Help - AHC problem while changing fluid (1 Viewer)

Snafu13F

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On the road update. After about 60 miles the check ahc came on again. At my next fuel stop I hooked up techstream and cleared the 1763 code. When I restarted it, I heard the pump cavitating. At this point I’m not sure if it’s a pump issue, air in the lines still or maybe even a small leak.
I did a quick bleed at the 4 corners, but I’m unwilling to mess with it until my trip is done.
 

grinchy

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Those square plugs are from Satan. They have itty bitty crimp releases in the corner but to crimp with enough force you have to be too close to the secured part so there is no room to push them out. Cut and replace much more sensible
On the road update. After about 60 miles the check ahc came on again. At my next fuel stop I hooked up techstream and cleared the 1763 code. When I restarted it, I heard the pump cavitating. At this point I’m not sure if it’s a pump issue, air in the lines still or maybe even a small leak.
I did a quick bleed at the 4 corners, but I’m unwilling to mess with it until my trip is done.
You had the pump out and cleaned the pump intake. But it sure sounds like a starvation issue.
 

Snafu13F

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Made it home. Back is practically on the bump stops. I had to reverse the pump several times to get enough flow the raise the front tires via accumulator. Otherwise I’d still be on a hilltop in TX. Raising the rear worked once but the last day was a complete no go. Current plan is to bleed the entire system one wheel at a time 3-6 times, ensuring absolutely no air in the system. i haven’t been able to detect any leaks, but I’m going to follow each line and double check the shocks while I’m at it. If that fails, I will pull the pump and bench test it along side the new pump I have. I’m also planning to retest every system in the ahc active test menu, it’s possible I missed something my first time through. If nothing else, I’ll be an ahc expert by the time I’m done!
 

Snafu13F

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So I’ve also just realized that the system behaves differently when the truck is on vs off. If I unplug the pump and power it directly, it runs without cavitating. Yet if I turn the truck on, it instantly cavitates. I think this is probably a key clue, but I haven’t figured it out yet. Any ideas?
 

radman

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Ground at the pump? Ground at the ahc computer (driver/left side third row behind the big plastic piece)?
A voltage regulator somewhere?


good call. maybe sneak some wire leads into the pump connections so you can check voltage with a multi-meter on while it's cavitating?
 

Snafu13F

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At this point, I don’t think there’s any issue with the pump itself. I spent some time bleeding the lines, and the system seemed to be working better. Today after a bleed, the pump randomly decided to cavitate. I verified the fluid level in the reservoir never dropped below the max level, so I pulled the pump and bench tested it again. No faults were detected.
I reassembled and the system worked perfectly, even going to high and back with no issue. I’m assuming I’ll need to bleed more, but I’m leaving it untouched until it acts up again. I think the lines are somehow depressurizing when it sits, which suggests a leak somewhere. No luck on locating that thus far.
here’s my latest techstream data pull. Numbers look wonky to my eyes. Should I bother with trying to manually level the truck?
D3A78399-2221-4718-8AA5-91571B1E5B27.jpeg
 
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Snafu13F

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I need some input. I’ve bled the system multiple times and am confident there is no air remaining in the system. AHC works intermittently. Yesterday I ran each test in active testing for the ahc and all of them passed, except for front/rear up by accumulator. Both front and rear rose continuously, but didn’t stop until the pump pressure exceeded the maximum threshold of 18.5. The system threw c1764 and c1765, which are the related codes for pressure. I’m slightly concerned the ahc pushes the vehicle up too high, there was more than 12 inches clearance between the top of the tire and the fender both front and rear.
Following the troubleshooting chart for those codes, the possible issues are clog in fluid line between the pump and no1 height control valve, clog in the no1 valve or the height control ecu. My gut says clog in the valve. Reviewing the video for the two times I pulled and tested the pump shows a significant difference in pressure.
Original test

Test 2 a couple weeks later
my theory is there was a clog in the pump during test 1. When I reinstalled it, the ahc functioned fully and rose back to N for the first time. I think the clog was pushed from the pump into the lines, ending up in height control valve 1. Which would explain its current, semi working state. It keeps the system at N for normal driving, only very occasionally throwing the c1763 code. I assume it happens because the system is constantly leveling itself. Clearing the code seems to work. If I attempt to raise to high, the rear quickly raises and then the front very very slowly does. It reaches H, but then throws the c1766, which is the failsafe for the pump running for 135 seconds. Again, clearing it resumes normal operation.
My problem is, looking at the valves location, I’m not confident I can remove this part. The fsm shows removing the muffler for access. There are 5 separate hydraulic lines on top of the bloody thing that even if I can access enough to get them out, there’s no way to get them back in easily. I’m also leery of taking the valve apart to clear the clog and reassemble. I’m not in a financial position to take it to the dealer, and frankly, I know more about this system now than and Indy will. So I’m at a loss on how to proceed now. I’m all eyes for suggestions.
 

bloc

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Is the pump still making the cavitating sound?

And yeah.. whoever posted the short 200 production videos.. one shows an AHC equipped cruiser on the production line without body yet. The hydraulic lines everywhere are insane. Total rat's nest.

Sorry I don't have more to suggest. Still watching, this is quite interesting.
 

Snafu13F

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It cavitated once after a bleed, but a simple pump reversal cleared it up. Otherwise it sounds fine.
Does anyone have a broken pump they would be willing to part with? I need to replace one of the power connectors, and it’s a unique and unavailable part.
 

radman

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It cavitated once after a bleed, but a simple pump reversal cleared it up. Otherwise it sounds fine.
Does anyone have a broken pump they would be willing to part with? I need to replace one of the power connectors, and it’s a unique and unavailable part.
have you connected with @GJamisonUT?


 

grinchy

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I’m all eyes for suggestions.
grasping at straws here, but I think your diagnosis seems pretty good. Behavior certainly could be consistent with particulate/clog.
If you have a vacuum brake bleeder you could try to suck the fluid back out of the valve from the pump location. I think I like this option best and it has a good probability of getting the particle. Of course you'll be stuck replacing all the fluid, and I don't know if there are any parts of the system that could suffer from a reverse pressure.
Failing this try the old tap tap on the valve? Get out your hot air paint peeler tool and give it some heat? Heat and tap tap? Maybe it'll jostle it out of the valve and further on down the line. Problem is, the next constriction location might be worse? Or maybe it'll go harmlessly into the shock and sit there . . .
 

ramangain

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One thing I noted when I bled it, the passenger rear had so much air in it that it looked like foam. Still trying to find the procedure to remove air from the system, which I’ve seen referenced, but can’t find
I'm late to the game here, sorry, I'm a 100 guy who is visiting the 200 tech forum to bone up on knowledge before I purchase.

The "foaming" is also a classic sign of a bad globe. Since you have a recurring issue with your pump, *perhaps* it is related.

How old ARE the globes BTW?
 
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have you connected with @GJamisonUT?


@Snafu13F I have yet to pull the reservoir and pump from my 570, but if you're interested PM me and we can work something out.
 

Snafu13F

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I'm late to the game here, sorry, I'm a 100 guy who is visiting the 200 tech forum to bone up on knowledge before I purchase.

The "foaming" is also a classic sign of a bad globe. Since you have a recurring issue with your pump, *perhaps* it is related.

How old ARE the globes BTW?
Original globes as far as I can tell, so 9 years. The ride is pretty smooth when the system is working, so I’m trying to avoid replacing globes if possible.

Is the actual AHC pump and/or motor carryover from the 100 series? Maybe not the mounting bits but the functional bits. If so, hit the 100 series tech forum, some folks on there may be able to send you a unit for testing.

It’s a slightly different pump unfortunately. I looked in the 100 forum and saw their pumps have screens internal to filter. I disassembled mine, there are no screens in the newer pumps. Go figure.
I’m on the road this weekend, so I’m taking the tools I need to keep it functional with me. When I get back, I still have to figure out what to do about that height control valve that likely needs pulled and cleaned/replaced. Just not confident I can do it.
 
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Snafu13F

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Postmortem and final thoughts. I believe my clog hypothesis was correct. I also believe that it FINALLY self cleared on my last trip. In order to navigate my driveway in Texas, H is required. On the first trip up, it took about 30 seconds, but the truck did make it to H without giving me an error. The next two days, it went to high in about 7 seconds. I tested it again today /and it takes about 7 seconds to get to high. Interestingly, it still takes over 20 to get from L to N, but I’m calling this issue solved for now.
side note for people working on the bumper and passenger rear wheel well. After cutting those stupid square clips off for a second time, I realized you can just install them in the receiving piece. The screws are more than sufficient to hold the liner in. I can remove the entire piece including the mud flap in about a minute now. I highly recommend making that change if you find yourself needing access more than once. I ordered These clips. They fit perfectly.
Thanks to everyone who offered suggestions throughout my saga, I very much appreciate you and this community.

George
 

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