KDSS gurus, I believe I'm a rare failure case

linuxgod

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What's interesting is that this isn't any sort of expected failure mode for KDSS. Everything in that case points to too much body roll if there's air in the system, not an overly firm system.

It's certainly possible this is a KDSS failure of course, especially since you get a bit of fluid weeping by when you start to open the valves. Maybe the accumulator is frozen? They are supposed to have a gas inside which will allow for fluid to expand into it, but if it's stuck, or if the air somehow migrated out and so the accumulators are filled only with oil, perhaps that's why it gets stiff?

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linuxgod

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Badly worded on my part.

What I'm trying to wrap my mind around is that the common failure modes of the system is a reduction in roll stiffness. Which is what would be expected in a pressurized and hydraulically interconnected system. What I was trying to say is that the softness he's experiencing as normal could be the KDSS operating in compromised fashion due to loss of pressure. And with heat and use, the system comes up to sufficient pressure to engage the pop-valves and accumulators sufficiently where it then operates more normally, but is perceived as harsh? I'm not really keen on that theory, but threw it out there. There's definitely been comments from other platforms with the newer KDSS where it's possible to electronically disengage KDSS at speed, to compare back-to-back, where they start noting some constraints of the KDSS for small bump compliance.

I'm still thinking an accumulator issue. If not a failure, could be overfill. The steps to bleed and charge the system has a tech pressurizing the system to over 1k PSI, bleed at 725psi, and settle at 435 psi. If the system pressure is too high, wouldn't allow the accumulators sufficient reserve volume and possible bottoming out.



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hah, you beat me to the same comment by 3 minutes...
 

bloc

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Thing is even if the accumulators did develop a nitrogen leak past the bellows that nitrogen would just be in the larger system now, most likely finding high points, until the system gets moving then maybe it would be dispersed. Either way it’s still there as long as the system has pressure, which means there is compressible volume in the system to deal with temp or displaced volume changes.

Though, if the nitrogen is no longer in the accumulators, over pressure in the top or bottom circuit would get bled to the central circuit possibly with no nitrogen (aka room to receive the fluid).

@montegofd3s you mention a new lean.. is this persisting? Does having the screws open alleviate?

I’m reminded of two reports of failed KDSS systems that both developed significant leans. I still don’t understand exactly how/why this happens, but they can’t just be coincidence.
 
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Op mentioned having BP51s, is the harsh ride related to any system failure with that element of the suspension setup?
That’s my thought. None of what he described is symptomatic of KDSS failure, which i can count on one hand minus a few fingers. We’re not talking about AHC here. I would point my finger at BP51s.
 

bloc

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Even suspension would seem odd to start acting up at 4hrs of driving..

Either way I’m glued to this thread. And I’ve already discussed with OP if it does turn out to be KDSS I’ll try to postmortem that valve too. Though I’m genuinely hoping it’s something much cheaper & more simple.
 

empty80

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👀

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Edit: Also require ARB Part # VM80010004 with BP-51s.
 
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empty80

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Even suspension would seem odd to start acting up at 4hrs of driving..
It would seem odd unless the reservoirs lost the nitrogen pressure. The purpose of the nitrogen gas in the reservoir is to help keep the oil in its original form. If that pressure is gone, there is nothing to stop the remaining gas in the reservoir from mixing with the oil. That mixture could prevent the anticipated flow through the pistons creating harshness and immobility.

Think about filling a sealed container 3/4 full of milk and shaking. Eventually, the mixture doesn't move as freely.

It doesn't explain the KDSS anomalies, but I would certainly verify reservoir nitrogen pressures before getting any more handsy with the KDSS system.
 
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Update, had time to get under the truck today. I went to bleed the pressure from the bleeder screw on the KDSS body and not a drop of fluid came out. I then pulled the balance screw I knew was leaking and as suspected I found the o-ring broken. Also, no fluid flowed out. This leads me to suspect I've been slowly leaking down over time. I'm not sure where the fluid leaked from (maybe under a ram boot is my guess), but I am going to replace this ring and try to find a dealer to bleed the system. I haven't had any luck finding one in the area yet. I contacted my buddy who works at the local dealer and he said they never had the tool. Go figure.

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bloc

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Update, had time to get under the truck today. I went to bleed the pressure from the bleeder screw on the KDSS body and not a drop of fluid came out. I then pulled the balance screw I knew was leaking and as suspected I found the o-ring broken. Also, no fluid flowed out. This leads me to suspect I've been slowly leaking down over time. I'm not sure where the fluid leaked from (maybe under a ram boot is my guess), but I am going to replace this ring and try to find a dealer to bleed the system. I haven't had any luck finding one in the area yet. I contacted my buddy who works at the local dealer and he said they never had the tool. Go figure.

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My understanding was most dealers loan the tool as part of a regional program.

On the o-ring, I wonder whether it was damaged previously from someone opening the screws too far then going “oh s***!” and running it back in.. if the bore looks good there is no reason it should have torn.

I’d bet it is a standard metric size, but your material choice and durometer could potentially be very important. Viton is often a great choice, but even that comes in different durometers.
 
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My understanding was most dealers loan the tool as part of a regional program.

On the o-ring, I wonder whether it was damaged previously from someone opening the screws too far then going “oh s***!” and running it back in.. if the bore looks good there is no reason it should have torn.

I’d bet it is a standard metric size, but your material choice and durometer could potentially be very important. Viton is often a great choice, but even that comes in different durometers.
I am wondering the same thing, and that is actually my bet. I'm going to try to find another o-ring, but I'm not even really sure where to start with that one 😂
 

bloc

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Durometer is effectively how hard an elastomer (rubber) is. Higher number makes it start to resemble plastic, lower and it is softer. RTV would be very low durometer. Something like a rubber thermostat gasket if you’ve ever messed with that would be medium. High durometer.. harder to find, but used in higher pressure applications or where we need to protect from mechanical damage.

I’d try to call some local places specializing in custom gaskets. This is a super tiny order for them, but they can put you in touch with someone that can size the oring and discuss materials.

For now you can start sizing things if you have a set of vernier calipers. Measure the OD of the narrow part of the screw where the oring fits. The bore is probably an even mm number.. if you have spare bolts lying around see if something slides in there with minimal play, being careful not to force things to cause damage. I tossed the remaining parts of my dissected valve or I’d get some measurements for you.

Then compare those numbers to a metric o-ring size chart. It’ll all be pretty standard.

The place helping size the oring may want an intact one.. you might need to try and pull the other screw. Since you are bleeding the system and I’m assuming there isn’t damage in that bore, this should be low-risk. Just lubricate them with KDSS fluid before reinstalling. I wouldn’t use grease because we don’t know if this can impact some function of the system once it is all bled and operational again.
 

empty80

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Update, had time to get under the truck today. I went to bleed the pressure from the bleeder screw on the KDSS body and not a drop of fluid came out. I then pulled the balance screw I knew was leaking and as suspected I found the o-ring broken. Also, no fluid flowed out. This leads me to suspect I've been slowly leaking down over time. I'm not sure where the fluid leaked from (maybe under a ram boot is my guess), but I am going to replace this ring and try to find a dealer to bleed the system. I haven't had any luck finding one in the area yet. I contacted my buddy who works at the local dealer and he said they never had the tool. Go figure.
Very unfortunate and also interesting that there's not evidence of a leak.

Maybe it would be worth having a look at this o-ring part number before guessing. Toyota system says it’s a cooling part, but it also features in the KDSS exploded diagrams. Shouldn’t be hard to get for a test fit since it is appears to be pretty ubiquitous in Toyotas.

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Very unfortunate and also interesting that there's not evidence of a leak.

Maybe it would be worth having a look at this o-ring part number before guessing. Toyota system says it’s a cooling part, but it also features in the KDSS exploded diagrams. Shouldn’t be hard to get for a test fit since it is appears to be pretty ubiquitous in Toyotas.

View attachment 3065327

Great call! I just ordered 2 so we shall see.

On another note, I may have a lead on a service pump, but am trying to find the full KDSS bleed procedure for the LC. I found it for the 4Runner, but I don't know if it is exactly the same. I had a link bookmarked, but that link is now broken. Does anyone have the procedure?
 

empty80

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Great call! I just ordered 2 so we shall see.

On another note, I may have a lead on a service pump, but am trying to find the full KDSS bleed procedure for the LC. I found it for the 4Runner, but I don't know if it is exactly the same. I had a link bookmarked, but that link is now broken. Does anyone have the procedure?
If you PM your email adress, I’ll send it to you.
 

bloc

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Those orings are cheap enough to try, but appear to be for the shuttle valves in the service adapters. I don't see a parts breakdown of the KDSS valve itself indicating they would work.

Still, since they are for use within the system they should be resistant to the oil and pressure levels we'll see.
 
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Small update, the o-rings are not the correct ones, but I have a few generic ones I am going to try and see if they will work.

On another note, I cannot find a dealer anywhere close that had the SST tool so I made one. Let's see what happens.
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empty80

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Small update, the o-rings are not the correct ones, but I have a few generic ones I am going to try and see if they will work.

Bummer! That’s a neat tool you’ve developed!
 
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Bummer! That’s a neat tool you’ve developed!
Yeah, but it was worth a shot and I'm sure I'll find a use next radiator flush or something.
 

bloc

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PLEASE break down how to build one if possible. Much of it is obvious but things like the type of quick disconnect fittings used would save others a ton of leg work.

As for the generic orings.. maybe not bad to try and find a size, but unless you are sure they are 65 duromerer or higher I’d be reluctant to use them long term. Some orings come in soft material and may not handle the pressure, especially as things heat up under the truck.

I guess the good thing is the bleeding pressure is higher than the operational pressure, so if you have an oring failure it is less likely to be out on the road somewhere.
 
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