UZS131 Crown Air Suspension Not Remaining Level

[MS112]

Hello

The Crown has unfortunately gone into "Automatic Pimp Mode" again where the rear suspension has lost all air pressure.

The problem occurred yesterday when I came to a stop on an up-hill incline while I was inspecting the radiator for locusts (damn locusts!). I noticed that the air pump was running continously, accompanied by a hissing sound (usually made when it's letting air out), and that the rear suspension had bottomed out. Moving the Crown to a level surface did not fix the problem, and eventually the Height Controller started flashing "NORM"

All struts were replaced about a year ago, and the car has done about 8000km since then, thus I am going to be optimistic and say that it cannot be due to a failed shock. Disconnecting the car battery for 10 minutes to reset the Height Controller, and restarting the car shows the air pump is trying to pump air, but again a continous hissing noise is also heard.

So it is some sort of issue with the control system. Based on my limited knowledge, it could be due to either an actual leak, or the rear suspension height control valve is faulty, or it could be due to a controller fault mistakingly telling the rear suspension to deflate (ie sensor).

So here are my questions:

1. Is the suspension system exactly the same as that found on the LS400 and Soarers?
2. If so can the trouble shooting guide for these cars be used?

The reason being that I have no manual for the UZS131. Of course if someone knows where I can find one, that would be the best case scenario

I would like to know what TEMS thinks is the issue.

Thank you for your time,
Brendon

[CrUZida]

The only things I know about the air suspension system are as follows.

If the suspension bottoms out, and will not pump, you need to jack the car up to reset the sensors.
You can bridge 2 pins in the diagnostics box (Ts and E1 I think?) and one of the lights will flash on the dash if there is a stored code. (search google for some LS400 diagnostics)

Neither of these will probably help, but who knows?

I had an issue with my Celsior's system a while back, so I unplugged the aftermarket control unit, and just ran the factory one, and the problem went away.

[3sgte]

If you hear a hissing sound, the first thing I would do is look for a leak (follow your ears).
If the compressor is pumping air, any you hear a hissing, and the car is riding on the ground, then that sounds like a leak.

If the compressor was not pumping, then I would look elsewhere.

From what I remember of Lexus of that vintage, the diagnosis info for the air suspension was really thin.
Do you have any info at all?

[MS112]

Thank you for your posts

The only things I know about the air suspension system are as follows.

If the suspension bottoms out, and will not pump, you need to jack the car up to reset the sensors.
You can bridge 2 pins in the diagnostics box (Ts and E1 I think?) and one of the lights will flash on the dash if there is a stored code. (search google for some LS400 diagnostics)

Neither of these will probably help, but who knows?

I had an issue with my Celsior's system a while back, so I unplugged the aftermarket control unit, and just ran the factory one, and the problem went away.

So in other words the LS400 diagnostics should apply. I suspected as such but posted here in case knew better.

If you hear a hissing sound, the first thing I would do is look for a leak (follow your ears).
If the compressor is pumping air, any you hear a hissing, and the car is riding on the ground, then that sounds like a leak.

If the compressor was not pumping, then I would look elsewhere.

From what I remember of Lexus of that vintage, the diagnosis info for the air suspension was really thin.
Do you have any info at all?

In short I've got the information I have posted. Only reason I think it may be a controller fault is that the hissing is originating from the same area where I have heard it release air during auto-levelling. Could be that a height control valve has failed. I should also have mentioned that the front of the car is remaining pressurised, so the leak/fault is at least limited to the rear only.

I am hoping the LS400 documentation will give me an idea of where to look for all these potential leak sources.

Cheers,
Brendon

[TheStitt]

the rears share a common height pot and air line, maybe there is a leak or maybe that rear pot gone.

[MS112]

Sorry guys I am an idiot - I have realised I have left out the one piece of valuable information, out and that is the location of the hiss: front left hand quarter, right near the air compressor.

Cheers,
Brendon

["Z" UTE]

MS112, drop int an automotive air con repairer, and get them to slowly pump 2cc's of their magic leak detector fluorescent dye into the running compressor. Or you could buy some dye and inject it yourself. Run the air system, and check all connections using an ultaviolet light. The control valves are accessed by removing the LH inner guard liner. As Luke mentioned, it could simply be a sensor problem. The sensors are optical, and can get dirty inside. Try disconnecting the sensor and operating it independently of the suspension. Just remember these air sytems are very slow to respond, and trouble shooting will take a fair bit if time.

cheers Chuck.

[MS112]

Ok, I have traced the source of the air leak to a unit called the "Dryer Assembly" (click here for Toyodiy site)

It sits next to the air tank and compressor, and receives air input directly from the compressor. The source of the air leak is actually some sort of relief valve, apparently controlled by an electric solenoid. Something may have gone wrong with the solenoid.

Thank you for your answers so far

Cheers,
Brendon

[MS112]

Ok, I took the solenoid off and confirmed that the there is a "click" sound when voltage is applied. It looks exactly like the solenoid used on the A34D hydraulic auto for overdrive. I powered the compressor again and confirmed air was coming out of the hole which the solenoid covers. There was corrosion on the solenoid face. I cleaned it off somewhat and bolted it back on. The air leak is greatly reduced and the car actually started pumping up.

My guess is that the air is leaking past the innermost o-ring, or the solenoid unit itself is not sealing properly - probably account of internal corrosion. Going to try replacing the o-rings.

Thank you for all your suggestions on how to troubleshoot this problem.

Cheers,
Brendon

[CrUZida]

Good to hear it was an easy fix!

[MS112]

Yes it is, air leaks can be (somewhat) easily traced, control system malfunction would have a bit more difficult :/

Just got home from Heathcote where I was temporarily stranded, just outside of Bacchus Marsh I felt the rear suspension start to bottom out again, on arrival the air leak was back. I am glad I was able to get her home at any rate.

Cheers,
Brendon

Note: I tried to give rep to everyone who has contributed, but apparently I cannot!

[The Witzl]

you are lucky you didnt have leaky struts.
I had those.... and they completely sucked to replace.

Not to mention the cost.

[MS112]

Now that you mention it, that would have been even worse - they were all replaced only 1 year ago

Another update:

The o-rings were not the issue like I thought. They are protruding over the edge, not flat, and lightly applying some oil did not improve the seal. So the problem was with the solenoid valve's ability to seal.

One of the things I have observed is that with the solenoid valve removed from the dryer tank, manually running the compressor actually expels a fair bit of water. The issue here appears to be water causing some amount of corrosion in the solenoid valve. It would seem when the car lowers itself, this is the only opportunity for that collected water to be removed?

I run a small amount of CRC though it, and re-attached to the dryer tank. I manually run the compressor, while switching the solenoid on and off in an attempt to flush any crap out. It worked, as after a few cycles it finally started sealing. I repeated the above procedure again.

The leak is now virtually non-existant, and I can actually see the car changing height when the compressor is running. I wouldn't be surprised if it has been an ongoing problem.

I wonder though if the water will eventually cause the solenoid valve to fail again? Or does the presence of water indicate that the dryer has become saturated and needs replacing? I'll be talking to Toyota soon to see if replacement dryer and/or solenoid is available.

Some (bad pics due to low light) pics:

Solenoid valve and dryer tank


Close-up of solenoid and relief valve port.

Cheers,
Brendon