AHC troubleshooting

[burtonlx]

Hi. I bought a 2000 LX470 in 2008. It has 80,000 miles and it's been a great car.

I am looking for some help troubleshooting an AHC problem.

Since I bought the LX it's has a very stiff ride. Not bouncy, but stiff -- almost as if there's no shock dampening.

The LX isn't used off road, doesn't tow anything and isn't used to carry unusually heavy loads.

I have installed new Michelin LTX tires and I keep an eye on tire pressures, but the rough ride hasn't improved. I think I can rule out a tire problem.

The AHC system goes from normal height to high and low without doing anything unusual. THe AHC fluid moves 9 notches on the AHC fluid reservoir from low to high height. I think I can rule out an AHC pump problem.

The LX sits normally, not low to the grounds as I've read can happen if the accumulators go. And when I press down on the corner of each bumper, the suspension moves and rebounds as you'd expect. I've read that if the accumulators are bad the suspension won't move much. Based on what I've read I think I can rule out an accumulator problem.

On to the AHC fluid: at the normal height setting, the fluid level in the reservoir is a couple of notches below the minimum level. I asked my dealer last year if the AHC fluid should be flushed. He said no, unless there's a problem. But I just noticed that the owner's manual recommends the AHC fluid should be changed at 60k miles. I have all of the service records for the car and and the AHC fluid has never been flushed. Is it possible that changing the AHC fluid or at least filling the reservoir to above the minimum level will help the ride quality?

I mostly understand how the accumulators work. Is it possible that the shocks on the LX are bad based on age and / or mileage? Do the shocks on an LX470 with AHC effect ride quality?

Finally, if the suspenion is out of spec could that be the problem? For example, could the neutral pressure be set incorrectly or the torsion bars not be tightened properly?

If I can get some troubleshooting advice from you all then I'll be able to steer my dealer in the right direction. I don;t want the dealer to randomly start changing (expensive) parts without. Thank you.

 

[CappyKD]

Is this with the suspension on the left most comfort setting?

 

[burtonlx]

Sorry I didn't mention that. I've tried all of the suspension settings. Ride quality is obviously subjective, but to me if feels least bad on the 2nd highest sport setting. That's where I leave it -- one click from the right most sport setting. The comfort settings feel more harsh, which is counterintuitive.

 

[CappyKD]

hmmm the comfort settings make mine ride like a big old caddy. in sport the ride is noticably rougher. hmm.

 

[snapaxle]

The LX's don't really have shocks, the only problem I have seen with those is that they can leak over time. Then they will need to be replaced. If the globes / accumulators are flat, it will still raise and lower, the ride just goes to hell.

https://forum.ih8mud.com/100-series-cruisers/507200-ahc-my-accumulators-dead.html

They have a pretty decent run down in this thread.

 

[lexi4darin]

On to the AHC fluid: at the normal height setting, the fluid level in the reservoir is a couple of notches below the minimum level. I asked my dealer last year if the AHC fluid should be flushed. He said no, unless there's a problem. But I just noticed that the owner's manual recommends the AHC fluid should be changed at 60k miles. I have all of the service records for the car and and the AHC fluid has never been flushed. Is it possible that changing the AHC fluid or at least filling the reservoir to above the minimum level will help the ride quality?

I mostly understand how the accumulators work. Is it possible that the shocks on the LX are bad based on age and / or mileage? Do the shocks on an LX470 with AHC effect ride quality?

Finally, if the suspenion is out of spec could that be the problem? For example, could the neutral pressure be set incorrectly or the torsion bars not be tightened properly?

Absolutely flush the AHC system yourself. It takes an hour or two and is very very easy. It will improve the ride and feel of the suspension. Also if you're below the minimal fluid level in the reservoir, you can inadvertently suck air into the the system and cause a major change to the way the hydraulics will work...and thusly you're going to feel it in the ride responsiveness.

However, I'd recommend doing a flush yourself rather than allowing the dealer to do so. It will cost about $60 for the fluid and an hour or two of your time. Doing it yourself avoids the likely scenario of the dealer just topping off your fluid and then saying, "told ya flushes don't matter; the real cause is xyz $$$$$".

Also you're torsion bars are the main adjustment to the AHC neutral pressure. Try adjusting this correctly by turning the bolt on the torsion bar (also very easy to DIY). IF you're ride is already very stiff, you'll want to unload some of the spring in the torsion bars.

 

[burtonlx]

Thanks for including this link. I read this thread last week when I began my AHC education on this site.

Could a leaky shock impact ride quality? My LX's ride isn't bouncy, just rough. From what I've read when the accumulators go the ride gets bouncy, not rough. Will a leaky shock be noticeable if I stick my head under the car?

The LX's don't really have shocks, the only problem I have seen with those is that they can leak over time. Then they will need to be replaced. If the globes / accumulators are flat, it will still raise and lower, the ride just goes to ****.

https://forum.ih8mud.com/100-series-cruisers/507200-ahc-my-accumulators-dead.html

They have a pretty decent run down in this thread.

 

[burtonlx]

Thanks for the encouragement to flush the system myself. I've never tried something like this (or loosening the torsion bars), but I may give this a shot.

I bought the AHC fluid today and topped off the reservior. It was $50 for a 2.5L cannister. Probably pretty good margins in that for Toyota.

Absolutely flush the AHC system yourself. It takes an hour or two and is very very easy. It will improve the ride and feel of the suspension. Also if you're below the minimal fluid level in the reservoir, you can inadvertently suck air into the the system and cause a major change to the way the hydraulics will work...and thusly you're going to feel it in the ride responsiveness.

However, I'd recommend doing a flush yourself rather than allowing the dealer to do so. It will cost about $60 for the fluid and an hour or two of your time. Doing it yourself avoids the likely scenario of the dealer just topping off your fluid and then saying, "told ya flushes don't matter; the real cause is xyz $$$$$".

Also you're torsion bars are the main adjustment to the AHC neutral pressure. Try adjusting this correctly by turning the bolt on the torsion bar (also very easy to DIY). IF you're ride is already very stiff, you'll want to unload some of the spring in the torsion bars.