Air Suspension to Standard Conversion?
12-03-11, 05:52 AM
#31
Lexus Test Driver
Wow! Neat test! Thanks for the information. Looks like something pulled from a repair manual? If so, why don't Lexus Service Tech follow this procedure to diagnose problem with vehicle ride? Hard to imagine that these components have a limited lifespan.
Last edited by redrocks; 12-03-11 at 05:55 AM.
12-03-11, 09:24 AM
#33
The Height Control Solenoid Valve ( it is the Compressor Assy ) do get moisture intrusions and thereby there is no " Fail Safe method" Developed by Lexus, What in turn it does it trigger the Height Control Sensor thereby does not to detect any reading with respect to the Height. You will get a "MIL" on the cluster. In July 2005 there was a modified design to the Solenoid Valve but that did not solve the problem, it was a temprorary TSB issued to solve and Lexus smartly knew for the next 2-3 years you would not come back to the dealer and the warranty is out. Most of the models were between 2003-2005 i believe.
12-04-11, 05:17 AM
#34
Lexus Test Driver
The Height Control Solenoid Valve ( it is the Compressor Assy ) do get moisture intrusions and thereby there is no " Fail Safe method" Developed by Lexus, What in turn it does it trigger the Height Control Sensor thereby does not to detect any reading with respect to the Height. You will get a "MIL" on the cluster. In July 2005 there was a modified design to the Solenoid Valve but that did not solve the problem, it was a temprorary TSB issued to solve and Lexus smartly knew for the next 2-3 years you would not come back to the dealer and the warranty is out. Most of the models were between 2003-2005 i believe.
Thanks.
12-04-11, 08:43 AM
#35
Nopes, TZ image represent the Height Control Sensor and not the Compressor Solenoid Assy. To replace the solenoid you have to remove the Rear wheel and the Quarter Panel Mudguard on the LH side . You will then see a Fuel Tank Pipe Protection, You need to remove the clips. They are located behin these protectors. The job involves at least 2 hours, if you have all the tools.
12-04-11, 12:28 PM
#36
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12-04-11, 01:39 PM
#37
Lexus Test Driver
Nopes, TZ image represent the Height Control Sensor and not the Compressor Solenoid Assy. To replace the solenoid you have to remove the Rear wheel and the Quarter Panel Mudguard on the LH side . You will then see a Fuel Tank Pipe Protection, You need to remove the clips. They are located behin these protectors. The job involves at least 2 hours, if you have all the tools.
12-04-11, 07:35 PM
#38
I remember Lexus issued a TSB for the 2004/2005 model specifically to the Height Control issues and the cause was by the Replacement of Solenoid Assy, and they changed the design to this Solenoid & improved the condition, And did solved the Height Control problem to various owners who were under warranty. The Condition to replace the item was if the ECU detected a Error Code C1735 which is stored in the memory, then they would replace it.
12-04-11, 09:50 PM
#39
I think this is the answer. The GX has AVS, which is described as:
"Adaptive Variable Suspension (AVS)
AVS is a computer-controlled system that continuously adjusts shock-absorber damping rates to help provide appropriate ride comfort and handling precision. Sensors monitor wheel speed, engine rpm, steering-wheel movement, brake application and vertical body motion to determine the ideal damping rate for each shock absorber. The driver can also select the ride firmness with the press of a button."
So, it looks like the sensors do control the shock absorbers for "ideal damping rate" according to road conditions, etc.
"Adaptive Variable Suspension (AVS)
AVS is a computer-controlled system that continuously adjusts shock-absorber damping rates to help provide appropriate ride comfort and handling precision. Sensors monitor wheel speed, engine rpm, steering-wheel movement, brake application and vertical body motion to determine the ideal damping rate for each shock absorber. The driver can also select the ride firmness with the press of a button."
So, it looks like the sensors do control the shock absorbers for "ideal damping rate" according to road conditions, etc.
12-04-11, 10:07 PM
#40
I maybe too simplistic in my thinking here, though I feel like I've had good results tinkering with mine. I'm not a lexus tech, so ymmv.
The points of failure seem to be:
- shocks
- airbags
- suspension position sensor
- pump/tank
There appears to be one thing that's adjustable: ride height. ride height can affect the ride:
- too low and it bounces off of the bump stops. I think this is what you guys are feeling when it's riding "harsh". Look for marks on your rear axle. If it's clean under your bumpstops, you're probably too low and/or your shocks are worn (allowing more movement).
- too high and the rear airbags are effectively raising the rear spring rate to raise the rear, which in turn makes the ride harsh.
- just right and you get the great factory ride.
Failure/wear:
- Shocks: they lose their ability to control the movements of suspension, typically gradually over time. If, combined with a rear ride height that's at spec or a bit low, you'll find yourself on the bump stops when going over bumps, far more than when the truck was new.
- Airbags: My guess is that if they fail, they lose the ability to keep the truck at ride height. Your pump would be running all the time, and you'd be bouncing off of the bumpstops.
- Position sensor: looks like failure would simply result in an error on the dash.
- Pump/tank: If they were failing, my guess is you wouldn't be able to reliably raise the rear of the truck.
MANN777, does this sound right? Are there other "failure modes"?
I tried fixing my ride issue by raising the rear suspension, but wasn't satisfied. I replaced the rear shocks, and fine-tuned height, and it feels great. YMMV.
12-05-11, 04:57 AM
#41
Lexus Test Driver
Can you provide a reference for this feature in the GX? I don't think our shocks are this smart. I think they simply adjust damping (compression and rebound) across 4 preset settings. I think they are unaware of other vehicle variables. This is based on a bunch of seat time in cars with "dumb" and "smart" adjustable dampers. FWIW, I actually prefer the "dumb" shocks
http://www.lexus.com/cpo/model_library/GX/2007.html
12-05-11, 05:21 AM
#42
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Seems to me that, if I'm reading MANN777 correctly, a failure of the sensor would fire an error on the dash -- not result in a rougher ride.
I maybe too simplistic in my thinking here, though I feel like I've had good results tinkering with mine. I'm not a lexus tech, so ymmv.
The points of failure seem to be:
- shocks
- airbags
- suspension position sensor
- pump/tank
There appears to be one thing that's adjustable: ride height. ride height can affect the ride:
- too low and it bounces off of the bump stops. I think this is what you guys are feeling when it's riding "harsh". Look for marks on your rear axle. If it's clean under your bumpstops, you're probably too low and/or your shocks are worn (allowing more movement).
- too high and the rear airbags are effectively raising the rear spring rate to raise the rear, which in turn makes the ride harsh.
- just right and you get the great factory ride.
Failure/wear:
- Shocks: they lose their ability to control the movements of suspension, typically gradually over time. If, combined with a rear ride height that's at spec or a bit low, you'll find yourself on the bump stops when going over bumps, far more than when the truck was new.
- Airbags: My guess is that if they fail, they lose the ability to keep the truck at ride height. Your pump would be running all the time, and you'd be bouncing off of the bumpstops.
- Position sensor: looks like failure would simply result in an error on the dash.
- Pump/tank: If they were failing, my guess is you wouldn't be able to reliably raise the rear of the truck.
MANN777, does this sound right? Are there other "failure modes"?
I tried fixing my ride issue by raising the rear suspension, but wasn't satisfied. I replaced the rear shocks, and fine-tuned height, and it feels great. YMMV.
I maybe too simplistic in my thinking here, though I feel like I've had good results tinkering with mine. I'm not a lexus tech, so ymmv.
The points of failure seem to be:
- shocks
- airbags
- suspension position sensor
- pump/tank
There appears to be one thing that's adjustable: ride height. ride height can affect the ride:
- too low and it bounces off of the bump stops. I think this is what you guys are feeling when it's riding "harsh". Look for marks on your rear axle. If it's clean under your bumpstops, you're probably too low and/or your shocks are worn (allowing more movement).
- too high and the rear airbags are effectively raising the rear spring rate to raise the rear, which in turn makes the ride harsh.
- just right and you get the great factory ride.
Failure/wear:
- Shocks: they lose their ability to control the movements of suspension, typically gradually over time. If, combined with a rear ride height that's at spec or a bit low, you'll find yourself on the bump stops when going over bumps, far more than when the truck was new.
- Airbags: My guess is that if they fail, they lose the ability to keep the truck at ride height. Your pump would be running all the time, and you'd be bouncing off of the bumpstops.
- Position sensor: looks like failure would simply result in an error on the dash.
- Pump/tank: If they were failing, my guess is you wouldn't be able to reliably raise the rear of the truck.
MANN777, does this sound right? Are there other "failure modes"?
I tried fixing my ride issue by raising the rear suspension, but wasn't satisfied. I replaced the rear shocks, and fine-tuned height, and it feels great. YMMV.
12-05-11, 06:13 AM
#43
This is a good summary.
What I am feeling is not "bottoming out" or hitting the bump stops. What I feel is poor rebounding dampening. It's best descrived as hard bottoming when I go over a sharp speed bump, but again my shocks are not bottoming out, not even close. The shock compresses, the rear of the truck rises and I assume the leveling suspension starts to try and level the rear end at this point and starts filling the bag. Once the rear wheel comes down off of the bump, the shock extends, the rear end comes down, but doesn't bounce or sag, it stays level, and bam, hard bottom. It feels to me like the rear leveling suspension is over reacting to the speed bumps and by the time my truck comes off the bump the bag is arleady filled with air resulting in the poor rebounding dampening.
The suspension is set to the 2nd most comfortable position. On comfort the suspension is less prone to exhibit this behavior. My GX sits even, the air/leveling suspension appears to be funcition correctly, adjusts to the slightest weight added to the back or vice versa. Other than the hard bottoming issue it rides great. Perhaps bad compression valves in the shocks?
What I am feeling is not "bottoming out" or hitting the bump stops. What I feel is poor rebounding dampening. It's best descrived as hard bottoming when I go over a sharp speed bump, but again my shocks are not bottoming out, not even close. The shock compresses, the rear of the truck rises and I assume the leveling suspension starts to try and level the rear end at this point and starts filling the bag. Once the rear wheel comes down off of the bump, the shock extends, the rear end comes down, but doesn't bounce or sag, it stays level, and bam, hard bottom. It feels to me like the rear leveling suspension is over reacting to the speed bumps and by the time my truck comes off the bump the bag is arleady filled with air resulting in the poor rebounding dampening.
The suspension is set to the 2nd most comfortable position. On comfort the suspension is less prone to exhibit this behavior. My GX sits even, the air/leveling suspension appears to be funcition correctly, adjusts to the slightest weight added to the back or vice versa. Other than the hard bottoming issue it rides great. Perhaps bad compression valves in the shocks?
Seems to me that, if I'm reading MANN777 correctly, a failure of the sensor would fire an error on the dash -- not result in a rougher ride.
I maybe too simplistic in my thinking here, though I feel like I've had good results tinkering with mine. I'm not a lexus tech, so ymmv.
The points of failure seem to be:
- shocks
- airbags
- suspension position sensor
- pump/tank
There appears to be one thing that's adjustable: ride height. ride height can affect the ride:
- too low and it bounces off of the bump stops. I think this is what you guys are feeling when it's riding "harsh". Look for marks on your rear axle. If it's clean under your bumpstops, you're probably too low and/or your shocks are worn (allowing more movement).
- too high and the rear airbags are effectively raising the rear spring rate to raise the rear, which in turn makes the ride harsh.
- just right and you get the great factory ride.
Failure/wear:
- Shocks: they lose their ability to control the movements of suspension, typically gradually over time. If, combined with a rear ride height that's at spec or a bit low, you'll find yourself on the bump stops when going over bumps, far more than when the truck was new.
- Airbags: My guess is that if they fail, they lose the ability to keep the truck at ride height. Your pump would be running all the time, and you'd be bouncing off of the bumpstops.
- Position sensor: looks like failure would simply result in an error on the dash.
- Pump/tank: If they were failing, my guess is you wouldn't be able to reliably raise the rear of the truck.
MANN777, does this sound right? Are there other "failure modes"?
I tried fixing my ride issue by raising the rear suspension, but wasn't satisfied. I replaced the rear shocks, and fine-tuned height, and it feels great. YMMV.
I maybe too simplistic in my thinking here, though I feel like I've had good results tinkering with mine. I'm not a lexus tech, so ymmv.
The points of failure seem to be:
- shocks
- airbags
- suspension position sensor
- pump/tank
There appears to be one thing that's adjustable: ride height. ride height can affect the ride:
- too low and it bounces off of the bump stops. I think this is what you guys are feeling when it's riding "harsh". Look for marks on your rear axle. If it's clean under your bumpstops, you're probably too low and/or your shocks are worn (allowing more movement).
- too high and the rear airbags are effectively raising the rear spring rate to raise the rear, which in turn makes the ride harsh.
- just right and you get the great factory ride.
Failure/wear:
- Shocks: they lose their ability to control the movements of suspension, typically gradually over time. If, combined with a rear ride height that's at spec or a bit low, you'll find yourself on the bump stops when going over bumps, far more than when the truck was new.
- Airbags: My guess is that if they fail, they lose the ability to keep the truck at ride height. Your pump would be running all the time, and you'd be bouncing off of the bumpstops.
- Position sensor: looks like failure would simply result in an error on the dash.
- Pump/tank: If they were failing, my guess is you wouldn't be able to reliably raise the rear of the truck.
MANN777, does this sound right? Are there other "failure modes"?
I tried fixing my ride issue by raising the rear suspension, but wasn't satisfied. I replaced the rear shocks, and fine-tuned height, and it feels great. YMMV.
12-05-11, 08:25 AM
#45
i think most of you guys are trying to fix something that doesn't need fixing.
like someone stated, there aren't many posts here stating they're having issues with their air suspension.
like someone stated, there aren't many posts here stating they're having issues with their air suspension.