1200 miles trip and issues with AHC.

[1meancruiser]

I went on a long road trip from southern California, through northern Nevada and I had some issues with the AHC. after covering about 400 miles with around 800 lbs of people and gear in my car and in 95F temps, I came to a stop (i got pulled over by Nevada HP) and i noticed the car lowered itself intially, kind of harshly as soon as i came to a stop. I put the AHC in low and kept the car running. after a 20 minute stop, i started driving again and although the car felt higher and drove smooth, the AHC would not come out of LOW setting. after 40 more miles we took a one hour stop. everything was fine after.

Is this normal, did i just overheat the system?

The LC is a 2006 with 23k miles on it, so far from the system being worn out.

also, has anyone tried to attach heatshields between the exhaust manifolds and the AHC system, it seems the exhaust manifold would just contribute to heating up the system?

 

[rmhrc630]

I went on a long road trip from southern California, through northern Nevada and I had some issues with the AHC. after covering about 400 miles with around 800 lbs of people and gear in my car and in 95F temps, I came to a stop (i got pulled over by Nevada HP) and i noticed the car lowered itself intially, kind of harshly as soon as i came to a stop. I put the AHC in low and kept the car running. after a 20 minute stop, i started driving again and although the car felt higher and drove smooth, the AHC would not come out of LOW setting. after 40 more miles we took a one hour stop. everything was fine after.

Is this normal, did i just overheat the system?

The LC is a 2006 with 23k miles on it, so far from the system being worn out.

also, has anyone tried to attach heatshields between the exhaust manifolds and the AHC system, it seems the exhaust manifold would just contribute to heating up the system?

In my experience that is not abnormal. The ahc will say its in low when you're cruising down the highway doing 100km/hr. I also think that temp is not that vital as mind dropped itself even in coldish temps.

 

[hkeller]

It is not normal for the AHC to stay in low. It raises out of low at 9 mph. This is in the owner's manual. In low, you are essentially riding on the bumpstops.

 

[rmhrc630]

It is not normal for the AHC to stay in low. It raises out of low at 9 mph. This is in the owner's manual. In low, you are essentially riding on the bumpstops.

The point I think we are making is that while the light might be saying its in low, in actual fact the vehicle is in normal.

I've driven for and hour or so like this. It's part of the skyhook tems system.

 

[Kigiin]

Mine goes in low all the time fully loaded - it's not really low though, just not normal height.

Matter of fact, I had this issue years ago (at around 40-50K miles) without the bumpers, winch, aux fuel tank, etc., but when loaded with 4 guys and a bunch of hunting/camping equipment.

 

[hkeller]

Let's see what uHu thinks about this. He seems to have one the best grasps of the AHC system. I still don't think it is "normal" for the AHC system to be showing an indicator light for low at speeds above 9 mph, which was the OPs question.

 

[pman]

It says in the manual that if you have a lot of weight (800 lbs definetly qualifies) it is normal for AHC to say it is in Low. It also says that it is okay to drive like this.

The sudden drop when you came to a stop is normal too, the system does not adjust the height when you are moving fast.

Our LX will occasionally do this when we are towing our boat.

Its also extremely difficult to make AHC overheat.....it has a ton of fluid in it

 

[TeCKis300]

it's not really low though, just not normal height.

I think this is key.

When loading down a traditional suspension car, we wouldn't think twice about the car squatting down.

AHC will also work like this when outside of it's constant height weight carrying capabilities.

 

[agaisin]

see my post here:
https://forum.ih8mud.com/100-series-cruisers/455099-signs-ahc-going.html#post6320507

See the section "Starting and Driving" about AHC in your owners manual:

"The vehicle height cannot be raised if the vehicle load exceeds the following limits:
- up to 4 occupants [150lb per person] plus about 660 lb in normal mode
- up to 4 occupants plus about 375 lb in the high mode

If the above load capacity is exceeded, the desired vehicle height may not be obtained even if the height select switch is pushed. (If the vehicle height cannot be raised in the normal mode and the height control indicator indicates "LO", this is because the vehicle is loaded too heavily. Under these conditions, drive your vehicle with due care.)

If the vehicle height cannot be raised even after unloading, push the height select switch on the "down arrow" side and then on the "up arrow" side. If this does not work, turn off the ignition once and then turn on. Operate the select switch again.
"

two additional points:
1) it doesn't say it's completely fine to drive that way - yes it's by design (more like a design constraint) but it also says "under these conditions drive with due care".

2) regarding overheating the system does have a lot of fluid but it doesn't exactly circulate that i know of so I'm not sure how much the overall system volume helps? The damping force actuators do have heat dissipating fins though.

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[1meancruiser]

I appreciate all the feedback. The jerking motion of the lowering when i stopped and the car staying in low when i started driving is what gave me doubts.


I'm gathering that this is normal.

Any thoughts on the AHC's exposure to heat. It seems counter productive to put the booster next to the exhaust manifold (not that there is anywhere else to put it) then to round them off the fluid tuing into a coil shape, i would think to assist with cooling, but given it's sitting right next to the exhaust it should just help in heating up the AHC fluid? wouldn't a heatshield with some heat reflective material be an obvious mod?

any thought?

 

[TeCKis300]

Were you on a grade when you stopped the car?

I've noticed with certain borderline heavy loads, that if I'm on a incline and where more of the weight is on one axle, that AHC may refuse to go to high. Then once I'm on level ground again, it will let me go into high without issue, and keep it in high for the next grade.

 

[1meancruiser]

No, it was level ground. Pulled off into the shoulder then back on.

 

[1meancruiser]

Guys, i'm a little dissapointed in the system being so weight sensative. I bought the 2006 around 4 months ago for the specific reason of having the AHC. A good mix of on road for my wife and off road for my outings. My prior car was a Land rover with solid axels and traditional suspension. When i bought this car, i specifically avoided land rovers for their air suspension knowing the reliability issues which come up. I thought the hydralic system would be much more reliable.

I'm a bit concerned about have 600-900lbs in the car and hitting a long distance trail. I know the car's capibility is 1500lbs, i thought anything less would be a non issue.

Can any of you give me real work experience on going on trails, long distance, with decent amount of weight in the car, and how the AHC has held up?

 

[Kigiin]

I have over 170K miles on mine and about 50K miles since adding bumpers, winch, rack, drawers, and 45 gallon aux fuel tank. With all of that plus 25 more gallons of fuel in jerry cans and fully loaded with gear, I haven't had any problems on or off road. I don't seriously off road with all that fuel, but everything else is there and I haven't had a problem on diificult trails.

Even without the fuel and gear with just me in the truck (I weight 240), I have the truck weighed on a scale at ~7,600lbs. Partially and fully loaded the truck does ride in L, but like I said it's not really low. And partially loaded it will stay in N but not go in H. All in all, it's doing the job.

 

[agaisin]

I have over 170K miles on mine and about 50K miles since adding bumpers, winch, rack, drawers, and 45 gallon aux fuel tank. With all of that plus 25 more gallons of fuel in jerry cans and fully loaded with gear, I haven't had any problems on or off road. I don't seriously off road with all that fuel, but everything else is there and I haven't had a problem on diificult trails.

Even without the fuel and gear with just me in the truck (I weight 240), I have the truck weighed on a scale at ~7,600lbs. Partially and fully loaded the truck does ride in L, but like I said it's not really low. And partially loaded it will stay in N but not go in H. All in all, it's doing the job.

i think it's fair to say you are outside the design parameters - you happen to be ok with the failsafe mode and more power to ya. however without other (unofficial) mods like stiffer tbars, stiffer springs, airbags and aftermarket (or tampered) globes with higher pressure and/or more volume, your system is basically in a form of limp mode if it's stuck in L or can't raise to H.

If you plan to load the vehicle with more weight than it's designed to handle you can either live with 'limp mode', mod the system to account for the weight increase (tbars springs airbags and maybe globe mods), or you can tear out ahc and go for the conventional suspension.

just my .02.

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[1meancruiser]

Thanks guys. great responses. My plan was to keep it relatively stock untill the 100k anniversary then get a little more serious...

Looks like i'll keep those plans.

 

[arbetrader]

i think it's fair to say you are outside the design parameters - you happen to be ok with the failsafe mode and more power to ya. however without other (unofficial) mods like stiffer tbars, stiffer springs, airbags and aftermarket (or tampered) globes with higher pressure and/or more volume, your system is basically in a form of limp mode if it's stuck in L or can't raise to H.

If you plan to load the vehicle with more weight than it's designed to handle you can either live with 'limp mode', mod the system to account for the weight increase (tbars springs airbags and maybe globe mods), or you can tear out ahc and go for the conventional suspension.

just my .02.

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If 800lbs was beyond the vehicle's designed systems, Toyota never would have rated the vehicle for a 1400lb payload. Just my .02

 

[agaisin]

If 800lbs was beyond the vehicle's designed systems, Toyota never would have rated the vehicle for a 1400lb payload. Just my .02

I'm not caught up on 800lbs, I'm just pointing out that if someone's loaded up the vehicle to the point where ahc system can't maintain proper height he has exceeded the load capacity (given the system functions fine under normal operating conditions). I'm pretty sure it had to be more than 800lbs to be in that situation unless his springs and tbs are tired and aren't carrying their weight but even so - if the system can't get out of L something is wrong. yes it can be driven "with due care" but it's not designed to be driven that way all the time. granted it seems like there's a difference b/w stuck in full low and overloaded Low (got as high as it could and then gave up - not low but not n) but either way it's not able to maintain n height...

Where did you get the 1400? from what i quoted in the owners manual it was 4x150 + 'about' 660 = 1260lbs where by design it can't be raised in normal mode, and 4x375=1500 where it can't be raised in high mode and the manual is clear that if your height can't be raised in normal and you're stuck in low you have exceeded the load capacity and should drive with due care.

here it is again:
"The vehicle height cannot be raised if the vehicle load exceeds the following limits:
- up to 4 occupants [150lb per person] plus about 660 lb in normal mode
- up to 4 occupants plus about 375 lb in the high mode

If the above load capacity is exceeded, the desired vehicle height may not be obtained even if the height select switch is pushed. (If the vehicle height cannot be raised in the normal mode and the height control indicator indicates "LO", this is because the vehicle is loaded too heavily. Under these conditions, drive your vehicle with due care.)"

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[arbetrader]

Curb weight is 5425, gvw is 6925 so payload would be 1500lb. I don't have an 06 myself,I just pulled those numbers from the web, but that's the rating.

 

[r3run33]

Hello my $.02 input in 2006 toyota began using "out source parts" for the AHC; for our year 2006 actually has a TSB put out. With your low miles, you may want to check to see if it was done. I had trouble with mine and had it switched out under warranty but now that I am out of warranty its coming out. I have a 2006 LX470 and did some research back then when I had lots of trouble. Denso did not make the OME parts when our vehicles where made. Now I'm not sure if the TSB used different parts but I will say after my system was fixed I did not have the same issues.