This was one of my front springs when it got replaced, the cracking isnt that bad but the split on the bottom photo would open up at the high height and leak air and you could hear it hiss.

So, even if you dont hear hissing in high mode but your springs look perished on the outside like the one above then you may have a small split that only opens up at a certain point such as when you are in access mode.

To try and confirm this, borrow the other halfs plant sprayer squeezy bottle thing and fill it with soapy water (more soap than water, you want bubbles), get underneath with the vehicle in high mode and spray the soapy water directly onto the springs, you are looking for bubbling to indicate air leaking. If you cant see any, lower the vehicle to the next level down (DONT LOWER WITH ANYONE UNDER THE VEHICLE AND MAKE SURE TO OPEN A DOOR AND THE TAILGATE WHEN AT EACH LEVEL TO PREVENT SELF LEVELING) and repeat the procedure, continue until you are spraying the springs with the vehicle in access mode. Im guessing you will find a leak somewhere.

Post back with any results and we can go from there.

-Wills

It's normal for the car to self level when you get out, it may be this you are hearing, personally I wouldn't worry if all else is working

thanks wills ..i am at the garage on wed. so will put it on the ramp and have a look.its done it again today seems to be comming from the rear pass side. the car drops over night a little but rises straight away when you kick it over..will be back with outcome thursday??

had her checked over today and all seems well looks very clean underneth checked out suspension springs (thanks for your pics wills realy helped)all look new or at least as new no air leaks garage couldnt find anything wrong,but she dose drop at night..they said if she go's up and down as quick as she did for them ,then to leave well alone.still wonder why she drops evey night ???

As with any system using compressed air, there is a loss of pressure when the source (Compressor) is turned off due to very slight seepage past valves, joints etc. I would think that to design & make a 100% air tight system would be highly expensive and at the end of the day there is a "Live" compressor to top the system up. I appreciate that tyres stay inflated at the set pressure for a long time but the bead design is different and there is only the valve in the system. For your system to operate the way it is-don't worry. Is there any P38 owner out there who never varies the height and never has the compressor fire up first thing in the morning if only for a few secs.-I doubt it

just happy someone how knows what to look for as checked it over(not up on tech stuff yet.. may never be.).

Is the exhaust silencer fitted to the l.h. side of the EAS box (Behind the bunch of 6mm nylon pipes coming out of the side of the box)??

irishrover you well and truley lost me with that one.iam not very tech (but i am tring)...

rob evans said:

had her checked over today and all seems well looks very clean underneth checked out suspension springs (thanks for your pics wills realy helped)all look new or at least as new no air leaks garage couldnt find anything wrong,but she dose drop at night..they said if she go's up and down as quick as she did for them ,then to leave well alone.still wonder why she drops evey night ???

Click to expand...

She will drop for one reason, possibly two. First reason is because you may not have parked the vehicle on perfectly flat and level ground, this can mean the EAS ECU will try and self-level. Basically, when you get out the vehicle and lock up the EAS ECU looks at the height sensors to make sure all is level. If it isnt then it will lower to the corner that is the lowest to try and achieve a level. However, if you are on uneven ground this wont work as once its re-leveled the EAS ECU will still see an uneven-ness and as such starts the process all over again and can get itself all the way down. Once its happy with its level it will stop but every 6 hours it rechecks the height so if you come home at 10pm and lock up, in 6 hours time, 4am, it will level again.

Ive parked in some places on uneven ground, got out and quite literally watched my P38 drop to the bump stops as it tries to level. When its leveling you will hear it doing so as the valve block will have audible clicks coming from it, each click will be accompanied by one of the corners dropping a bit.

Next reason is air temp. Basically all the air springs are are rubber bags filled with air and as such they are affected by air temperature. On a hot day you might find if you have left the vehicle for any amount of time the air in the springs has heated up and made the vehicle rise a little, its goes the opposite way when its cold.

Lastly, like Irishrover said, check the exhaust valve is present and correct, I cant see any reason why it shouldnt be unless someone re-built the valve block and didnt put it back on. In true Blue Peter fashion, here is one I made earlier, lol...



The exhaust silencer is shown in this photo. I think you only way you are going to know if its present is to use a mirror to look as this is part is actually on the bottom of the EAS valve block. So the photo you see is of the underside of the block with the air line holes shown as on top.

-Wills

Sorry Wills-you got it wrong. The silencer is at the top l.h. of your picture to the left of the outlets with the dirty white band on it.

Must add great picture though!!!!

whoops, yes, your right Irish, my mistake! was doing a million other things at once and didnt even think about what I was doing.

Although, just looking in Mircrocat, that drawing in there for the air exhaust silencer looks very much like the pressure relief valve which i highlighted instead of the actual silencer.

So yes, sorry, exhaust silencer is the thing on the top left, not what i circled, will concentrate more on what im doing from now on.

-Wills

Sounds like you have an air spring leaking

yes you would think so.. but i have had them all checked out and are all in perfect order??