Question about AHC operation

[wgs]

I have been looking at an '03 LX470 and am getting ready to pull the trigger. I am a little concerned about the AHC system, however. When I test drove the vehicle the AHC raised and lowered the vehicle, but I'm not sure if it worked as it should have. When I changed the height, it seemed to raise rear first then front. Is that normal? I have searched the manual and the forums, and have not seen any info as to how the truck should raise. I would have assumed it would go up level, but maybe what I observed is normal. It seemed to drive normal and was not bouncy, so I think the system is OK, but really want to be sure I am not buying something that will immediately need a costly suspension job.
Thanks,
Bill

 

[RKRUGER]

It is an open system so the fluid(that fills the hydraulic cylinders) will always go to the path of least resistance. Adjusting the TB might give some assistance. But as the engine is in front, I guess what I am saying is this doesn't seem unusual.

 

[Jimthom]

Mine also behaves like that. The front and rear move up or down sometimes at different rates, then it settles in.
Check the AHC threads for the proper change in fluid level in the reservoir, should be more than 7 from L to H.
And you should be able to tell the difference between the Comfort and Sport settings on the shocks.
The FSM has more details on the rates of lift and heights.

 

[PADDO]

I have been looking at an '03 LX470 and am getting ready to pull the trigger. I am a little concerned about the AHC system, however. When I test drove the vehicle the AHC raised and lowered the vehicle, but I'm not sure if it worked as it should have. When I changed the height, it seemed to raise rear first then front. Is that normal? I have searched the manual and the forums, and have not seen any info as to how the truck should raise. I would have assumed it would go up level, but maybe what I observed is normal. It seemed to drive normal and was not bouncy, so I think the system is OK, but really want to be sure I am not buying something that will immediately need a costly suspension job.
Thanks,
Bill

Normal. It will raise level until the height accumulator pressure is exhausted and then it will switch to rear lifting (to keep the headlights from blinding people) then the front will come up to complete the raising and leveling process. Opposite for lowering. There have been any number of threads on checking out AHC systems for first timers, they can be a bit hard to search and follow cause they often get off topic pretty quickly. For a quick car lot check out: engine running, doors shut and foot off brake does it raise and lower ok? this can take up to 15 seconds or so. Is the fluid level in the ps firewall reservoir between max and min at N height? Now put the vehicle in L and observe the fluid height, now put the vehicle in H and observe fluid height noting the number of graduations difference on the reservoir side, good/ok for a used vehicle is 9 to 11 grads, less than 7 the damper globes are done probably (this test is most accurate when the neutral pressures are in spec but that needs test equipment to check). During road test does it respond to the damping control switch? Comfort setting should be soft and squishy up to sport 2 which should be quite firm. Ride quality is subjective but you should feel a significant difference between comfort and sport 2. So, if it raised and lowers with no constant flashing AHC light and responds to the damper settings and you have more than 7 ideally 9-12 grads (4x new damper globes gives you close to 14) on the tank you've done about as much as you can to verify operation without hooking up a tester etc.

 

[wgs]

Thanks all for your feedback on this. I'll be sure to thoroughly test out the system before I decide to purchase the truck.
Hopefully it passes the test!
-Bill

 

[Wilsil]

It will raise the rear first as not to blind the oncoming cars, then the front.