Rear bags settling overnight - evenly... Weird. Looking for ideas (1 Viewer)

[Makakio]

Hi All - first off thanks for the read and ideas as I don't have a schematic for the rear air on my 07 470.

Have owned it since new. Put the 5100s on her (lift 1.5" front) and tricked the bags in the rear with washers to get her even over a year and 15k miles ago (now at 175k total).

This is an intermittent problem: some nights she settles. Most nights she does not. And she settles evenly. So, not just a story of a/one bad bag. She's a California car and has zero rust. Everything is mounted up tight. What I *have* noticed, is that if she blows off some air and settles after parking (say four people get out), she's more likely to be flat on her bump stops in the morning. Then she pumps up for the day and all is fine.

I have bags and want to keep them because I tow and we travel and my girls pack HEAVY. And she holds air just fine when towing or loaded heavy - overnight even. So I cannot understand why some nights she loses all air (and always when unloaded).

I *suspect* it's the valve that blows off the air upstream of both bags (perhaps not closing completely when under average load?). But where is that valve? At the pump? Is the pump a nightmare to get to? I assume I can find a good working one here from someone ditching the system for coils - but before just throwing parts at it can someone educate me or throw some technical opinion in my direction?

Kind thanks.

 

[Rednexus]

I had the same problem. Both bags were dry rotted and had micro cracks. Sometimes it would sink, sometimes it wouldn't. If you put the GX on the high setting you should be able to visually inspect the bags for cracking. The cracks are less noticeable when the bags are on the normal setting.

 

[thabruiser]

Correct me if I'm wrong but even one bad bag can cause both sides to deflate over time, as they are both tied together at the pump, are they not? I have replaced or removed several sets on customer's vehicles, but I never paid attention if they were pumped individually or not. I'd say you have a bad bag.

 

[Jstawgn]

The airbag are like tires. Should be replaced every 10 years if you want reliable performance.

The system are separated left and right. It have separate sensor and solenoid valve for each side.

 

[redeyeracing]

What everyone said above. Mine would go flat in 2 days when I picked up mine. My bags looked fine, until I took them off...where the folds in the bag had pin holes were slowly leaking. I did aftermarket bags and Luftmeister shocks and love it. Will build my expo vehicle after I'm done with it as my smooth traveler vehicle.

 

[Makakio]

Thanks for the feedback all - appreciated. If you have the time, please keep with the ideas as I'm noticing some conflicting info here that confuses me:

There's a reply stating a tear/hole in one bag will deflate both, but then why is the most-common sign of a bad bag one falling corner? And wouldn't one be able to replicate the leak situation? This is intermittent and happens when unloaded, riding at normal height. FWIW - at full height I'm seeing no cracks, rot or leaks.

There's a different reply saying the bags are independent systems with their own lines (and I cannot find a mechanical diagram of the system to save my life), so this would point to an upstream issue.

At this point I think the second scenario is more likely, but any idea if it could be a ride height sensor failure (is that mechanical or electronic)? Or a solenoid or valve at (or just after) the pump, upstream of the line split?

 

[rommelrommel]

The bags each have a line out of the air system and they both have a sensor, I do believe that they are independent.

HEIGHT CONTROL (AUTO-LEVELER). 2008 Lexus GX 470 | Lexus Parts & Accessories Online

2008 Lexus GX 470 HEIGHT CONTROL (AUTO-LEVELER)

parts.lexus.com

I think people have experienced both leaking because time should effect them about equally, by the time they're leaking badly I think both will usually be.

Despite it being a bit odd to be intermittent I would replace the bags first before you worry about other parts, at 15ish years old they're shot or about to be shot.

I really recommend the Arnott bags from rock auto or elsewhere, do not buy the dirt cheap ones from amazon, ebay, or parts stores as they just don't last long.

2007 LEXUS GX470 4.7L V8 Air Spring | RockAuto

RockAuto ships auto parts and body parts from over 300 manufacturers to customers' doors worldwide, all at warehouse prices. Easy to use parts catalog.

www.rockauto.com

If that fixes your problem, then great. If it doesn't, yeah look at some take off parts. While you're under there (take out the spare and you can see a lot more easily) you can trace the lines and inspect them, although they're usually fine. But, I would put money on it being the bags. Mine were kinda intermittent on how much you could notice them sagging when they started to go.

 

[Makakio]

Thanks much. I already have two new Arnott bags waiting to be installed, so will take that advice and get on it. Appreciate the links, thought process and suggestion!

 

[redeyeracing]

Rommell is right. The odds that they aren't both bad is very slim. Dollars to donuts when you swap them out it will fix the problem. Pretty easy fix in my opinion. Took me like 30 min. I do have a car lift though that helped.

 

[thabruiser]

I would like to clarify that in my previous post, I was unsure as to how the system worked. I didn't mean to cause confusion!

 

[Makakio]

Okay guy - so it's likely NOT the bags, but the solenoid (which is impossible to replace w/o buying $1200 worth of crap I don't need). Anyone have a system they might part out???

By the way I have the new bags - but the solenoid piece was actually busted. Brittle POS. Totally fixable, but cannot order that part alone. Want to keep the air suspension, but will do coil swap if have to...

 

[Rednexus]

Once you do the coil conversion you won't miss the bags. Lots of people here have done it and we're all happy wuth the results.