One year later, I finally fixed it. Long story short, it was the return valve, as recently discovered by
@suprasvobodea in
his own struggle and
@LX470YYC in his.
I must say that the return valve is a new angle that I haven't seen discussed much before and might be the culprit for a bunch of issues reported throughout the years.
I have ignored it all this time pretty much only because it is under the bracket that holds the reservoir in place and I had a
very stuck bolt holding it. Always removed the reservoir together with the bracket, which also made removing the pump cover a minor inconvenience. I also figured my issue is with fluid coming out of the assembly, not going back in. WRONG! Bad return valve prevents the pump from properly pumping.
I had found a workaround where running the motor backwards (swap + and -) allowed the system to work for a short while (from minutes to hours), that got me going for waaay too long time. Probably moved blockage around in the return valve.
Before that I had to replace front passenger shock (hydraulic ram) - mine suddenly snapped couple of months ago, also a first, from what I have seen. The amber plastic bits came from inside, I guess some kind of a collar or a stopper. A completely destroyed bushing and lots of shims. Driving around with failing AHC, often on bump stops, especially in the front might have had done that. Hole in the upper part is where I had to stick in a large scredriver to prevent it from turning, to be able to unscrew the top nut.
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I also had broken bleed nipple on the accumulator since I got the car. I have a spare accumulator and made several attempts to remove mine, but **** those 2 bolts on top of the frame rail. Then I tried to drill out the old nipple and remove it with an easy out drill bit - no dice, it was super stuck. Finally went in with a 6mm drill bit and then tapped it with 7mm (original nipples are 7x1mm thread) - there was no trace of the original nipple or any boundary between it and the accumulator body, it was 100% fused! Removing the front globe and unscrewing the lines is essential to have the space to work and drill in a straight line.
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I was kind of nervous about drilling into the pressurized accumulator, but figured if you go small, it should be fine, so I drilled with a 2mm first. Eventually fluid started spraying out. I stuck a tube to it to collect it in a bottle and not make a complete mess of the entire front drive side.
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Eventually tapped the new thread, screwed the bleeder from the spare accumulator and of course, it leaked like a sieve - the nipples rely on a very tight fit between the nipple bottom and the seat in the body and of course drilling and tapping destroyed that.
That's when I found out that there are bleed nipple repair kits. Essentially an oversized seat with a nipple. So I went ahead, drilled out the opening to 9mm (there is plenty of material there) and tapped 10mm thread. Screwed in a 10mm seat with another 7mm nipple. The accumulator material is super tough and working space is limited, coupled with laying on your back, so thread was sloppy, but with plenty of thread sealer/glue it is holding up nicely. For the first time since owning it, I could finally bleed the accumulator.
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I also threw in some new globes from Impex, levelled side to side and for the first time in almost 2 years and half of South America later, I finally have 100% working AHC!
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I will be honest, the last month or so I was more or less ready to pull the trigger on a nice set of adjustable shocks, like Icons or Kings and send the AHC back to hell, but after driving at 50mph through some speed bumps in Comfort yesterday with the body barely moving, potholes that I can't feel and then some tight country roads in Sport with the body staying level, even with the RTT counterweight on top, I am a believer again!