AHC please help

[SaadUK]

Hi guys I need some help urgently. I have recently changed complete suspension parts ie accumulators , spheres with cylinders, motors and shocks and springs. I followed instruction on how to introduce oil to the system and bleedin. On first few bleeds the oil was milky but after few more tries it slowly turned back to oil with very very few bubbles.

The problem is the ride is not bouncy but harsh. It looks like the AHC is not usin any force or damping and the road irregularities are directly felt in the cabin. Everything rattles.

I have scanned the AHC for fault codes but couldn't find any.

Please suggest what to do. Thanks.

 

[jOnathN]

More info needed:

Is it sitting at the correct height?
Is it hitting very hard over both small bumps and large or only one or the other?
I have not replaced the shocks before so this may be off base but: were there any plugs, caps, or seals left on the shocks that need to come off?
Will it raise and lower with the buttons inside?
Did you bleed the new shocks?
Did you bleed the main accumulator(the cylindrical one on the frame rail between front and rear actuators)?
Is there enough fluid in the system?


I would guess there is a shock install problem. If there are new globes installed, there is enough fluid, and the lines are connected properly then the ride should be acceptable even if nothing else is working...that part of the system is pretty simple. However if the shocks are not properly connected to the globes then it would ride very hard. 'Not properly connected' could mean not enough fluid or a blocked line/fitting; i am not sure what else.

 

[agaisin]

how did you scan for codes? ie you won't see any ahc codes using a typical obd scanner.

did you check your neutral pressure? even if the system is working perfectly, if your neutral pressure is sky high it'll be a stiff ride.

if you're not getting damping i'd look at either your damping force actuators (not the globes but the piece the globes screw into) or your damping switch.

if you dont already have the fsm i'd start looking there at the diagnostic procedures - might be time to check each part of the system methodically.

Sent from my iPhone using IH8MUD

 

[jOnathN]

Art,

I was thinking through possible causes for your paragraph 2 and 3.

I am only thinking of a few causes for high neutral pressure: height set much too high or vehicle weight much too high...both easily checked. Anything else come to mind?

Ditto for damping: unless broken or installed wrong (can't figure out how but probably some way) the actuators cannot eliminate the hydraulic path for damping. They can vary the orifice size (therefore damping) but there is no "block" state that would separate the globes from circuit. I.e. Even if the damping switch is not working and the actuator is stuck the damping should be no worse than the 'max damping' setting (step 16?)...which is firm but not harsh. Maybe his description is exaggerated?

However given that a lot was replaced this opens up the possibility of whole system install problems. E.g. Packaging plugs left in place, electrical connectors left undone, lines/elements not bled or purged right, etc.

 

[agaisin]

Art,

I was thinking through possible causes for your paragraph 2 and 3.

I am only thinking of a few causes for high neutral pressure: height set much too high or vehicle weight much too high...both easily checked. Anything else come to mind?

Ditto for damping: unless broken or installed wrong (can't figure out how but probably some way) the actuators cannot eliminate the hydraulic path for damping. They can vary the orifice size (therefore damping) but there is no "block" state that would separate the globes from circuit. I.e. Even if the damping switch is not working and the actuator is stuck the damping should be no worse than the 'max damping' setting (step 16?)...which is firm but not harsh. Maybe his description is exaggerated?

However given that a lot was replaced this opens up the possibility of whole system install problems. E.g. Packaging plugs left in place, electrical connectors left undone, lines/elements not bled or purged right, etc.

Good points.

Regarding causes for neutral pressure to be high (in the front) - aside from too much weight or too much height, the other explanation I can think of is if the TBs. Basically either they're old and tired and abused or they removed and never adjusted properly. In other words if they were removed then it would require reading the NP to know how much to adjut them and if they weren't cranked at all then about all the weight is being supported by the accumulators with no (or almost no) help from the TBs. Would start with confirming height and weight for sure. Also depending on age and use, tbs could be super tired.

Regarding your point about max damping - point taken. But here's my only counterpoint there - there's 4 settings comfort, normal, sport 1 and sport 2 (don't remember the labels exactly), but there's actually 16 steps. Conceptually, I believe (iirc) setting to comfort gives the system all 16 steps on each actuator, setting to normal gives each corner 12 steps (let's call it 5-16), setting to sport 1 gives each corner 8 steps to work with (let's call it 9-16) and sport 2 gives each corner 4 steps to work with (13-16).

So when we set it to sport 2 - we're not really at step 16 on all 4 corners, we're normally probably on step 13. If the system were ALWAYS on step 16 on all four corners I think that would be stiffer than what we feel when it's on sport 2... Make sense?

Of course there are other parts of the suspension that I think could play a role in perception of harshness - tires, tire pressure, loose wheel bearings, etc...

 

[jOnathN]

Good points! Unfortunately without more info from the OP we cannot get very far.

 

[SaadUK]

More info needed:

Is it sitting at the correct height?
Is it hitting very hard over both small bumps and large or only one or the other?
I have not replaced the shocks before so this may be off base but: were there any plugs, caps, or seals left on the shocks that need to come off?
Will it raise and lower with the buttons inside?
Did you bleed the new shocks?
Did you bleed the main accumulator(the cylindrical one on the frame rail between front and rear actuators)?
Is there enough fluid in the system?

I would guess there is a shock install problem. If there are new globes installed, there is enough fluid, and the lines are connected properly then the ride should be acceptable even if nothing else is working...that part of the system is pretty simple. However if the shocks are not properly connected to the globes then it would ride very hard. 'Not properly connected' could mean not enough fluid or a blocked line/fitting; i am not sure what else.

Thanks for the reply. I don't know the proper way to measure the height from the looks of it it seems normal.

It's hitting hard at small bumps and not as smooth as it should be on hard bumps. There is no FLOATING Ride feel.

I didn't notice any bleeding valve on shocks

Yes it lowers and highers with shocks. It takes around 12 seconds to go from N to HI. And 10 sec from N to LO height.

Yes I bled that too

There is enough fluid in the system but the gradient marks between Hi and LO is no more than 7 marks hardly.

 

[SaadUK]

how did you scan for codes? ie you won't see any ahc codes using a typical obd scanner.

did you check your neutral pressure? even if the system is working perfectly, if your neutral pressure is sky high it'll be a stiff ride.

if you're not getting damping i'd look at either your damping force actuators (not the globes but the piece the globes screw into) or your damping switch.

if you dont already have the fsm i'd start looking there at the diagnostic procedures - might be time to check each part of the system methodically.

Sent from my iPhone using IH8MUD

I used Gscan tool. It shows complete sensor readings of AHC but couldn't find NEUTRAL pressure.

If you are mentioning those cylinders then I have replaced and installed them with new as well on all four sides.

 

[SaadUK]

Art,

I was thinking through possible causes for your paragraph 2 and 3.

I am only thinking of a few causes for high neutral pressure: height set much too high or vehicle weight much too high...both easily checked. Anything else come to mind?

Ditto for damping: unless broken or installed wrong (can't figure out how but probably some way) the actuators cannot eliminate the hydraulic path for damping. They can vary the orifice size (therefore damping) but there is no "block" state that would separate the globes from circuit. I.e. Even if the damping switch is not working and the actuator is stuck the damping should be no worse than the 'max damping' setting (step 16?)...which is firm but not harsh. Maybe his description is exaggerated?

However given that a lot was replaced this opens up the possibility of whole system install problems. E.g. Packaging plugs left in place, electrical connectors left undone, lines/elements not bled or purged right, etc.

Thanks for the reply. Well there r no trouble codes visible on scanners so can't say if that is electrical fault. According to scanner the damping button works.

 

[uHu]

It looks like the onlly thing missing in the diagnostics is to measure neutral pressure and height at all three levels. Both are explained in this forum somewhere.
This is assuming the 4 globes/spheres/accumulators are changed with new OEM units.

One interesting Q is: How many years has it been sitting on those springs? After 5 years the coils would be to weak and the TBs requiring a tightening, both giving a too high neutral pressure.

 

[jOnathN]

Saad,

Thanks for the additional details.

The symptoms you describe (hits hard on small bumps, ok but not great on large ones *and* only 7 gradation changes of fluid between high and low) are usually what happens when the four damping spheres are low. Normally if you replace the spheres you should see roughly 13 gradation changes (+/-).

When the spheres are running low then they will be partially filled with fluid even at the low suspension setting because they just don't have the pressure to fully expand. Then when pressure is further increased to raise the truck higher they fill to the remaining capacity. Ergo only a small change in fluid level at the tank. With properly charged (usually meaning new) spheres the high pressure keeps the spheres almost empty of fluid at low and they can accept more as the truck is raised so there is a larger change at the tank.

The rest of the system can affect ride quality as well but not as much. The system is essentially all hydraulic so you would next look for restrictions at the various fluid fittings e.g.: are the actuators stuck in a wrong position that restricts flow, are the shock ports and lines connected right, any bypass or press release valves not opening right so they restrict flow, etc. That does not sound like it is occurring.

Also note that the 'shocks' on the AHC are not really shock dampers like on a regular suspension, they are simply hydraulic rams. They pass the shock right on through to the Damping Spheres similar to a remote reservoir system (but adaptable and computer controlled). This means that replacing the spheres on these trucks is the same as replacing shocks on a standard car (but easier on ours). Unless they are leaking fluid the actual shock rams should not ever need replacing.

The raise and lower times seem about right; maybe a little slow but not much. Toyota designed the system for durability and comfort so it moves slow and smooth rather than rapidly like one of the competition hydro cars that hop Anyway, if your times up and down were ridiculously long then that would suggest a problem with the central (main) accumulator cylinder or the pump system somewhere. Yours is probably fine.

On net this raises question about your spheres:
1) Did you use factory new damping spheres? Is it possible that someone swapped in used ones and thought you might not notice or did you use a set from a breaker maybe?
2) Are you sure they were actually replaced? I.e. maybe the shocks were replaced but not the spheres or the actuators were replaced but not the spheres?
3) Did you use LHM+ or Toyota AHC fluid to refill the system? My thinking here is that *if* you used brake fluid or something else by accident that it might dissolve the diaphragms after a few weeks causing the globes to fail. This takes a little time though so it would not likely show immediately

Or, as Art (agaisin) mentioned earlier, is the truck *really* overweight? If it is either overweight or jacked up too high the new spheres might behave like old ones because of massive overloading. I doubt this is the case for you since you have not mentioned anything about having an extra 500 kilos of static load =)

First thoughts. I'll see if I can think of alternate explanations.

 

[SaadUK]

Saad,

Thanks for the additional details.

The symptoms you describe (hits hard on small bumps, ok but not great on large ones *and* only 7 gradation changes of fluid between high and low) are usually what happens when the four damping spheres are low. Normally if you replace the spheres you should see roughly 13 gradation changes (+/-).

When the spheres are running low then they will be partially filled with fluid even at the low suspension setting because they just don't have the pressure to fully expand. Then when pressure is further increased to raise the truck higher they fill to the remaining capacity. Ergo only a small change in fluid level at the tank. With properly charged (usually meaning new) spheres the high pressure keeps the spheres almost empty of fluid at low and they can accept more as the truck is raised so there is a larger change at the tank.

The rest of the system can affect ride quality as well but not as much. The system is essentially all hydraulic so you would next look for restrictions at the various fluid fittings e.g.: are the actuators stuck in a wrong position that restricts flow, are the shock ports and lines connected right, any bypass or press release valves not opening right so they restrict flow, etc. That does not sound like it is occurring.

Also note that the 'shocks' on the AHC are not really shock dampers like on a regular suspension, they are simply hydraulic rams. They pass the shock right on through to the Damping Spheres similar to a remote reservoir system (but adaptable and computer controlled). This means that replacing the spheres on these trucks is the same as replacing shocks on a standard car (but easier on ours). Unless they are leaking fluid the actual shock rams should not ever need replacing.

The raise and lower times seem about right; maybe a little slow but not much. Toyota designed the system for durability and comfort so it moves slow and smooth rather than rapidly like one of the competition hydro cars that hop Anyway, if your times up and down were ridiculously long then that would suggest a problem with the central (main) accumulator cylinder or the pump system somewhere. Yours is probably fine.

On net this raises question about your spheres:
1) Did you use factory new damping spheres? Is it possible that someone swapped in used ones and thought you might not notice or did you use a set from a breaker maybe?
2) Are you sure they were actually replaced? I.e. maybe the shocks were replaced but not the spheres or the actuators were replaced but not the spheres?
3) Did you use LHM+ or Toyota AHC fluid to refill the system? My thinking here is that *if* you used brake fluid or something else by accident that it might dissolve the diaphragms after a few weeks causing the globes to fail. This takes a little time though so it would not likely show immediately

Or, as Art (agaisin) mentioned earlier, is the truck *really* overweight? If it is either overweight or jacked up too high the new spheres might behave like old ones because of massive overloading. I doubt this is the case for you since you have not mentioned anything about having an extra 500 kilos of static load =)

First thoughts. I'll see if I can think of alternate explanations.

Im thankful to all of my friends who helped in this issue especially Jonathan for all the detailed replies. Day before yesterday I bled the system again with complete new fluid and after a day of driving I felt drastic change in ride quality. Today I measured the gradients on reservoir and noticed it increased from 7 to roughly 11 marks. Maybe it will get 13 + after some more circulation. But the ride is silk as it should be. All I feel is little tyre feed back but that's fine as the tyres are manufactured in 2010 and the car was parked most of the time. Rim size is also 18. I changed everything at home and there was no workshop involved. Everything was bought by my self from authorised Toyota dealer except oil. What I noticed was the old oil in the systems viscosity was very thin even though i put it in the car few weeks back. Maybe the oil was non original.

Thank you all again. God bless.

 

[jOnathN]

Great! Glad it worked out and without replacing anything else.

 

[yuji]

Im thankful to all of my friends who helped in this issue especially Jonathan for all the detailed replies. Day before yesterday I bled the system again with complete new fluid and after a day of driving I felt drastic change in ride quality. Today I measured the gradients on reservoir and noticed it increased from 7 to roughly 11 marks. Maybe it will get 13 + after some more circulation. But the ride is silk as it should be. All I feel is little tyre feed back but that's fine as the tyres are manufactured in 2010 and the car was parked most of the time. Rim size is also 18. I changed everything at home and there was no workshop involved. Everything was bought by my self from authorised Toyota dealer except oil. What I noticed was the old oil in the systems viscosity was very thin even though i put it in the car few weeks back. Maybe the oil was non original.

Thank you all again. God bless.

Congrats and thanks for the info in your post! It's super useful. After AHC fluid change at the stealership, I'm getting less graduations too.

I am having doubts about my AHC too - I don't have a baseline to compare to but a subjective previous test drive in a different vehicle.

Enjoy the ride!