AHC Accumulator Bleed Valve -- broke off.

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mkivtdi

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Nov 14, 2016
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Hi all -- was preparing to bleed the AHC system on the car today...

I decided to start with the accumulator (driver's side between front and rear actuators) and, long story short, the nut was so rusted and seized on that the whole 'nipple' ripped off. (i tried Kroil, PB blaster, etc...)

So question #1: Why didn't AHC fluid start pouring out?!?

A sample from the AHC bottle and a little bleed at each corner shows golden/clean fluid. (is that the right color for this fluid? If so, I'll return the 2 cans of AHC I got from the Toyota dealer).


Thanks, and happy thanksgiving everyone!
 
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Fluid didn't come out because the bleeder screw's tapered seat is still "seated". Same design as a standard brake caliper bleed screw.
AHC fluid hasn't been golden/clear/straw colored for years. Pink/rose dye was added around 2008 or so to help avoid confusion with other clearish fluids like brake fluid.
 
mkivtdi said:
So then I should definitely flush it. Once I figure out my accumulator issue.
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If you're concerned with the fluid that's in your system you can do the water reactive test for brake fluid - search the term "reactive" in posts by me and you'll see how to do the test and how AHC fluid contaminated with brake fluid reacts to the test. Your height accumulator holds about 300ml when charged which is about 30% of the fluid within the system (not including reservoir) so it's desirable to fix the sheared bleeder so you can do proper fluid exchanges.
 
Now that I've baselined the rest of my car (tires, drivetrain fluids, brakes all around, etc) I've only got the AHC flush left to do...

So, any ideas on the best approach to removing the sheared off bleeder plug? How much pressure is behind that valve?

Also, any part number on its replacement? I can't really find much in any part diagrams.

https://forum.ih8mud.com/attachments/bleed-gif.36919/

All of the other bleed plugs on the accumulators cracked open easily. There's always one thing to turn a 1 hour job into an entire hassle. lol.
 
Hopefully @PADDO has an idea for replacement bleeder. If its a common size, most auto part stores carry them.

As for removing the twisted off bleeder, I would try to use an easy-out. Just be mindful to not go too deep with the drill or easy out as you can ruin the seat that the bleeder seals on. There's gonna be a little pressure behind the plug and fluid will come out, but just remember to swap in the new plug quickly and bleed the system well after that.
 
Over here, the ahc fluid is still straw colored.
If my memory serves me right, the bleeders are M7 (7 mm thread).
 
Just for hypothetical purposes, if I use an ezout and it suddenly unthreads and comes out, i'm not going to get blasted by tons of PSI of fluid, will I? There's one thing to slowly crack open a valve, and another trying to do it this way...

That's my only concern...

Thanks for all the info, all!
 
mkivtdi said:
Just for hypothetical purposes, if I use an ezout and it suddenly unthreads and comes out, i'm not going to get blasted by tons of PSI of fluid, will I? There's one thing to slowly crack open a valve, and another trying to do it this way...
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This is on the "central" cylindrical accumulator, right?
That one is a bit tricky, as the pressure is normally very high in any position. Although I do remember when I was tinkering on the ahc a bit more than these days, that sometimes I got nothing at that bleeder when cranking it open.
You might have to just protect yourself well and get it over with. The Ahc fluid is very bad for your skin if you don't wash it off right away, and use fully covering goggles. One good thing with a little squirt is that you don't risk getting any drill-dust into the accumulator as long as there is pressure pushing out.
 
I wouldn't attempt to do anything to the height accumulator while on the vehicle. Provided you can get all the connecting lines off it, I would bleed off the pressure in the system (from any of the lines or other bleeder screws) remove the accumulator and work on it from a bench.

Removing the broken bleeder screw will require some finesse and is not best done laying on your back with AHC fluid running down your arm.

You'll need to do a 'one can' flush once reinstalled. If it were me....while I had the system down...I'd replace ALL of the bleeder screws and the rubber protectors. Then you are good to go.
 
flintknapper said:
I wouldn't attempt to do anything to the height accumulator while on the vehicle. Provided you can get all the connecting lines off it, I would bleed off the pressure in the system (from any of the lines or other bleeder screws) remove the accumulator and work on it from a bench.

Removing the broken bleeder screw will require some finesse and is not best done laying on your back with AHC fluid running down your arm.

You'll need to do a 'one can' flush once reinstalled. If it were me....while I had the system down...I'd replace ALL of the bleeder screws and the rubber protectors. Then you are good to go.
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Perfect, now we're getting somewhere. So, if I can drain from the 4 other actuators at each wheel, then I can relieve some pressure when its time to drain from the Actuator. I wasn't sure if there was a lot of pressure "contained" in some isolated circuit specific to the accumulator. (obviously I know very little about the system.)

I just don't want to introduce air into the system and have computer issues later. I'll make sure to post up when I give this a go shortly! Thanks
 
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The pressure in the charged height accumulator will be about 10.5MPa and it is independent to the pressures in the front and rear hydraulic circuits - just cracking the four other bleed points will not relieve the stored pressure in the height accumulator unless the solenoids are augmented for a lift cycle. Try an easi out. There's a way to trick the system (and dump stored pressure) and raise from L to N without the pump running to recharge the height accumulator. I've done it before and surprised myself but in hindsight all it proved was that the system will return to N using stored pressure from the height accumulator if it can, as designed. In a previous life I worked on 3000-5000 psi systems and you learn very quickly not to underestimate the damage stored pressures, and bad info, can do.
 
mkivtdi said:
Perfect, now we're getting somewhere. So, if I can drain from the 4 other actuators at each wheel, then I can relieve some pressure when its time to drain from the Actuator. I wasn't sure if there was a lot of pressure "contained" in some isolated circuit specific to the AHC. (obviously I know very little about the system.)

I just don't want to introduce air into the system and have computer issues later. I'll make sure to post up when I give this a go shortly! Thanks
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Well....before you get started...understand that there IS pressure in the Height Accumulator (if working properly) and that it can be significant in some circumstances. When I bled mine...it was not an issue.

I will defer to PADDO's expertise here, but there is a way to relieve the pressure. IF you choose to just go at it with an EZ out, consider what you are dealing with. In order to use the EZ out you will need to drill a hole down the center of the bleeder screw which will significantly weaken it.
It won't allow fluid to escape until you either back the screw out a bit or it fails. But the idea of working on it with any appreciable amount of stored pressure and a compromised bleeder screw seems unwise IMO.

You must be able to 'control' the flow of pressurized fluid (if significant pressure is present). High pressure fluid escaping from a small orifice is capable of taking part of your finger off, or injecting fluid under the skin (not a good thing).

So just be careful.
 
Well, in a perfect world, I'd be able to pull this off the car and work on it on the bench in a more controlled environment.

But since we don't live in a perfect world, that why I needed to consider that plug suddeny failing and relieving the pressure behind it very quickly.

Would I have better luck trying to open up the hard line on the back of the accumulator very slowly, and reliving pressure that way, and then pull the unit off the car?

i just don't want to make a difficult situation worse. Literally one of the last things I need to address on the car
 
mkivtdi said:
I decided to start with the accumulator (driver's side between front and rear actuators) and, long story short, the nut was so rusted and seized on that the whole 'nipple' ripped off.
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I do not want to open a new topic and so hopefully I got help here :-) I have not ripped of the nut BUT it's rusted and wont move a bit. Already sprayed WD40 many times but it is not helping... Can I apply a bit of heat to the nut like you can do with rusted break line connections? Or is that not a good idea because of the AHC fluid?
 
The same thing happened to me about 3 weeks ago. Bleeder valve broke off on the accumulator. PB Blasted at each wheel to prevent same thing. I started on driver's side front first, and I think most of what was in the accumulator came out during that bleed. Then the rest of the wheels didn't take much to start seeing pink. There's no way I'm going to open that can of worms worrying about getting a new valve put in on the accumulator.
 
mstakacs said:
The same thing happened to me about 3 weeks ago. Bleeder valve broke off on the accumulator. PB Blasted at each wheel to prevent same thing. I started on driver's side front first, and I think most of what was in the accumulator came out during that bleed. Then the rest of the wheels didn't take much to start seeing pink. There's no way I'm going to open that can of worms worrying about getting a new valve put in on the accumulator.
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I have an accumulator chilling in the garage if you want an easy fix. PM me if interested. I'm around the Cincinnati area so Local pickup is a possibility....
 
Just a quick note regarding the amount of pressure in the AHC system. I recently changed out all four globes on my LC. I failed to adequately bleed off the pressure on the RR globe before unscrewing it. ( I bled through the bleed nipple prior to unscrewing the globe and thought I was good).

When I was down to just a couple threads left on the globe, it shot loose with a bang and sprayed fluid 20 feet across the garage, ripping the globe from my grasp in the process - good thing my hand was on the side of the globe, as it would have easily broken / crushed my hand when it popped off.
 
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