Is my AHC dead?

[Tareq]

Hello,

I had my LX470 for 3 months now, AHC was working flawlessly, but I have been offroading almost every weekend since I got it for the purpose of a trip that I should have started already.

This weekend and the weekend before, AHC refused to go up to H, it just blinks then stays in N, one time it went to L in the middle of the trail. I tried restarting the car, it went back to N but will not go to H?

What is happening?

I thought of OME conversion, but dont feel like investing in it if I dont have the intention of keeping the car for the long term after my trip ,,,,, any quick fix?

btw, AHC fluid level is good and clean!!

 

[jLB]

Have you checked AHC pressure(s) with TechStream?

Have you been through are the AHC troubleshooting threads on the forum? (There are more than a few.)

Alternative "cheap" fix, try to find some non-AHC take-off springs and some new OEM shocks, but there's still a fair bit of labor involved.

 

[FranceJohnson]

First, you should figure out the condition of your ahc fluid. Good chance it is toast and the pump just can't build the crazy high pressures needed to move the truck up and down.

TechStream will tell you the pressures which is nice. You can hit the front torsion bars to take some pressure off the system. I have just under 300K on my ahc system, and its still kicking.

I would first bleed the system, which takes about 1.5 cans of the fluid.

 

[Tareq]

Have you checked AHC pressure(s) with TechStream?

Have you been through are the AHC troubleshooting threads on the forum? (There are more than a few.)

Alternative "cheap" fix, try to find some non-AHC take-off springs and some new OEM shocks, but there's still a fair bit of labor involved.

First, you should figure out the condition of your ahc fluid. Good chance it is toast and the pump just can't build the crazy high pressures needed to move the truck up and down.

TechStream will tell you the pressures which is nice. You can hit the front torsion bars to take some pressure off the system. I have just under 300K on my ahc system, and its still kicking.

I would first bleed the system, which takes about 1.5 cans of the fluid.

Thank you for ur input guys,
I havent used Techstream before and I am not mechanically inclined either,,

As I mentioned, AHC fluid level is good, between Low and High, and the Fluid is clear (clean), was flushed last year according to po, but I am suspicious he just changed the fluid in the reservoir,,,,,

I forgot to mention that the system always acts up on the trail AFTER water crossings
The mechanic showed me the sensor which is near the diff breather.
He said the elements make the sensor "confused" about the environement the car is in.

Today I tried it at work, it went up and down just fine!! Flawless!

I understand the system needs pressure to raise it to H, but what explains that it wont go Low either when I try, unless it acts up and just goes there by itself?


Finally, the reason that pushes me towards changing the system to regular suspension is that the ride is grossly uncomfortable!!!
The shocks are rough, there is no absorption of bumps, it is almost like u are riding on heavy rated coils without any shocks,,,, not bouncy, but jittery ,,,, all LXs I test drove were Cadillac like smooth

When I go over bumps, the whole car lifts and drops as if there are no shocks to absorb

AHC fluid not available at local dealers, they say it is obsolete when I checked when I got the car
Let me call them again,,,

If I know 100% I will keep the car I would have paid for OME as soon as I bought it

Thank you again!!

 

[geanes]

"AHC fluid not available at local dealers, they say it is obsolete when I checked when I got the car
Let me call them again,,,"

First off, get another dealer. Both Toyota and Lexus dealers here in Austin knew exactly what the AHC fluid was/is, knew that there was a new part number and had it in stock.

"The shocks are rough, there is no absorption of bumps, it is almost like u are riding on heavy rated coils without any shocks,,,, not bouncy, but jittery ,,,, all LXs I test drove were Cadillac like smooth"

Sounds to me like the hydraulic suspension is taking the brunt of the suspension load. Shouldn't be that way. Ideally, it's about 60% springs/torsion bars and 40% hydraulic. When it feels "sharp" that usually indicates the hydraulics are bearing the major part of the load. Cross level the front by measuring the height of each side from the center of the hub to the top of the wheel arch. Do this by cranking the low side clockwise (tightens) and the high side counterclockwise (loosens). Do this in 1/4 turn increments. Flex the suspension and remeasure. Repeat until both sides are withing 1/4 inch of each other. Once that's done, start cranking both torsion bars equally. Mine rode harsh as well. I cranked the bars 7 total rotations over 4 occurrences (2 + 2+ 2 + 1). Once that was done, my LX rides like a Cadillac.....a reliable Cadillac with significantly better build quality and reliability....actually, it rides like a Lexus...which is better

Ultimately, you need to run techstream to understand your pressures. Mine started off with 8.2 up front and 7.9 in the rear. Ideally, an LX should be between 6.7-6.9 in the front and 5.9-6.7 in the rear. The front is easy to adjust as it's simply cranking the torsion bars. The rear is more complicated as it requires either spring replacement (kings are very popular for LXs) and/or 30mm spacers.

I have a sneaky feeling that if you crank the torsion bars, the great majority of your issues would be resolved. I got lucky and found a fellow mud member here in Austin that allowed me to use their techstream to troubleshoot and fix my AHC.

 

[Tareq]

"AHC fluid not available at local dealers, they say it is obsolete when I checked when I got the car
Let me call them again,,,"

First off, get another dealer. Both Toyota and Lexus dealers here in Austin knew exactly what the AHC fluid was/is, knew that there was a new part number and had it in stock.

"The shocks are rough, there is no absorption of bumps, it is almost like u are riding on heavy rated coils without any shocks,,,, not bouncy, but jittery ,,,, all LXs I test drove were Cadillac like smooth"

Sounds to me like the hydraulic suspension is taking the brunt of the suspension load. Shouldn't be that way. Ideally, it's about 60% springs/torsion bars and 40% hydraulic. When it feels "sharp" that usually indicates the hydraulics are bearing the major part of the load. Cross level the front by measuring the height of each side from the center of the hub to the top of the wheel arch. Do this by cranking the low side clockwise (tightens) and the high side counterclockwise (loosens). Do this in 1/4 turn increments. Flex the suspension and remeasure. Repeat until both sides are withing 1/4 inch of each other. Once that's done, start cranking both torsion bars equally. Mine rode harsh as well. I cranked the bars 7 total rotations over 4 occurrences (2 + 2+ 2 + 1). Once that was done, my LX rides like a Cadillac.....a reliable Cadillac with significantly better build quality and reliability....actually, it rides like a Lexus...which is better

Ultimately, you need to run techstream to understand your pressures. Mine started off with 8.2 up front and 7.9 in the rear. Ideally, an LX should be between 6.7-6.9 in the front and 5.9-6.7 in the rear. The front is easy to adjust as it's simply cranking the torsion bars. The rear is more complicated as it requires either spring replacement (kings are very popular for LXs) and/or 30mm spacers.

I have a sneaky feeling that if you crank the torsion bars, the great majority of your issues would be resolved. I got lucky and found a fellow mud member here in Austin that allowed me to use their techstream to troubleshoot and fix my AHC.

I appreciate your input,
Will send it to my mechanic for review and will perform the exercise soon.
Will call 3 to 4 Lexus dealers to see if they have AHC fluids or not.
In Canada we dont have LCs, so Toyota dont have AHC fluids.

Thank you once again !!!

 

[geanes]

I appreciate your input,
Will send it to my mechanic for review and will perform the exercise soon.
Will call 3 to 4 Lexus dealers to see if they have AHC fluids or not.
In Canada we dont have LCs, so Toyota dont have AHC fluids.

Thank you once again !!!

Ah, forgot that you're in Canada. I just bought 3 litres of the AHC fluid from my Lexus dealer here in TX. They charged $15/litre. I believe some have found it thru online sources for as little as $11/litre.

BTW, the simplest way to adjust the torsion bars is to put the vehicle in High (if possible), PB blast the bolt on each side (if necessary) and then use a breaker bar with a 30mm socket. Literally takes 2 minutes to crank both sides 2-3 rotations. Good luck. When functioning properly, I believe the AHC to be the nicest suspension out there.....even at 20 years old

 

[1meancruiser]

my suggestion is to crank up the torsion bars. Do so until the car is unable to get into low, and then back off half a turn. also, it's likely you rear springs are shot. They only have a five year lifespan so depending on the last time it was changed, they may be due. I had that issue happen several times when I first got my LC. The prior owner never adjusted the torsion bars and the rear springs were 8 years old. and the weight of the vehicle was being handled by the AHC. when loaded up on a trail, it was too much. Lastly, I'm selling a set of rear AHC springs, having taken the system off the LC. I'm not telling you to buy, I'm letting you know in case your rears are warn.

 

[geanes]

my suggestion is to crank up the torsion bars. Do so until the car is unable to get into low, and then back off half a turn. also, it's likely you rear springs are shot. They only have a five year lifespan so depending on the last time it was changed, they may be due. I had that issue happen several times when I first got my LC. The prior owner never adjusted the torsion bars and the rear springs were 8 years old. and the weight of the vehicle was being handled by the AHC. when loaded up on a trail, it was too much. Lastly, I'm selling a set of rear AHC springs, having taken the system off the LC. I'm not telling you to buy, I'm letting you know in case your rears are warn.

How old are your springs? I'm a little over the 5 year deadline (by like 3 years). Rides fine now, but I'm on borrowed time. Thought about keeping mine and running AirLift adjustable air bags.

 

[Tareq]

Ok, so Lexus near me has AHC, will buy one, do complete flush, and see if this makes a difference before I go ahead with further steps ,,,,, will update u in 2 days maximum ,,,, thanks!!!

 

[geanes]

@Tareq .... I'm sure you've seen it, but here are two videos that I think are excellent instructional ones for swapping rear springs/adding spacers and the AHC flush/refill

 

[PADDO]

Erratic height control behavior after water crossings? You'd really want to look at height sensor/harness moisture ingress as the root of the problem. Not an uncommon fault at all. A hard ride can be due to poor maintenance (high pressures/gassy old depleted fluid) aged or blown damper accumulators and a few other things including the system defaulting to max hard dampening under some fault conditions. I'd work on resolving the water crossing related height control issue as the first priority.

 

[2001LC]

Try water hose on sensor/harness while AHC working, see if can duplicate condition.

 

[Tareq]

Ok guys, this is a quick write up and will get back to u after work,,

I did flush AHC this morning,
1st, turkey baster to take almost all out of reservoir, contrary to my belief, it was BLACK!

2nd, started in the driver side, came out fffffast!! brown cappuccino colour.

3rd, had trouble removing other side due to rusty nuts, 10mm did not fit so had to spray wd-40 and use (not sure what it is called) to twist the nuts.

I wasnt sure the nuts were twisting so I kept twisting until I got the bleeding valve came out on 2 of the 3 corners.
Sprayed it with wd40 to clean and put it back
On the 3 corners almost nothing came out, just little fluid, was it starved?
I am sure air went into the system when the valves came out,,,

Finally, I did not know how to bleed that big cylinder under the driver's side because I couldnt find the bleeding point. The is a BIG plastic cap on the front side but could not remove it.

Strated the LX, and put on H ,,, after slight hesitation, it started working!
more than 30 time up and down not problem,,, took it for short drive, still rough, but I think I need to let new fluids circulate..

Now the LX is in Low, and the reservoir is almost full of fluid.

Once I know how to bleed that cylinder it should be good.

Previous owner clearly lied about flushing it ,,, I think this is the first time in the LX's life

Sorry for fast write up ,,, back later tonight ,,, thank you all!!!!

 

[geanes]

Yeah, AHC fluid shouldn't be black or brown. Did you have any "froth" aka bubbles in the fluid that was bled? If not, you are very lucky. If so, that is usually a sign that the nitrogen in the globes is nearing the end of it's life and need replacing.

The big cylinder is the accumulator and needs to be bled as well. First pic is of the entire assembly. The bleed valve is not covered by the big plastic cap. In the second photo of the actual height accumulator, you'll notice the bleed as the brass colored valve in the lower left.

 

[Tareq]

Yeah, AHC fluid shouldn't be black or brown. Did you have any "froth" aka bubbles in the fluid that was bled? If not, you are very lucky. If so, that is usually a sign that the nitrogen in the globes is nearing the end of it's life and need replacing.

The big cylinder is the accumulator and needs to be bled as well. First pic is of the entire assembly. The bleed valve is not covered by the big plastic cap. In the second photo of the actual height accumulator, you'll notice the bleed as the brass colored valve in the lower left.

View attachment 1505114

View attachment 1505115

It was BLACK from the reservoir, but from the driver's side valve it was clear then brown, no bubles but almost like the top of a cappuccino cup stuff. The other valves pretty much didnt get out much fluid, almost nothing.
Now that it is all in the same bottle it is all black.

As I mentioned, 2 valves came all the way out.

Yes, I saw the diagram and the video u attached, thank you, but mine just does not have that bleeding valve!
It only has the dome shaped plastic in the front, and electric wire from the back,
Mine is 2003, Canadian spec, is it any different than other years or specs?
Maintenance record from dealer shows no history of AHC related work in case the cylinder was replaced with a new part that does not have the valve?!

I am confused.

The fluid in the reservoir now went down a bit, maybe the fluid filled the air gap that came in when I took off the valves.

 

[PADDO]

It's very unlikely that any air of significance entered the system. I suspect your height accumulator bleeder may have been broken off, post up a close up photo of the front of the height accumulator. The bleeder port should be located adjacent to the solenoid (aka thingy covered with big plastic cap). Did you follow the bleeding procedure and let the vehicle drop to the bump stops so it can expel as much fluid as possible?

 

[Tareq]

It's very unlikely that any air of significance entered the system. I suspect your height accumulator bleeder may have been broken off, post up a close up photo of the front of the height accumulator. The bleeder port should be located adjacent to the solenoid (aka thingy covered with big plastic cap). Did you follow the bleeding procedure and let the vehicle drop to the bump stops so it can expel as much fluid as possible?

The bleeder port is not broken off, it is just not there,,
I will go take photo now, it is not there,,
All 4 corners went all the way down the LX was leveled like a toyota camry,,, front first then back, as I mentioned, when 2 bleeders came all the way out, I think this means nothing was holding any fluid inside the system.

I will get back with a photo shortly, thank you!!

 

[Tareq]

Yeah, AHC fluid shouldn't be black or brown. Did you have any "froth" aka bubbles in the fluid that was bled? If not, you are very lucky. If so, that is usually a sign that the nitrogen in the globes is nearing the end of it's life and need replacing.

The big cylinder is the accumulator and needs to be bled as well. First pic is of the entire assembly. The bleed valve is not covered by the big plastic cap. In the second photo of the actual height accumulator, you'll notice the bleed as the brass colored valve in the lower left.

View attachment 1505114

View attachment 1505115

 

[PADDO]

Scrape off the mud and any anti rust coating or whatever on the front face and you'll find where the bleeder should be. I can see what appears like a "patch" over the bleed port.