AHC system fluid leak... (4 Viewers)

[highalpinecruiser]

2006 LX470... After finding my front suspension practically as low as it could get, the AHC system on the dash was flashing OFF. I looked below to find what looked/smelled like suspension fluid... slow drips from somewhere in the wheel well. Can't pinpoint the leak as the top of tire is 1" from the wheel well ceiling.

Checked the fluid reservoir under the hood, completely dry. I got a 2.5L can of suspension fluid but am hesitant to fill as it would just leak right out.

Does anyone know the best way to track down the leak? Or at least what I should check first?

 

[OEMGUY0720]

Clean that area of front suspension area to dry, a regular household degreaser will do and put in about 1/4 quart of AHC fluid and observe, that’s the best I can recommend for you to do to pinpoint the leak.

 

[modus]

Following

 

[highalpinecruiser]

Front left vs. front right top of shock where the AHC connection hose connects... Looks like the O-ring got crushed.... right?

I began looking for parts and found just an O-ring for the AHC system, but not sure its purpose is what I am intending to use it for. Any clue if this is the correct O-ring and if replacing it would be feasible?

 

[OEMGUY0720]

That’s a actually a good sign the shock body is dry and leak appears to in the hydraulic fitting area on top. Could be a simple case of a loose fitting that you may just need to retighten. Go ahead clean that area with degreaser and water, allow it to dry and make sure to remove dirt using a brush to reduce risk or scoring the mating surface of the fitting before retightening it.

 

[highalpinecruiser]

When you mean tighten, are you referrring to the two bolts on top of of the shock where the pressure hose attachs?

There were some small fragments of the "cushion" that appeared to chip off. So I guess i need to just monitor the leak after tightening to see.

Some super helpful threads by said that replacement is not necessary unless the leaking is really bad. I am going to see how my globes are doing by observing the graduations in the reservoir.

Those threads also mentioned that adjusting the pressure with Techstream can slow/stop the leak... I think before i strip, bleed, and replace the current AHC shock absorber, I will attempt to slow the leak.


I am pretty novice in this department (if you can't tell), but think I am following the right procedure as of now?

 

[OEMGUY0720]

Yes that’s correct those two top fastening bolts securing the hydraulic line to the shock:

I would also recommend to inspect those bolts by removing them one at a time to see if it’s somehow stretched (maybe over-torqued) or stripped; hopefully not a case of any of the two. And yes it is just practical to replace the O-ring and Back Up Ring with a new one since the hydraulic line is dry and it’s already leaking as it sits so at some point that needs to be serviced to reduce the risk of the AHC system running dry. Good luck and keep us posted.

 

[2001LC]

There is a hard split ring (back-up ring) in with O-ring. Make sure you see it and place O-ring top. Lube o-ring, with AHC fluid, before install.

It is unusual for this O-ring to fail. Unless shock was replaced, and old o-ring reused. Nasty old fluid in system, for to long or pressure way to high.

 

[Zuberg]

Hopefully it's just the o-ring but there have been a few folks where it rusted through the top of the shock inside of the bushings.

Front AHC Shock Leak

Unfortunately it wasn’t apparent where the leak was coming from. I am confident the shock mount horn was dry above (should have ruled out the o-ring), and the leak/wet was originating at the top of the shock body between the shock and the frame, while installed. The old o-ring was in great...

forum.ih8mud.com

 

[kevgentile]

Hopefully it's just the o-ring but there have been a few folks where it rusted through the top of the shock inside of the bushings.

Front AHC Shock Leak

Unfortunately it wasn’t apparent where the leak was coming from. I am confident the shock mount horn was dry above (should have ruled out the o-ring), and the leak/wet was originating at the top of the shock body between the shock and the frame, while installed. The old o-ring was in great...

forum.ih8mud.com

My front are starting to look like the ones from that post. Fortunately, no leaks yet.
Odd since it's a rust free chassis. I have new rams sitting in my tool box with new seals too.

 

[IndroCruise]

2006 LX470... After finding my front suspension practically as low as it could get, the AHC system on the dash was flashing OFF. I looked below to find what looked/smelled like suspension fluid... slow drips from somewhere in the wheel well. Can't pinpoint the leak as the top of tire is 1" from the wheel well ceiling.

Checked the fluid reservoir under the hood, completely dry. I got a 2.5L can of suspension fluid but am hesitant to fill as it would just leak right out.

Does anyone know the best way to track down the leak? Or at least what I should check first?

As shown in your picture at Post #6 taken from the FSM, there are several different parts including retainers and cushions at the top of the ‘shock absorber’ -- which is just a hydraulic strut on AHC-equipped vehicles – it is not a damper in the manner of conventional suspensions. Damping takes place at the Damping Force Control Actuators to which the ‘globes’ are attached.

Suggest input your VIN at https://partsouq.com/ and explore towards the end of the “Power Train/Chassis” section looking for the AHC suspension information -- this provides a way of identifying the relevant Part Numbers. This was the source of the first two pictures below.

Your picture at Post #4 points at the top cushion. This is not an O-ring -- the relevant O-ring is not visible because it is inside the hydraulic connection – as depicted in this link:

Info on/experience with replacing O-Rings and Back Up Rings for AHC shocks (and globes)?

I'm replacing my front and rear AHC shocks with new ones and I note that the FSM advises replacing the O-rings and back up rings when doing so: If a description of how to do this exists on the forum (or elsewhere) I haven't been able to find it. Does anyone have instructions and/or...

forum.ih8mud.com

The cap bolts must be removed as depicted by @OEMGUY0720 in Post #7 to get to the internal O-ring 90301-11022 AND the back-up ring 90562-12003 as noted by @2001LC. These two rings are both vitally important, must be in the correct postion and are responsible for the pressure seals at this connection, not the cushion visible from the outside.

If taking on this job of dealing with the O-rings and back-up rings, it would worthwhile also to consider removing the each Front wheel to enable removal of both Front ‘shock absorbers’ and then replacing the top cushion and the bottom bush in each case. Unless the ‘shock absorber’ itself is rusted out or wildly leaking, replacement of the actual 'shock absorber' should not be necessary.

Your mention of “… threads also mentioned that adjusting the pressure with Techstream can slow/stop the leak”. This may not correct the leak discussed in this thread because it usually relates to leaks at the seals inside the actual ‘shock absorber’ caused by excessive AHC pressures. Often this latter kind of leak can be fixed by correcting AHC pressures.

Just to be clear, AHC pressure correction requires shifting more load onto the Front torsion bars and Rear coil springs and less load on the AHC system. Getting AHC pressures right has nothing to do with the condition of the ‘globes’. However, good ‘globes’ ARE one of the essential requirements for good ride comfort, so testing for good ‘globe’ condition is a good idea for that purpose.

The following link has some good pictures and a descriptive video which may help:

Front AHC shock bushing and cushion replacement - https://forum.ih8mud.com/threads/front-ahc-shock-bushing-and-cushion-replacement.1221355/

…. and some more detail at:

Successful AHC refresh - my experience and quick writeup - https://forum.ih8mud.com/threads/successful-ahc-refresh-my-experience-and-quick-writeup.1279980/

Hang in there! The AHC/TEMS systems are best “learned by working on them” – and they are among the simplest systems on LC100/LX470 vehicles -- way less complicated than brakes, steering, transmission, drivelines and axles, engine control, etc, etc, etc.

O-ring:

Back-up Ring: