Air suspension question

[Amazo]

Hi all.

I think this will be a simple question for those more experienced than me.

The car is a 2004 100 series with AHC.

I have a clear oil dripping from the bottom of my rear right shock absorber. My understanding is that the shock should be filled with nitrogen.

As it is dripping oil, is it likely that an accumulator (sphere) has failed and the AHC fluid has been pumped into the shock absorber and burst a seal?

Cheers,
Gary.

 

[Rhetoric]

Hi all.

I think this will be a simple question for those more experienced than me.

The car is a 2004 100 series with AHC.

I have a clear oil dripping from the bottom of my rear right shock absorber. My understanding is that the shock should be filled with nitrogen.

As it is dripping oil, is it likely that an accumulator (sphere) has failed and the AHC fluid has been pumped into the shock absorber and burst a seal?

Cheers,
Gary.

The shock is filled with fluid. Only the accumulator (globes) have nitrogen in them.

Where on the shock is the leak? How rusty is your truck?

 

[Amazo]

The shock is filled with fluid. Only the accumulator (globes) have nitrogen in them.

Where on the shock is the leak? How rusty is your truck?

The leak is coming from under the shroud. No oil on the shroud itself.

The truck is not rusty at all.

So the system is oil from reservoir to globe, then nitrogen in the globe, then more oil between the globe and shock?

For 3 mornings in a row the back of the car was very low. It pumped up when the engine was started and operated as normal during each day.

On the third day I discovered the leak, so I've parked the truck up. That was four days ago, and it is still sitting at normal ride height. Why has it not dropped overnight like it did before? I'm puzzled.

I have it booked in for new shocks, but I'm just trying to understand how the system works.

 

[Jack90210]

It's quite likely that the only problem is sagged springs and/or more load in the car than it is designed to handle. The problem having "fixed itself" makes this seem even more likely.

Measuring the front and rear pressures should be one of the first steps, whether it's done by you or the technician. A common "fix" for weeping or leaky shocks is replacement, when it's simply a symptom of higher-than-spec pressures due to the springs and/or torsion bars not carrying enough of the weight.

The ABCs of AHC - How to Measure, Flush, and Adjust all in one place

forum.ih8mud.com

 

[Amazo]

It's quite likely that the only problem is sagged springs and/or more load in the car than it is designed to handle. The problem having "fixed itself" makes this seem even more likely.

Measuring the front and rear pressures should be one of the first steps, whether it's done by you or the technician. A common "fix" for weeping or leaky shocks is replacement, when it's simply a symptom of higher-than-spec pressures due to the springs and/or torsion bars not carrying enough of the weight.

The ABCs of AHC - How to Measure, Flush, and Adjust all in one place

forum.ih8mud.com

Thanks for that extra info.

I'll pass that on to my mechanic.

Shouldn't be the rear springs as they are genuine Toyota springs with just 10,000 miles on them with zero load in the boot. Torsion bars are likely to be the originals.

Thanks again.

 

[Amazo]

It's quite likely that the only problem is sagged springs and/or more load in the car than it is designed to handle. The problem having "fixed itself" makes this seem even more likely.

Measuring the front and rear pressures should be one of the first steps, whether it's done by you or the technician. A common "fix" for weeping or leaky shocks is replacement, when it's simply a symptom of higher-than-spec pressures due to the springs and/or torsion bars not carrying enough of the weight.

The ABCs of AHC - How to Measure, Flush, and Adjust all in one place

forum.ih8mud.com

I've now left the truck for another week, and it is still sitting at normal ride height. I'm really struggling to understand how this can be down to saggy springs.

There is no AHC fluid visible in the reservoir under the bonnet. So what's helping the springs keep the rear of the car up? It can only be the rear shocks as far as I can tell. This means the rear right shock (the leaking one) must have resealed somehow, which would seem impossible to me.

I'm very tempted to top up the AHC fluid and drive it around a bit to see what happens.

It was only a few weeks back that I was telling a friend how marvelous my AHC suspension is

 

[David310]

Have you taken pressure readings yet? What is your ride height set to measuring center of wheel to bottom edge of fender? What are the part numbers for your new springs?

Excessive pressure will cause shocks to weep. Normal for the rears to weep when overloaded such as when towing with heavy tongue weight + gear in the back and family on board.

 

[suprarx7nut]

You should absolutely refill your fluid reservoir. You do not want to suck in air. If you use plastic bottles, strain the fluid to ensure you don't gel the pump with slime (manufacturing defect from 2020~2021).

I bet you have a leak. Perhaps it's intermittent.

If you haven't checked pressures, you should, but that should create a drooping effect after sitting. That's likely a failed seal on a shock or hydraulic line. If you're on the east coast, rust is a likely contributor.

 

[GremlinMobile]

You should absolutely refill your fluid reservoir. You do not want to suck in air. If you use plastic bottles, strain the fluid to ensure you don't gel the pump with slime (manufacturing defect from 2020~2021).

I bet you have a leak. Perhaps it's intermittent.

If you haven't checked pressures, you should, but that should create a drooping effect after sitting. That's likely a failed seal on a shock or hydraulic line. If you're on the east coast, rust is a likely contributor.

I second that advice. That plastic fluid messed up my AHC pump. Local dealer quoted me 20-30k to redo the AHC system to fix it. Ended up taking apart the pump to clean it myself and was back in business. Just re-used the gelled fluid after straining it through coffee filter. Long story short, use new fluid from steel can.

 

[J1000]

From the coast in the UK and says his truck is "not rusty at all." Yeah right

Just kidding. Firstly, they aren't shocks in the rear, they are just hydraulic rams. This is the key to understanding how the AHC system works. What looks like shock absorbers on each suspension corner are simply rams. All they do is transfer the vertical movement into the hydraulic system which then is pushed on by the globes.

Possibly your globes have failed or have started to leak, but you can't know until you check with Techstream. They are affordable and replacement is really easy, same with the AHC pump.

If the rear rams are leaking at the top that can be caused by 2 things usually:

1. The most common is temporary: fluid pushing past the cylinders in the hydraulic ram. This is actually a safety feature, like an over-pressure valve. The fix is to check the pressures on all 4 corners and adjust as necessary. If it has had a chronic leak because it was sitting on old springs for too long then the seals could be gone, maybe...I am not sure about that.

2. Rust/deterioration/damage of the metal AHC lines or cylinder itself. Fix is to replace the damaged parts which is almost impossible without lifting the body off the chassis.

 

[Amazo]

From the coast in the UK and says his truck is "not rusty at all." Yeah right

Just kidding. Firstly, they aren't shocks in the rear, they are just hydraulic rams. This is the key to understanding how the AHC system works. What looks like shock absorbers on each suspension corner are simply rams. All they do is transfer the vertical movement into the hydraulic system which then is pushed on by the globes.

Possibly your globes have failed or have started to leak, but you can't know until you check with Techstream. They are affordable and replacement is really easy, same with the AHC pump.

If the rear rams are leaking at the top that can be caused by 2 things usually:

1. The most common is temporary: fluid pushing past the cylinders in the hydraulic ram. This is actually a safety feature, like an over-pressure valve. The fix is to check the pressures on all 4 corners and adjust as necessary. If it has had a chronic leak because it was sitting on old springs for too long then the seals could be gone, maybe...I am not sure about that.

2. Rust/deterioration/damage of the metal AHC lines or cylinder itself. Fix is to replace the damaged parts which is almost impossible without lifting the body off the chassis.

Have you taken pressure readings yet? What is your ride height set to measuring center of wheel to bottom edge of fender? What are the part numbers for your new springs?

Excessive pressure will cause shocks to weep. Normal for the rears to weep when overloaded such as when towing with heavy tongue weight + gear in the back and family on board.

No pressure readings taken. As mentioned in my earlier post, I'm just trying to understand how the system works, as this will help me in making a decision whether to go for a conversion or get the existing system fixed. I'm not doing the work myself. An injury prevents me from doing that. I've done most of the work in the past, but not now

The truck has never been overloaded, and has never towed anything heavy. It's also never been off road, so it's had an easy life. The right rear shock (ram) cannot be described as weeping. It went from nothing to running out overnight, leaving a small puddle everywhere I stopped. So it would appear the shock has blown a seal.

 

[Amazo]

You should absolutely refill your fluid reservoir. You do not want to suck in air. If you use plastic bottles, strain the fluid to ensure you don't gel the pump with slime (manufacturing defect from 2020~2021).

I bet you have a leak. Perhaps it's intermittent.

If you haven't checked pressures, you should, but that should create a drooping effect after sitting. That's likely a failed seal on a shock or hydraulic line. If you're on the east coast, rust is a likely contributor.

I will refill the reservoir, and thanks for the advice regarding the fluid. I've not heard of that issue before. However, I will be driving it 10 miles to the garage where a conversion to conventional shocks and springs will take place. I refill the fluid so as not to stuff the pump up, just in case someone wants to return it to AHC in the future.

No rust on top or underneath this truck. It has had a blessed life. It's first thirteen winters were spent in a temperature controlled garage in Marbella. It was the first owners "bus" to take his family and a small trailer from the UK to Marbella, and was parked up once it got there, as he then used his rather more expensive car to travel around. The next 6 UK winters that I have subjected it to have had no visible effect underneath. It's still running it's original Toyota exhaust, albeit with a tiny hole in the rear box.

 

[Amazo]

From the coast in the UK and says his truck is "not rusty at all." Yeah right

Just kidding. Firstly, they aren't shocks in the rear, they are just hydraulic rams. This is the key to understanding how the AHC system works. What looks like shock absorbers on each suspension corner are simply rams. All they do is transfer the vertical movement into the hydraulic system which then is pushed on by the globes.

Possibly your globes have failed or have started to leak, but you can't know until you check with Techstream. They are affordable and replacement is really easy, same with the AHC pump.

If the rear rams are leaking at the top that can be caused by 2 things usually:

1. The most common is temporary: fluid pushing past the cylinders in the hydraulic ram. This is actually a safety feature, like an over-pressure valve. The fix is to check the pressures on all 4 corners and adjust as necessary. If it has had a chronic leak because it was sitting on old springs for too long then the seals could be gone, maybe...I am not sure about that.

2. Rust/deterioration/damage of the metal AHC lines or cylinder itself. Fix is to replace the damaged parts which is almost impossible without lifting the body off the chassis.

I promise, it's not rusty at all. Explanation in previous post. The shocks (rams) themselves have what looks like surface rust on the shrouds, and if my memory serves correctly, the linkages in the AHC height adjusters have surface rust on. But the truck has never seen a welding torch and hopefully will not for a number of years to come.

Thank-you for the explanation regarding the rams (not shocks). This has completed the picture for me as to how the system works, and has helped me make the decision to go for a conversion to new springs/torsion bars and conventional shocks. I think at 20 years of age, I don't want to risk more failures on the AHC system.

Thanks to everyone for your input. I feel I understand the system now, and I'm psyching up for the relatively rough ride I'll undoubtedly get once converted.

Cheers.

 

[Amazo]

From the coast in the UK and says his truck is "not rusty at all." Yeah right

Just kidding. Firstly, they aren't shocks in the rear, they are just hydraulic rams. This is the key to understanding how the AHC system works. What looks like shock absorbers on each suspension corner are simply rams. All they do is transfer the vertical movement into the hydraulic system which then is pushed on by the globes.

Possibly your globes have failed or have started to leak, but you can't know until you check with Techstream. They are affordable and replacement is really easy, same with the AHC pump.

If the rear rams are leaking at the top that can be caused by 2 things usually:

1. The most common is temporary: fluid pushing past the cylinders in the hydraulic ram. This is actually a safety feature, like an over-pressure valve. The fix is to check the pressures on all 4 corners and adjust as necessary. If it has had a chronic leak because it was sitting on old springs for too long then the seals could be gone, maybe...I am not sure about that.

2. Rust/deterioration/damage of the metal AHC lines or cylinder itself. Fix is to replace the damaged parts which is almost impossible without lifting the body off the chassis.

Forgot to mention that buying a car from a coastal town in the UK isn't really an issue nowadays. People just don't consider it a problem anymore. The rust proofing is so good now, unlike 40 years ago when coastal cars were definitely avoided

 

[Rhetoric]

If you understood the system you’d make the simple repair and enjoy it. Not trash it for what will be a very sub par experience.

Its nearly impossible to “go back to AHC” once a shop guts it.

 

[Amazo]

If you understood the system you’d make the simple repair and enjoy it. Not trash it for what will be a very sub par experience.

Its nearly impossible to “go back to AHC” once a shop guts it.

I definitely understand the system now, because of the input I've received on this thread, and it's that understanding that has lead me to want a different "experience". An experience that doesn't involve worrying about the next expensive repair to the AHC system. I cannot do the fixes myself nowadays due to an injury, so I have to pay people to do them.

Another point is that pretty much all my journeys are local at 30mph and under. At that speed my air suspension does not work very well at all, especially on small sharp edged bumps, and there are loads of them around here. Even after having all the globes changed at Plaeides, and fitting genuine Toyota (purple paint) rear springs 6 years ago, the ride did not get any better at low speeds on bumpy roads.

My father's new air suspension Mercedes is exactly the same, it cannot cope well with the small stuff. Both are beautiful on the open road at 50mph plus, but I rarely use the main roads. So my ride experience may not be any worse than it is now. Might even be better, who knows?

Also, from what I understand, the AHC will not be gutted. It will be left in place for a future owner to return to AHC should they wish to. The pipes will be cut and capped at each corner. The globes and all pipework will be left in place. The part I don't know about is the pump. I don't know if this is electrically or mechanically driven, and what happens to it if left in place. If electric, I guess it'll be switched off, if mechanical, I'm relying on my chosen garage to know what to do. He is experienced in the AHC system on Landcruisers.

Thanks again for your input.

 

[J1000]

If you cut the pipes it's pretty much done because it's inaccessible in the rear without lifting the body off the chassis. Many have gone before you and regretted it.

Again, it's not air suspension.

 

[Amazo]

If you cut the pipes it's pretty much done because it's inaccessible in the rear without lifting the body off the chassis. Many have gone before you and regretted it.

Again, it's not air suspension.

In that case, I won't suggest to the next owner that it can be easily converted back to AHC. I'd like to be able to say that, as I've seen a few adverts in the past that say exactly that, but if what you say is true, then I won't say it. I will talk to my mechanic about it, he will know for certain.

I will report back here shortly after the conversion (15-8-24) with a totally honest opinion on whether I regret this decision or not. I've nothing to hide. If it turns out to be a poor choice I will say so. I'm not one for fibbing

My apologies for saying air suspension when it's not. It must be annoying for some.

 

[GremlinMobile]

If you cut the pipes it's pretty much done because it's inaccessible in the rear without lifting the body off the chassis. Many have gone before you and regretted it.

Again, it's not air suspension.

Just out of curiosity, would it be possible to route a new AHC fluid pipe or hose in a more accessible route? As these things age, seems like getting the pre-bent pipes, and fitting them, is becoming harder. Hydraulic shops make up hoses with custom fittings all the time. Has anyone done this? If you can zip tie the hose on the inside of the frame, maybe that'll be just good enough in a lot of cases?

 

[Amazo]

Just out of curiosity, would it be possible to route a new AHC fluid pipe or hose in a more accessible route? As these things age, seems like getting the pre-bent pipes, and fitting them, is becoming harder. Hydraulic shops make up hoses with custom fittings all the time. Has anyone done this? If you can zip tie the hose on the inside of the frame, maybe that'll be just good enough in a lot of cases?

From what J1000 said, I'm guessing it might be tricky to get a pipe to the rear rams if it's that tight up there. The original route might be the only practical way

Someone else will know more for sure.