Story Time:
2013 LX570 111,000mi - California truck with no rust.
I posted in the SQOD thread that on a flush from Normal height there was a suction on the reservoir and that breaking the suction kept things running well when repressurizing the system. The pump took a very long time to regain pressure and it took 3-4 times of breaking suction. If I didn't break the suction the pump started to sound louder and louder as if it were cavitating. In familiarizing myself with the vent on the cap it seems like it only allows air out to avoid positive pressure when lowering, but doesn't allow air in.
After the flush and the system came back up to pressure with the system at Normal height, I cycled through to High and then back to Normal and everything worked as intended. I put easy access back on as usual and cleaned up shop.
Fast forward to the drive home from the shop at my parent's place - start the LX up and the pump is making a high pitched whine and doesn't come out of Low. I drive home and let the truck sit for a few days. Today I take the truck back and go through the following steps thanks to a few posts
@TeCKis300 has made in various AHC threads.
- Added an extra .5 liter of fluid
- Bled 5th accumulator [not much pressure at all or fluid]
- Cracked Rear No 6 Height Control Tube
- Let fluid run out while truck was off to ensure prime
Started the truck back up and the same pump whine was persistent with .16mpa pressure showing from techstream. I noticed it was very slowly building pressure though, three cycles of clearing codes and it was up to 2.89mpa. I primed the pump once more by disconnecting the No 6 tube completely and running the pump, a good amount of fluid emptied into a catch can. Fired the truck up again and it wasn't getting above the 2.89mpa. So I did what
@llaga did and used a small hand pump to pressurize the reservoir while it was running and immediately the pump started to pressurize the system and work as it always had been.
Truck rose to Normal and the pump stopped. Pressure was reading ~8.75mpa and I tried to go to High mode. No bueno. Tried to lower to Low and it proceeds as it should. Restart the truck and try to bring it back up to Normal and no luck, even with applying a little positive pressure. I noticed the pump was making a ticking noise and was a bit unstable in it's rpm.
Here's a video [caution it might be loud]:
My next step is to drop the pump and inspect the reservoir. I feel like there might be something on the inlet side of the pump whether it's air or debris. At the same time I'm going to order another pump & res assembly, as it might be on it's way out after all this. The truck isn't on the bump stops, but should I try bleeding again?
--
Unfortunately I'm what, the 4th report in a month with similar issues? Is there something similar between all of us? I love the AHC system, have flushed it and replaced the front struts without any issues. Hope this help adds more data and maybe some of the knowledgeable AHC dudes can chime in if there is something I haven't tried yet.
//Root Cause
To update the thread, it seems like debris in fresh fluid was the cause. See photos on pg. 3
//Retrospect
Filter fresh fluid.
Bleed one corner at a time.
If you are going to clean out your AHC pump filters, make sure you notate how the gears are clocked and put them back in exactly the same.
Before reassembly, fill pump head with fluid as much as possible.
Our comrades in Russia run fluid that looks like cigarettes are put out in it and repair AHC lines by hand - this system can take abuse. There also might be one more mystery at play here with these failures.
//AHC Detail
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