Props to PADDO's AHC fluid replacement method! (1 Viewer)
- Thread starter Clunky
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Thanks, happy you got some value out of my musings. Being such an “old” system you’re not likely to find many youngish mechanics that have had any training on this system, or for that matter, anyone prepared to spend some time on diagnostics.
SgtMoonracer
SILVER Star
Just a Reader's Digest version of my experience... When I scheduled my '05 LX at the dealer this year for the airbag recall, I called and asked about having the AHC flushed. The dealership representative, who told me that he had been there over 20 years, had never heard of such a thing... told me: "you're not supposed to change that fluid"(!!!) He did eventually quote me a price of just over $200, and I told them to go ahead and do it while they had it in the shop. Ten minutes later he called me back in a panic, and told me the fluid was way more expensive than he thought, and it was going to be over $400. I told them to forget it. Thankfully I do most of my own work, and shouldn't have to use them for anything, but it's frightening that the only dealership local to me has no knowledge of this procedure.
I bought a 2.5 liter can of fluid and used Paddo's method last week. My reservoir was a little low to start with. Both rear drains had either been monkeyed with, or had partially been dissolved by road salt (welcome to PA), so I could not get a wrench to fit on them. I finally got a set of vice grips on the driver's side, and it opened right up, but spewed fluid everywhere since I couldn't get the tubing on the fitting.
I ended up draining 2 liters of fluid. As you can see from the attached picture, it was probably a little bit overdue.
Thanks again Paddo, for a great write-up.
I bought a 2.5 liter can of fluid and used Paddo's method last week. My reservoir was a little low to start with. Both rear drains had either been monkeyed with, or had partially been dissolved by road salt (welcome to PA), so I could not get a wrench to fit on them. I finally got a set of vice grips on the driver's side, and it opened right up, but spewed fluid everywhere since I couldn't get the tubing on the fitting.
I ended up draining 2 liters of fluid. As you can see from the attached picture, it was probably a little bit overdue.
Thanks again Paddo, for a great write-up.
I also asked my local Toyota dealership for a quote to do this on my LX. I had to ask three separate times while my truck was in for unrelated work. Finally the rep at the desk told me he talked to their master mechanic about it and was informed this wasn’t necessary. ‘It’s a closed system, shouldn’t ever need any maintenance.’ I mentioned that Toyota lists it in their recommended service intervals and he said that’s probably precautionary for legal reasons but that they’ve never done this work. I said thanks and went home to find this thread. I suspect the fluid’s never been looked at in 140k. I’ll get to it in the next couple weeks.
$400 quote, wow! That's BS!
PabloCruise
SILVER Star
Disappointing to hear these stories of dealership service for the AHC system...
You'll find them here.
Literally just finished this up. After seeing the above picture, I was pretty impressed that the fluid in the reservoir was just a dark brown, but what came out of the accumulator and the globes was darker with a lot of black sediment settling at the bottom. Is that telling of failing seals or anything? It came out freely and plentifully from each spot, but I pulled nearly .7 L from the rear DS globe alone. Is *that* bad??
Either way, another big thanks to @PADDO for putting this together, and being the resident AHC specialist!
Either way, another big thanks to @PADDO for putting this together, and being the resident AHC specialist!
How high was your rear endLiterally just finished this up. After seeing the above picture, I was pretty impressed that the fluid in the reservoir was just a dark brown, but what came out of the accumulator and the globes was darker with a lot of black sediment settling at the bottom. Is that telling of failing seals or anything? It came out freely and plentifully from each spot, but I pulled nearly .7 L from the rear DS globe alone. Is *that* bad??
Either way, another big thanks to @PADDO for putting this together, and being the resident AHC specialist!
when you drain from one damper assembly you’re actually getting fluid from both shock actuators and both damper accumulators on that circuit, either front or rear as they are connected. That’s why either the front or rear drops to the bump stops when bleeding. Getting 0.7L out could be due to extra height or highish rear neutral pressure (compressing more fluid into the accumulators) which is expelled as you reduce the pressure in the system by bleeding it down. If you get very little fluid out, from a normal height and normal neutral pressure, it suggests your damper accumulators have very little or no charge left. The design of the system has what we’d call “dead legs” with the shock actuators being at the extremities of the system with just one port in/out. The fluid doesn’t recirculate so contaminates can tend to build up at the extremities as they aren’t readily carried back to tank where’d they’d settle as a sludge on the bottom. That’s why just eyeballing the color of the fluid in the reservoir isn’t a great indicator of very much as the junk is at the ends of the system.Thanks Paddo! Any issues with swapping the bleeders as I work each corner? i.e. when the fluid stops flowing unscrew the old bleeder and install the new one?
So my modified procedure would look like this:
4. Starting at the height accumulator (12 inch long cylinder on DS outer frame rail, between front and rear damper assemblies) connect your drain tube, crack the bleeder and commence draining fluid, when fluid flow stops, remove and replace bleeder valve. You should drain ~0.3 liters.
5. Move to the front LH damper assembly, connect tube, crack the bleeder and drain until the front has dropped down to the bump stops. Both sides of the vehicle will lower together (because they are hydraulically connected) and you should drain ~0.4 liters. When fluid flow stops, remove and replace bleeder valve.
6. Same as 5 but at LH Rear
7. Making sure there is enough fluid in the reservoir, Bleed PS front valve and replace (should be a fairly small amount of fluid?).
8. After checking reservoir levels, Bleed PS Rear. Remove and replace valve (should be a fairly small amount of fluid?).
9. Start the vehicle, let it idle for 30-60 seconds and then press the UP button to raise to NORMAL height. The whole system will refill and recharge with new fluid from the reservoir and the level in the reservoir will be drawn down to slightly over the max line if everything has gone as expected.
10? Now would I have to go back and do quick bleeds on each side to get bubbles out because I Removed and replaced the valves or should it be ok?
11. You're done, confirm that the reservoir fluid level is correct - between max and min at N height with the engine running. There is nothing wrong with leaving the level slightly over the max line.
So my modified procedure would look like this:
4. Starting at the height accumulator (12 inch long cylinder on DS outer frame rail, between front and rear damper assemblies) connect your drain tube, crack the bleeder and commence draining fluid, when fluid flow stops, remove and replace bleeder valve. You should drain ~0.3 liters.
5. Move to the front LH damper assembly, connect tube, crack the bleeder and drain until the front has dropped down to the bump stops. Both sides of the vehicle will lower together (because they are hydraulically connected) and you should drain ~0.4 liters. When fluid flow stops, remove and replace bleeder valve.
6. Same as 5 but at LH Rear
7. Making sure there is enough fluid in the reservoir, Bleed PS front valve and replace (should be a fairly small amount of fluid?).
8. After checking reservoir levels, Bleed PS Rear. Remove and replace valve (should be a fairly small amount of fluid?).
9. Start the vehicle, let it idle for 30-60 seconds and then press the UP button to raise to NORMAL height. The whole system will refill and recharge with new fluid from the reservoir and the level in the reservoir will be drawn down to slightly over the max line if everything has gone as expected.
10? Now would I have to go back and do quick bleeds on each side to get bubbles out because I Removed and replaced the valves or should it be ok?
11. You're done, confirm that the reservoir fluid level is correct - between max and min at N height with the engine running. There is nothing wrong with leaving the level slightly over the max line.
You’ll be fine to replace the bleeders at each point as you’ve outlined. That’s what I’ve done, bleed, unscrew old and screw in new one. Don’t over tighten them, just firm them up and pop the rubber cap back on. I wouldn’t bother with Step 10 as long as you don’t wait forever to screw the new bleeder in. Probably wouldn’t hurt to check for any drips after you’ve recharged the system as the new bleeders might need a bit of encouragement (slightest tightening) to seat properly.
Thanks again to @PADDO! Did mine today. Easy job, don’t know why I kept putting it off. Valves were in good shape, no need for replacement. The turkey baster I bought was too fat to get to the bottom of the AHC reservoir but I got most of it. Fluid was pretty black out of the reservoir and a foamy black out of the shocks. For the craft beer fans, it looked like a stout poured from a nitro tap. I have pics of the fluid, but can’t figure out how to upload from my phone. I’ll edit this post next Monday to include them.
I don’t really notice a huge difference in ride quality but I am happy to have gotten this one checked off.
edit: Added pictures. The first is the reservoir fluid, the second picture (Pepsi bottle in foreground) is from the shocks and accumulator. When the fluid first came out it was sort of foamy, but it eventually settled down into what you see in the picture. Pretty nasty stuff compared to what I put in.
I don’t really notice a huge difference in ride quality but I am happy to have gotten this one checked off.
edit: Added pictures. The first is the reservoir fluid, the second picture (Pepsi bottle in foreground) is from the shocks and accumulator. When the fluid first came out it was sort of foamy, but it eventually settled down into what you see in the picture. Pretty nasty stuff compared to what I put in.
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Thanks @PADDO this worked great!
This project gave me yet another reason to pull the running boards but my family is still not convinced.
New to me 142k miles, dark ugly fluid came out. I assume the system’s never been touched. Reservoir was 2 ticks below Min mark even with AHC set to L. I drained a hair over 2 liters total. Now it sits at Min mark in N after exchange adding 2.5 liters. I bought five 1L bottles and I’ll repeat the process soon with the remaining 2.5L for even cleaner fluid.
I replaced the bleeders and caps though they were mostly in good condition. They were cheap and I’d ordered them ahead so I figured, why not swap in the new ones? I was prepared for the worst because it looked rusty under there but I had no trouble bleeding. I cracked all five before I started just to make sure I wouldn’t have trouble mid process.
Could be my imagination but it feels like it raises and lowers more smoothly and quickly now.
I’ve had Techstream for months but haven’t tracked down a pc yet (I wasn’t aware people still use these?). Next step will be to fire it up and set pressures/height with new springs.
Here are some photos with part numbers for those who follow:
This project gave me yet another reason to pull the running boards but my family is still not convinced.
New to me 142k miles, dark ugly fluid came out. I assume the system’s never been touched. Reservoir was 2 ticks below Min mark even with AHC set to L. I drained a hair over 2 liters total. Now it sits at Min mark in N after exchange adding 2.5 liters. I bought five 1L bottles and I’ll repeat the process soon with the remaining 2.5L for even cleaner fluid.
I replaced the bleeders and caps though they were mostly in good condition. They were cheap and I’d ordered them ahead so I figured, why not swap in the new ones? I was prepared for the worst because it looked rusty under there but I had no trouble bleeding. I cracked all five before I started just to make sure I wouldn’t have trouble mid process.
Could be my imagination but it feels like it raises and lowers more smoothly and quickly now.
I’ve had Techstream for months but haven’t tracked down a pc yet (I wasn’t aware people still use these?). Next step will be to fire it up and set pressures/height with new springs.
Here are some photos with part numbers for those who follow:
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Thank you for this thread and it worked like a charm as I just finished swapping out the fluid in my lx470 with 200k+ miles.
The fluid came out very milky... a neighbour commented that there’s probably water in the fluid. I let the fluid settle the fluid is a dark red and the milky substance seems to be sediment within the fluid. Anyone know why my fluid looks like this
The fluid came out very milky... a neighbour commented that there’s probably water in the fluid. I let the fluid settle the fluid is a dark red and the milky substance seems to be sediment within the fluid. Anyone know why my fluid looks like this
That image probably wins the prize for “worst looking fluid”. Who knows what’s been added previously. If you search the term “water reaction test” by me you’ll get images of what fresh fluid + distilled water looks like - as AHC fluid is lighter than water, has a very low affinity to water and there are no detergents you’ll get a distinct fluid/water boundary. You’ll also see what AHC fluid + brake fluid + water looks like in a test sample. As brake fluid has an affinity for water you’ll get a scum in solution and an unclear oil/water boundary. When you do a fluid changeout you still have a reasonable amount of fluid in the upper chamber of the “shocks” thats not expelled so it might be worth doing a follow up fluid change after that old milky stuff has had a chance to dilute into the fresh stuff. A simple field test to determine the presence of water in a hydraulic fluid sample, above about 400ppm, is what’s called the “crackle test” - you do that if you suspect the presence of water. You can also place a few drops of your sample into a jar of water to see if it clumps and floats or disperses which will show if detergents/surfactants are present. To me there’s no question that your sample is contaminated.
Thanks Paddo... Yeah I figured that there is contamination in the fluid and will be doing a follow up bleeding.
How long should I wait for to do the follow up bleed? I was thinking after a tank of gas around 300miles?
Also, should I be using the AHC more often just to get the fluid mixing a bit more?
At the follow up bleed, I presume I wouldn't need to take out the fluid in the reservoir if they don't look too bad. How much more fluid should I bleed out at the follow up bleed? Until clear?
Do you think this contaminated fluid would've done some irreversible damage to the AHC system? Any symptom I should look out for? The car rides just fine and I actually feel that the car lowers and raises quicker after the fluid exchange.
Sorry for the many questions... I still kinda new to my car. Thanks.
How long should I wait for to do the follow up bleed? I was thinking after a tank of gas around 300miles?
Also, should I be using the AHC more often just to get the fluid mixing a bit more?
At the follow up bleed, I presume I wouldn't need to take out the fluid in the reservoir if they don't look too bad. How much more fluid should I bleed out at the follow up bleed? Until clear?
Do you think this contaminated fluid would've done some irreversible damage to the AHC system? Any symptom I should look out for? The car rides just fine and I actually feel that the car lowers and raises quicker after the fluid exchange.
Sorry for the many questions... I still kinda new to my car. Thanks.
Just to verify even further how much confusion there is surrounding AHC...
Called local Toyota dealer (large dealer) to see if I could buy AHC. They don’t sell it and said they don’t flush it either. I asked what about the LC’s that have it. They said they are so rarely in there that they will “cross that bridge when the come to it” WTF!?!?
Called large Lexus dealer. First guy told me they don’t sell fluid because they have to buy in bulk, but I can pay for flush. Cost of flush $491!!! Spoke to another guy in service and he told me they have the 1 liter bottles of it that they will sell me for $16/bottle.
Planning to pick up 3 bottles sometime soon, but will believe it when I see it I guess!
PADDO: Thanks for the detailed info as it sounds like the labor is literally 10x’s the cost of the fluid at the dealer.
Called local Toyota dealer (large dealer) to see if I could buy AHC. They don’t sell it and said they don’t flush it either. I asked what about the LC’s that have it. They said they are so rarely in there that they will “cross that bridge when the come to it” WTF!?!?
Called large Lexus dealer. First guy told me they don’t sell fluid because they have to buy in bulk, but I can pay for flush. Cost of flush $491!!! Spoke to another guy in service and he told me they have the 1 liter bottles of it that they will sell me for $16/bottle.
Planning to pick up 3 bottles sometime soon, but will believe it when I see it I guess!
PADDO: Thanks for the detailed info as it sounds like the labor is literally 10x’s the cost of the fluid at the dealer.
