KDSS Question (3 Viewers)

[bruisecruise]

I've seen videos where the KDSS lean is corrected by opening the KDSS shutter valves, compressing the KDSS pistons (located on the LH side) by rolling the LH wheels over a block of wood or by lifting the RH side to compress the left, and then closing the shutter valves. This seems to help 'balance' or correct for a bias in the system.

Does this mean if you disconnected the stabilizer bars entirely, opened the valves, pushed the KDSS pistons themselves all the way up (with floor jacks for example), and closed the valves that the pistons would stay compressed?

Two examples:

 

[bloc]

Does this mean if you disconnected the stabilizer bars entirely, opened the valves, pushed the KDSS pistons themselves all the way up (with floor jacks for example), and closed the valves that the pistons would stay compressed?

I’m not sure. Under normal circumstances there is a system to let fluid from the accumulators into the rams to slowly balance out things like parking on uneven surfaces, but forcing the rams up wouldn’t be normal circumstances. I don’t even know whether there is enough gas volume in the accumulators to allow both rams to be compressed in the first place. I can say you’ll see system pressures rise well above what is specified in the FSM for normal use.

What you are seeing in the videos is frankly an abuse of the system. They are overriding a safety mechanism built into the valve in an effort to force the sway bars into fighting a lean caused by something else.

Much more info about how the KDSS valve works here:

Anatomy of a KDSS valve

I think you guys and gals are gonna like this.. HUGE thanks to @jimoldguy who shipped me his rust-damaged KDSS valve after it was replaced for him with a new one. That can't have been cheap. Fortunately for me he kept the old one, and when I PM'd asking if he'd send it for a project I'm working...

forum.ih8mud.com

 

[bruisecruise]

I’m not sure. Under normal circumstances there is a system to let fluid from the accumulators into the rams to slowly balance out things like parking on uneven surfaces, but forcing the rams up wouldn’t be normal circumstances. I don’t even know whether there is enough gas volume in the accumulators to allow both rams to be compressed in the first place. I can say you’ll see system pressures rise well above what is specified in the FSM for normal use.

What you are seeing in the videos is frankly an abuse of the system. They are overriding a safety mechanism built into the valve in an effort to force the sway bars into fighting a lean caused by something else.

Much more info about how the KDSS valve works here:

Anatomy of a KDSS valve

I think you guys and gals are gonna like this.. HUGE thanks to @jimoldguy who shipped me his rust-damaged KDSS valve after it was replaced for him with a new one. That can't have been cheap. Fortunately for me he kept the old one, and when I PM'd asking if he'd send it for a project I'm working...

forum.ih8mud.com

If I'm understanding the KDSS diagram I normally see, only one accumulator will be compressed and the other will be uncompressed, not both.

Full disclosure I have a 4runner but I feel like the LC community might be more technical. Is there any functional differences with the LC KDSS versus the 4Runner?

I feel pretty confident that the system will allow the pistons to fully compress at maximum articulation, also I was doing this with the shutter valves open so the pressure should be equalized between the high and low sides. In the testing I've done though, the pistons always return to their full length, regardless of the amount of fluid I move from the high to low side (or vice versa) across the shutter valves. I'm guessing the intrinsic force of the piston pushing down is enough to overcome the pressure of the accumulators.

I'm trying to figure out how all the discussion about 'calibrating' the KDSS piston position works, from what I've experienced it really shouldn't be possible because the pistons always extend. There's no way to keep a piston in a 'neutral' position with the fixed stabilizer bar link.

 

[2021 LC200]

On a 200 series I do not think lean can be corrected by KDSS in the long term (I actually assume on the 4 Runner and GX as well, however never looked at that setup in detail). You can maybe temporary force the lean to be cancelled, but within days it will be back to the position the springs and weight distribution of the vehicle is pushing it towards, as the system is not perfectly sealed between yellow and green sides.

Now it is possible when you work on a vehicle (e.g. I experienced this during a tire rotation at home and having lunch in between) that you create a lean which is temporarily forced by KDSS. The way to resolve is a two turns on the hex (like on my 2021) or allen (older 200) bolts and let the vehicle settle (either parked and rocking it some like i did, standing on the running boards and using the roofrack or by driving around) and close it up again.

I have expanded on how KDSS works in another thread. The 200 series has no electronics like the GX and the 4 Runner. Nice and simple.

KDSS Stupid

Yes I’m going to do it myself. Replaced KDSS unit because of rusted hex bolts. Called 6 dealers around my area and all 6 don’t know what KDSS do. Do you also know the SST tool part number for LC200? I don’t, but it has been covered online elsewhere. Not too difficult to find. Same as on 4runners.

forum.ih8mud.com

Copying the simplified diagram below, including the blue representing the hex/allen bolts allowing equalization (2 turns open) or isolation (normal closed position) between the yellow and green parts of the system.

 

[bruisecruise]

I do not think lean can be corrected by KDSS in the long term on a 200 series. You can maybe temporary force the lean to be cancelled, but within days it will be back to the position the springs and weight distribution of the vehicle is pushing it as the system is not perfectly sealed between yellow and green sides.

Now it is possible when you work on a vehicle (e.g. I experienced this during a tire rotation at home and having lunch in between) that you create a lean which is temporarily forced by KDSS. The way to resolve is a two turns on the hex (like on my 2021) or allen (older 200) bolts and let the vehicle settle (either parked and rocking it some like i did, standing on the running boards and using the roofrack or by driving around) and close it up again.

I have expanded on how KDSS works in another thread. The 200 series has no electronics like the GX and the 4 Runner. Nice and simple.

KDSS Stupid

Yes I’m going to do it myself. Replaced KDSS unit because of rusted hex bolts. Called 6 dealers around my area and all 6 don’t know what KDSS do. Do you also know the SST tool part number for LC200? I don’t, but it has been covered online elsewhere. Not too difficult to find. Same as on 4runners.

forum.ih8mud.com

Copying the simplified diagram below, including the blue representing the hex/allen bolts allowing equalization (2 turns open) or isolation (normal closed position) between the yellow and green parts of the system.
View attachment 3825535

Perfect this is similar to the diagram I posted. So, theoretically, if you open the valves marked by blue (the hex bolts, called the ‘shutter valves’ by FSM), move the pistons up such that most of the fluid moves from the high (yellow) side to the low (green) side, then close the valves, would the pistons stay up (suspended by pressure below) or still come down?

Your simplified diagram doesn’t have the accumulators which may make answering more complicated. From my practical experience though, doing exactly what I described above, the pistons still come back down to full extension. Now I just want to know why!

 

[bloc]

If I'm understanding the KDSS diagram I normally see, only one accumulator will be compressed and the other will be uncompressed, not both.

View attachment 3825441

Full disclosure I have a 4runner but I feel like the LC community might be more technical. Is there any functional differences with the LC KDSS versus the 4Runner?

I can't speak to the 4runner arrangement other than I know it's different due to yours having an electrical harness and ours not.

I also do know that both accumulators on a LC are plumbed to the same channel, as trying to understand that bit of the plumbing is what prompted me to cut the valve up in the first place.

 

[bloc]

From my practical experience though, doing exactly what I described above, the pistons still come back down to full extension. Now I just want to know why!

Not to continually reference my own stuff but it's probably the part in this post:

Anatomy of a KDSS valve

I think you guys and gals are gonna like this.. HUGE thanks to @jimoldguy who shipped me his rust-damaged KDSS valve after it was replaced for him with a new one. That can't have been cheap. Fortunately for me he kept the old one, and when I PM'd asking if he'd send it for a project I'm working...

forum.ih8mud.com

 

[2021 LC200]

Your simplified diagram doesn’t have the accumulators which may make answering more complicated. From my practical experience though, doing exactly what I described above, the pistons still come back down to full extension. Now I just want to know why!

This is when you have the vehicle in the air and are working on the suspension? Your question is whether you can or cannot have more yellow or green fluid by changing the suspension height? I would think so.

I only recall installing the airbagman airbags on the rear axle and disconnecting the KDSS on the driver side rear made the actuator fully extend. Had to use a jack to push it back and reconnect the stabilizer bar. Did have the shutter valves 2 turns open. I have not reasoned through whether that makes sense based on the simplified hydraulic diagram and position of the shutter valves. I think it is like dropping one wheel on one side and the KDSS goes to full articulation.