Today I finally fixed very annoying play in steering. But NOT 100% fixed. I replaced bushings. There is 4 needed. But in reality, only 2 needed to be replaced, shown in circles. Picture shows bad one. It fixed all left-to-right play. However, I still have little up-down play (much less than it was) but I think now I need to replace that plastic bush/nut circled with X it looks damaged and I think it's adding to the issue. Overall almost fixed.
Also replaced clock spring. Made unpleasant noises, hopefully going to be fixed as well.
With AHC, if anyone knows - please comment. I did bleed per FSM twice. From what I can tell - front ones - fluid comes out steady and clear. Rears - steady but foamy. I did it twice.
Another thing - torsion bars. Left side is sagging. I understand AHC has nothing to do with it, right? Or not? Sensors just get averaged out, but pressure is equally distributed, correct? Currently I didn't look at computer, sensors set in a middle position, I am just trying to get height correct.
Anyways. According to adjusters they are both out of spec now, right side is over-loose and left side is over-tight. And yet I still have left side sitting 1 inch lower at N (more at H)
So.. Should I reindex or I should be fine with using adjusters as long as they don't bottom out (or start coming out of nut)?
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katit:
“I did bleed per FSM twice. From what I can tell - front ones - fluid comes out steady and clear. Rears - steady but foamy. I did it twice”:
IndroCruise: Froth and bubbles mean gas.
Either it is nitrogen from a ruptured membrane – possibly this should be suspected if ‘globes’ are old and in doubtful condition. It is less likely when ‘globes’ are known to be in good condition.
More likely, air is trapped somewhere in the system, particularly in the following circumstances:
- air is trapped in the extremities such as in the ‘shock absorbers’. Even when the vehicle is resting on the bump stops the ‘shock absorbers’ still contain a volume of fluid – if air is in this fluid, it can take multiple raise/lower/bleed cycles to get this air to move. Note that in these cycles, fluid is being pushed into the ‘shock absorbers’ by the AHC Pump, then pushed back out again when the vehicle drops BUT not all of the fluid is moved – it is never a clean flush because of the remnant fluid left behind and which may contain air. Multiple cycles aim to dilute and eventual replace the air-infected fluid.
OR
- air is trapped somewhere in the long lengths of pipes from the AHC Pump through the Control Valve Assembly and onwards to the bleeders. Imagine a ‘plug’ of air somewhere along the line. This must be pushed all the way through the system and out through the bleeders. The reason for multiple cycles is because the early cycles may only (in part) be compressing the air, and not fully displacing fluid.
OR
- air is trapped in the Height Control Accumulator (HCA), meaning the long cylinder mid-way along the LHS chassis rail. The HCA is a special case. It is controlled by the solenoid valve at the front end. This solenoid valve is ‘normally closed’. There are only two points in the cycle when this valve opens: (i) when the AHC Pump is filling the HCA after completion of a raise, and, (ii) when the HCA is initiating a raise L >> N or N >> L when it is releasing fluid under pressure into the system, eventually to the ‘shock absorbers which causes the vehicle to raise. This is why the raise/lower cycles are important when bleeding. The only way to cause fluid in the HCA to move out through the bleeder is to open the bleeder after being quite sure that there has been enough time at the end of a previous raise to fill the HCA. Theoretically this might be about 15 seconds after the raise has stopped and indicator light has settled at “N” or “H” BUT allow say 60 seconds just to be sure, especially if there is air suspected in the system or pressures which are too high or suspicions about partial blockages, either of which may cause slow or incomplete filling operation by the AHC Pump. Obviously it is pointless to bleed the HCA unless sure that it has been filled.
OR
OR
- Bleeding is undertaken from only one side of the vehicle. This is fine in theory because when the vehicle is stationary, the Front Gate Valve (in the Control Valve Assembly) is open and AHC Front Left is connected hydraulically to AHC Front Right. Pressures are equalised and fluid can flow between them. Ditto Rear AHC. But note that Front AHC and Rear AHC are not hydraulically connected. However, in practice if there is an air problem, where is the air actually located?? This is unknown. If there are bleeding difficulties, then bleed ALL five bleeders over multiple cycles.
OR
- Air-infected fluid is re-used in the bleeding process, thereby re-introducing air and particulates into the system. Some folks are prepared to accept this risk. If certainty is required, use only fresh fluid.
Often AHC bleeding is a straightforward happy experience. Sometimes it takes multiple cycles (more than two cycles) and lots of patience and persistence!!
Hydraulic Circuit when vehicle is lowered - the difference from this diagram during bleeding is that the fluid exits at the bleeders, does not return to the AHC Tank:
katit: “Another thing - torsion bars. Left side is sagging. I understand AHC has nothing to do with it, right? Or not? Sensors just get averaged out, but pressure is equally distributed, correct? Currently I didn't look at computer, sensors set in a middle position, I am just trying to get height correct.
Anyways. According to adjusters they are both out of spec now, right side is over-loose and left side is over-tight. And yet I still have left side sitting 1 inch lower at N (more at H)
So.. Should I reindex or I should be fine with using adjusters as long as they don't bottom out (or start coming out of nut)?”
IndroCruise: Yes – exactly correct. ‘Cross-levelling’ is not done, cannot be done by the AHC system. The AHC system on LC100/LX470 is a two-channel system – Front and Rear. It is not a four-channel system. It cannot raise or lower or auto-adjust the heights of each of the four wheels independently of one another.
So after all other work is completed, setting up a vehicle with AHC always starts with ‘cross-levelling’ at the Front on level ground with no eccentric loads in or on the vehicle. This means using the Torsion Bar adjusters to equalise the hub-to-fender measurements at Front Right and Left Front with a tape-measure (FSM tolerance +/- 10 millimetres), nothing to do with Height Control Sensor adjusters. This
may involve re-indexing if available thread on the adjuster bolts are insufficient. Note: Some leeway -- available thread -- is needed on the adjuster bolts because these will be used later when it comes time to use the adjuster bolts to adjust torsion bar loads and achieve correct Front AHC pressures.
On an AHC vehicle, the Torsion Bar adjusters have nothing to do with setting the ‘ride height’ or ‘operating height’ of the vehicle.
The purpose of Front cross-levelling is to have the Right and Left torsion bars carrying equal shares of the vehicle weight so that the vehilce performs Right and Left turns similarly (assuming steering geometry already has been correctly adjusted), and, to correct side-to-side lean which otherwise will complicate the later adjustments of ‘ride height’ also called ‘operating height’.
‘Ride height’ or ‘operating height’ is done later by moving the Height Control Sensor adjusters until they are all as close as possible to zero on Techstream when the vehicle is at the desired Front and Rear heights for the “N” height setting at the AHC controls on the centre console.
Theoretically in a vehicle with perfect geometry, if the Front is ‘cross-levelled’ correctly then Rear also is ‘cross-levelled’ correctly. The Rear cannot be different unless there is some cause of tilt or twist. In practice, a 14 to 22 year old vehicle will not be perfect due to manufacturing tolerances, wear and tear, some minor chassis twist, etc, etc and there may be some difference across the Rear heights.
It is important to be quite sure that all three Height Control Sensors are in good electrical condition and working correctly. Otherwise, there will be conflicting signals (voltages) sent by the Sensors to the Electronic Control Unit (ECU). Huge frustration then is guaranteed when trying to set ‘ride heights’ a.k.a. ‘operating heights’. Poor Sensors mean erratic signals and erratic suspension behaviour. If the voltage signals from the three Sensors are widely different and the ECU cannot resolve the conflict, then the ECU is unable to determine the auto-adjustment position at “N” (or any other height selected by the driver). Then the ECU will choose the version of ‘fail safe’ mode associated with Sensor problems. This mode prevents proper AHC operation and prevents adaptive damping, meaning that ride quality will be poor. Depending on the actual signal from any Sensor, there may or may not be a DTC associated with this 'fail safe' mode. Absence of a DTC does not provide assurance that all is well with the Height Control Sensor(s).
forum.ih8mud.com
It seemed to me that I saw it in FSM, but I was wrong.
