Intermittent Suspension Issue

[Gebomartin]

I sold my GX470 to my son at 130,000 miles. He says every now and then it starts riding hard like my old 2002 4Runner. Like the shocks are solid with no give. We drove it yesterday and all was well. He drove it to work today and about 30 minutes going up the road it
started riding so hard he chipped a tooth and might have cracked C5. Then...2 minutes later smooth as cream cheese. No dash lights
are on. Haven't scanned it yet. If it were the air bags, would it behave like this? It does have air suspension on the rear only. Any thing
you suggest I do to start my diagnosis? He has the dial set to "Comfort" mode

 

[Gebomartin]

If I decide to convert from rear air suspension to a normal coil spring OEM setup, what OEM parts would I need? Does Lexus have the setup as a "kit"? I guess I can call Bell Lexus. We are only going back OEM if we go back to the coil setup.

 

[Stonefoot72]

I've had the bad fortune of having to nurse mine 30 miles back to civilization on my rear bump stops after airbag failure.

What you are describing sounds like airbag deflation. Perhaps a slow leak unlike my catastrophic failure. The pitch of its stance would be pretty noticeable at rest if the bags were down (front end visually higher).

Are the symptoms only after letting it sit for a time and then getting better, or is it alternating between broken vertabrae and Lexus smooth during operation?

It's possible they are leaking down after sitting, and slowly airing back up as he drives, resulting in soft ride again.

If it happens intermittently while driving, that would indicate something else to me. If the compressor can air them back up faster than the leak, I would expect them to stay up while operating.

If airbags are the issue, and you are able to do the work yourself, replacing the leaking component (bags, lines, or compressor) can be done pretty easy. The other option is replacing airbags with springs. This forum has a lot of info on both procedures. I went with springs, but mine is built up. Bags are better for normal operation IMHO.

 

[Gebomartin]

I've had the bad fortune of having to nurse mine 30 miles back to civilization on my rear bump stops after airbag failure.

What you are describing sounds like airbag deflation. Perhaps a slow leak unlike my catastrophic failure. The pitch of its stance would be pretty noticeable at rest if the bags were down (front end visually higher).

Are the symptoms only after letting it sit for a time and then getting better, or is it alternating between broken vertabrae and Lexus smooth during operation?

It's possible they are leaking down after sitting, and slowly airing back up as he drives, resulting in soft ride again.

If it happens intermittently while driving, that would indicate something else to me. If the compressor can air them back up faster than the leak, I would expect them to stay up while operating.

If airbags are the issue, and you are able to do the work yourself, replacing the leaking component (bags, lines, or compressor) can be done pretty easy. The other option is replacing airbags with springs. This forum has a lot of info on both procedures. I went with springs, but mine is built up. Bags are better for normal operation IMHO.

It is alternating. That is the part that is baffling to me??

After sitting overnight and leaving for work in the morning, all is well. After driving continuously from 30 min to an hour, all is still well. Then it messes up and fixes itself in a few minutes.

I guess we should measure both sides of the rear when he gets home and then measure both sides in the morning. If it leaks down it will obviously show up.

Are there other procedures we could try to help narrow the issue down? I'm gonna scan for codes before the weekend.

 

[Rednexus]

The airbags in these can slowly dry rot over time and develop micro-cracks. Mine had intermittent leaking for some time. I think the bags would flex and lose air when the micro-cracks opened up, but sometimes they would close up and not leak. If you inspect the bags and the surface has small cracks in it, that is probably your issue.

I'd suggest just coil converting it. It is a straightforward exercise and will be more reliable. There are a number of coil conversion kits out there for around $100, although you'd also need a set of stock-height coil springs and rubber isolators (both of which can be ordered or obtained from a 2003-2023 4Runner). It could probably be done for around $300 all in with new aftermarket parts, but maybe cheaper if you can source used/takeoff springs and isolators from a 4Runner.

 

[Stonefoot72]

Yeah, thats a mystery. I'm struggling to believe that those shocks, at any setting, could get that hard. Having said that, If it were me, I'd suspect the ride controller. Disconnect the shock actuators either at the individual shock, or find the fuse for the ride controller and see if the intermittence stops at least.

There are a lot of smart guys on here that may chip in with more refined troubleshooting, but thats where I'd start.

 

[Gebomartin]

Yeah, thats a mystery. I'm struggling to believe that those shocks, at any setting, could get that hard. Having said that, If it were me, I'd suspect the ride controller. Disconnect the shock actuators either at the individual shock, or find the fuse for the ride controller and see if the intermittence stops at least.

There are a lot of smart guys on here that may chip in with more refined troubleshooting, but thats where I'd start.

I'll look for that fuse.

 

[Gebomartin]

Well, I was able to get the GX in my possession. I turned the switch from H to N to low. About 2 inches between each setting. 4 inches total. Ran a scan and found no codes. On my way taking it back home. it started the hard ride in the rear again. Got it in my garage and measured, and it was at the lowest setting. I press the switch to high and it raisedit up to the N setting. Now the green light is stuck in the H position and I can’t move it back to the N or low. Apparently the switch is bad.????