Definitive list of AHC maintenance items (4 Viewers)
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Ok folks, I'm reviving this for a quick question, hopefully you gurus can help a guy out.
Long story short, I asked the local dealership to do an AHC drain/fill when they were doing my timing belt at 180k (they are familiar with LCs and have a good reputation). I picked it up yesterday, now the truck rides nicely but it's definitely a little stiffer. I break out the handy Techstream to find my neutral pressures have gone up since I last cranked the TBs in May of this year. I still get at least 7 gradations on the reservoir. No word on the color of the fluid that came out (tech is off until Monday), but I did a @PADDO flush myself maybe 30k miles ago(?). I'll report back when I get word from the tech on how the fluid looked. No other comments from the dealership other than the truck is in great shape underneath with no bad rust on accumulators/globes.
TL/DR: Truck rides stiffer after dealer performed AHC flush, neutral pressures have gone up, still get at least 7 gradations from LOW to HIGH
Here are the specs:
Before flush: Taken in May 2018, truck was riding "normal" and I had just done 3 cranks on the TBs.
After flush 11/17/18: truck riding a little stiffer but not uncomfortable:
What could they have possibly done that could cause that neutral pressures to jump? Do I need to have them take a second look to get those pressures down somehow? Are my springs in need of replacement? Any thoughts would be much appreciated as I have to bring it back anyway for the to re-align (steering wheel is slightly off center).
Thanks!
Long story short, I asked the local dealership to do an AHC drain/fill when they were doing my timing belt at 180k (they are familiar with LCs and have a good reputation). I picked it up yesterday, now the truck rides nicely but it's definitely a little stiffer. I break out the handy Techstream to find my neutral pressures have gone up since I last cranked the TBs in May of this year. I still get at least 7 gradations on the reservoir. No word on the color of the fluid that came out (tech is off until Monday), but I did a @PADDO flush myself maybe 30k miles ago(?). I'll report back when I get word from the tech on how the fluid looked. No other comments from the dealership other than the truck is in great shape underneath with no bad rust on accumulators/globes.
TL/DR: Truck rides stiffer after dealer performed AHC flush, neutral pressures have gone up, still get at least 7 gradations from LOW to HIGH
Here are the specs:
Before flush: Taken in May 2018, truck was riding "normal" and I had just done 3 cranks on the TBs.
After flush 11/17/18: truck riding a little stiffer but not uncomfortable:
What could they have possibly done that could cause that neutral pressures to jump? Do I need to have them take a second look to get those pressures down somehow? Are my springs in need of replacement? Any thoughts would be much appreciated as I have to bring it back anyway for the to re-align (steering wheel is slightly off center).
Thanks!
Addition: Found a huge new leak in the rear hatch after having asked the dealership to tighten the hinge bolts on one of the third row windows, that'll definitely be coming up when I head back in tomorrow, tech probably missed putting a gasket back together or similar.
Any help with AHC issue above is appreciated, I'm thinking I'll ask them to crank the TBs to get the fronts back to spec and then discuss the need to replace the rear springs in the future (note, don't do much towing or heavy lifting with this truck aside from loading it up with friends and ski gear). I just found it odd that the front jumped so much and the ride is noticeably stiffer (maybe my perspective is off and it was actually too soft from the beginning).
Any help with AHC issue above is appreciated, I'm thinking I'll ask them to crank the TBs to get the fronts back to spec and then discuss the need to replace the rear springs in the future (note, don't do much towing or heavy lifting with this truck aside from loading it up with friends and ski gear). I just found it odd that the front jumped so much and the ride is noticeably stiffer (maybe my perspective is off and it was actually too soft from the beginning).
uHu
Bridgeburner
On the AHC, first check your heights. The numbers in TechStream mean nothing if you haven't checked the physical height of each end.
If your heights are right, you do need to change the coils. For the front, it's like always - adjust TBs until press is OK, while observing L/R lean.
If your heights are right, you do need to change the coils. For the front, it's like always - adjust TBs until press is OK, while observing L/R lean.
Great point on checking the height first. What is that FR/R height supposed to be, and assume it’s measured from center of wheel?
The front pressure changes ~2.2MPa per inch (stock weight front end) so it doesn’t take very much of a height variation, parking on a slope or whatever to see a small difference in pressure readings compared to readings you took months earlier. Don’t forget the moment you change height or weight or both you affect pressure and one off pressure readings don’t mean much at all in the absence of their height/weight context. Also I’ve seen enough variations, both slight and gross, in Techstream pressure readings to not be 100% confident the pressure you’re picking off the pump output during the solenoid switching cycle accurately represents actual pressure at the damper assemblies. At a minimum do three L to N lifts and take the median pressure, or use a gauge.
I ended up doing 3 turns on the TBs on both sides and got front pressure down to 6.8 (from 7.5) and the rear to 7.3 (also from 7.5). It's a little odd that the rear actually went down rather than up but I'll take it. All readings were done with just me in the car with nothing/nobody else on the same slope etc. in an attempt to be as consistent as possible.
The encouraging things is that the dealership said the old fluid was in pretty good shape. My service history shows new globes all around at 99k miles (previous owner) so I would hope they've still got plenty of life left in them.
I still have to drive it a bit to see if things have "softened" up at all but I'm happy with how close to within spec the rear is now. At 180k miles, I suppose that there's a possibility I'll be needing new rear springs sometime soon to bring those rear pressures down further.
The encouraging things is that the dealership said the old fluid was in pretty good shape. My service history shows new globes all around at 99k miles (previous owner) so I would hope they've still got plenty of life left in them.
I still have to drive it a bit to see if things have "softened" up at all but I'm happy with how close to within spec the rear is now. At 180k miles, I suppose that there's a possibility I'll be needing new rear springs sometime soon to bring those rear pressures down further.
Guys having trouble turning the torsion bars tryed WD 40 etc won't move with a ring spanner .What's the best option ?.
James Bentley
SILVER Star
I got my Techstream working and found Front at 8.2 and Rear at 7.0 Accumulator at 10.6
PO had the dealer replace all 4 AHC shocks (weeping/leaking)
9 graduations from L to H
kind of cool today at 57 and AHC temp sensor NOT unplugged for test
Got my fluid ready for the AHC flush as per @PADDO and will run a retest of pressures prior to checking/setting heights and then turn the TB's to get the front pressure down.
PO had the dealer replace all 4 AHC shocks (weeping/leaking)
9 graduations from L to H
kind of cool today at 57 and AHC temp sensor NOT unplugged for test
Got my fluid ready for the AHC flush as per @PADDO and will run a retest of pressures prior to checking/setting heights and then turn the TB's to get the front pressure down.
04 lx470 after putting some bigger tires on I've noticed it's been riding a bit rougher. I checked measurements and was 21.5" on the front wheels to the fenders. So I cranked the TB's ccw about 10 times, measured and it was still a bit too high. Hit it again a few more times until I got both to 19.5".
While checking number of marks of change between L and H, I can't get it outta L now. Prior to cranking the TB's, I was able to move from L to H and back about 5 times. Tried using techstream to see if something was wrong, no dtcs. Went through a few of the tests within techstream via the signal check which moves the ahc to off mode. Turn the key off, restart and turn ahc back on and still can't get outta L.
Both the 50a and 15a fuses are good.
Should I try to Tc and E1 reset now?
I'm puzzled what happened at this point. I think I've got it in some weird state. Perhaps a failing sensor?
Edit, I've also once gotten it into Normal, but it will not move to High. Same condition where the HI flashes, but the vehicle never moves up. I'm sure I can get it to LO, but it will be stuck in Low until I get it back to N.
Thoughts??
While checking number of marks of change between L and H, I can't get it outta L now. Prior to cranking the TB's, I was able to move from L to H and back about 5 times. Tried using techstream to see if something was wrong, no dtcs. Went through a few of the tests within techstream via the signal check which moves the ahc to off mode. Turn the key off, restart and turn ahc back on and still can't get outta L.
Both the 50a and 15a fuses are good.
Should I try to Tc and E1 reset now?
I'm puzzled what happened at this point. I think I've got it in some weird state. Perhaps a failing sensor?
Edit, I've also once gotten it into Normal, but it will not move to High. Same condition where the HI flashes, but the vehicle never moves up. I'm sure I can get it to LO, but it will be stuck in Low until I get it back to N.
Thoughts??
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James Bentley
SILVER Star
What happens if you go back 10 turns CW (undo what you did with the TB's)?
I tried 5 turns and then 10. Same thing, light just flashes in N when stuck in LO. Currently I'm in N, but can't get to HI now, and I'm sure it will go to LO, but then I won't be able to get back to N.
Suspect pulling the fuses is what got me back into N for now. Measurements from center of wheel to fender seem to indicate I'm around N again after I've cranked the TBs.
Just want to make sure it moves between HI and LO as designed.
Suspect pulling the fuses is what got me back into N for now. Measurements from center of wheel to fender seem to indicate I'm around N again after I've cranked the TBs.
Just want to make sure it moves between HI and LO as designed.
You turned the TBs ccw to lower the front end height? You don’t do that for AHC vehicles: you adjust the height sensors then tweak pressures if necessary to suit the new height. 10 ccw turns will increase front pressure about 2MPa and that’s not good at all. Undo what you did and clear any DTCs.
Yes, the pressure readings were 9.1 on the front before I turned the TBs.
Ok, guess I need to read a bit more on this.
Does a lower (but acceptable) number of graduations indicate a shorter expected remaining life for the AHC, or is this something that varies from vehicle to vehicle, and any number of graduations above 6 is all that matters?
In other words, does 7 ticks mean "on the decline and close to inevitable failure"?
uHu
Bridgeburner
If pressure and heights are within specs, the 7 ticks means time to change globes.
Without checking heights and pressures, the tickmarks mean next to nothing.
Without checking heights and pressures, the tickmarks mean next to nothing.
Ah, was going to ask the proper method for changing height. Was making the assumption it was going to be in the sensor arms but you answered that. I didn't disconnect the temp sensor or check my heights but I did find I had 8-9 graduations from low to high and landed at 7.8 front 6.9 rear (2006 w/ ~170k miles). What's the impact of the temp sensor?
Planning this weekend to make some adjustments and grease my drive shafts.
