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Had a great day with 13pt bleed and saved locks til last.
Transverse lock bleed fine using UDT999.
Longitudinal lock producing in 3-5 minutes 1/2 teaspoon through normal bleed screw. So here is what I did thus far and need some ideas from you C4 chaps;
I see no signs of slave leaking. So, I said lets isolate the slave itself and unhooked brake line to slave, feed a few feet of old twisted pair phone wire to see if clogged line, all good. Bleed that open line with udt999 and still no change, barely 1/2 teaspoon in minutes?
Next, I wanted to try the incremental pulse test to lockup front diff, which is confusing? What does incremental pulsing the center diff slave got to do with locking left and right front Axles? It did not lock left and right wheels?
My concerns questions;
What does 0 vs L on solenoid valve device mean?
The solenoid valves, they are in closed position on ignition turn on?
What would cause longitude slave line to bleed so weak vs transverse slave?
I get a perfect Bomb and solenoid device bleed from bomb.
I am concerned about what is normal pressure to and out of solenoid valves in frunk to slaves?
Never had and don't have PDAs fault codes.
How does the bleed of locks output of both your locks compare?
Anyway to test the solenoid fluid volume output for each lock?
They should bleed the same. Take the slave out and make sure it's not seized.
If it's not seized. Try bleeding fluid through the hardlines ie, unhook it from the slave as you had, and make fluid flow through it. There are two pressure regulating valves right where the PDAS soft lines split to the two hard lines that run direct to the the Slaves. So look at that hardline that connects to the slave, on the other end of that line there is a pressure valve that could be clogged.
I did try the lock bleed with that line disconnected from slave and same as slave bleed, no throughput When you say, other end of line? Other end located? On right side of frunk, I have hard lines leaving the lock valves box (I call the lock solenoid valves) next to the PDAs big plug box in frunk, one from a port with an O and one with port L and they go about a foot to the frunk wall and have a coupler of some kind and continue into body ... All hardline ... Are these couplers in frunk what you are saying are pressure regulators? or, saying soft lines near the slaves ?
If I depressurize the entire system and disconnect one of the top ports from the lock valves box, am I gonna have free flowing brake fluid? I think the line out of lock valves box to slave is blocked? Trying to visualize where to disconnect in frunk and somehow clear line for another bleed test?
I am going to pull the slave eventually, it sure looks simple enough and I am curious
Go under the car and pull out the longitudinal slave. Make sure it's free to move back and forth. And then make sure the line leading to it is clear. Then- look at the connector where that hard line begins. It's a pressure valve that keeps the high pressure from traveling easily back through the system. Take that out and make sure it's clear.
What tends to happen is that no one over the last 25 years, other than a very few people who understand these cars, ever really bled the entire system. So with dot 4 fluid, over time,you get corrosion in the copper lines and yu get crystals building up in the system. Things get gunked up and slaves seize.
When yu use the udt- you should be getting a ton of fluid out through the slave.
If you can't find it after all this...if you want to get crazy, you can cycle dot 3 fluid into the system, drive with that for a while and keep bleeding with that for a time. And then switch back to dot 4. The dot 3 will help to dissolve the crystals and unclog the system.
Oh you're good.... Anxious to check tomorrow. I was also trying to determine which is which of the lines leaving solenoid in frunk goes to which slave? Tried touching the valves while pulsing and couldn't tell as vibration in both lines.
This is some good info as I'm about to attempt a full bleed on my c4 as well. Assuming everything goes smoothly, roughly how many hours am I looking at?
Well, the mystery continues... Found the pressure fittings... I undid the bottom section after undoing the hard line that goes from the slave.... Interesting, I thought I saw gunk, no gunk, just a piece of plastic that flexes and moves up and down... Findings;
Fluid free flows from frunk and no blockage through to this undone fitting... Gave my motive a few pumps and steady stream of fluid to drip pan I had below.... Forgot if with ignition at 2 or completely off... Begs the question, are solenoid valves open as default? Anyways, back to my slave not bleeding ... So, this narrows the blockage to section after pressure fitting to slave input line...
I found a ball bearing on the ground when looking at pressure fitting that must of dropped out when I undid fitting? Does this sit on top of plastic piece on end of fitting?
So, the key from slave did not fall into my hand as I had hoped may have to soak in PB and keep at it....
More that one way to skin cat? I may reattach pressure fitting without bearing and open line at slave and try and push fluid to that point with motive. If free flow to that point I will put bearing back in pressure fitting and do normal bleed, if no flow, I will be really puzzled...
Hold on...there is no bearing in the fitting on the line. Can you post a pic? There are also no plastic pieces in the fitting I am talking about...
Hope we are talking about the same thing.
That thing that holds the front diff lock in doesn't "fall out" in your hand. They are a bitch. It does come straight down, and you are in California, so you may have it easy, but I usually find I have to soak in pb blaster and tap back and forth till it starts to budge...
Oops, photo is not of actual rear passenger side and off Web, not my wrenches. Circle just indicates to you the fitting I undid, just the bottom half of the two pieces. Is this the pressure type valve you mentioned? I will take photo's of pieces when undone again. Car won't be started while work being done.
Attached is an image from rosepassion.com (handy for sharing PET diagrams) that should make the descriptions a bit easier to follow. It sounds like you've narrowed the blockage down to the short line highlighted in red?
Slippery slope- I believe that the solid crud in brake fluid lines comes from the mixing with the water that the fluid absorbs. It seems to really accumulate at the pdas slaves for some reason. If you have a line that is that filled with crud, then the pdas locks are probably not doing to great either. A flush helps, but the slaves need to be opened up to really clean them out. Rebuilding the slaves is straight-forward with Colin/9m's kit. The transverse lock is especially easy to pull off, the longitudinal lock can be a pain to wiggle free. At least something to tick on your to-do list if not now.
Great drawing. Yes, the opposite slave of red, but that section of a few feet of line from pressure valve to longitudinal lock. I circled the wrong valve, it's the one right next to it. I do see a few crystals around longitudinal slave. Any ideas on how to exactly clear that few feet of line ? A Jig for air compressor? Scrape wire? Phone wire to flimsy to follow bends.
G., about the key, just the one Allen key removed and PB and tap key left and right a bit? So, the key does not pull towards apex of triangle part, but straight down to ground?
Nick,
I do have the 9m kit, was waiting for a noticeable leak on either slave and never saw one.
Appreciate the input. Stay tuned, hope I can get that key loose.... I do have a heat gun, anybody resort to that?
Epiphany, was trying to do all this laying under car. How about I remove that small section to the bench and figure it out
If I want to buy a cap or plug for temp ose while open Brake line, does anyone know the thread I am after? My search says, lines are 1/4 inch and male thread fittings are 7/16 -20 ... Sound right?
02-27-2016, 09:45 PM
PDA longitude slave not bleeding?
When you say, other end of line? Other end located? On right side of frunk, I have hard lines leaving the lock valves box (I call the lock solenoid valves) next to the PDAs big plug box in frunk, one from a port with an O and one with port L and they go about a foot to the frunk wall and have a coupler of some kind and continue into body ... All hardline ... Are these couplers in frunk what you are saying are pressure regulators? or, saying soft lines near the slaves ? 
