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I've been working on the T/A trying to get it ready for it's first event of 2024 in May (details HERE).
I was planning on new pads for the front, and bleeding the system (old fluid was very dark). I should note that I was having no problem with the brake system...it was performing as it had since I bought the car 10 years ago. Good pedal, no pulsation, but lots of dust from these pads, and not stellar braking power (a too fast idle making that issue worse).
I've had all 4 bleeders soaking in Blaster for a few weeks, and was lucky enough to get them all loose without issue. Win!
Yesterday I cleaned out the master cylinder reservoir. Drained, cleaned, and got a few "floating" bit of debris when I started to refill it. So I cleaned it out again, and repeated this process about 4 times until I could fill the reservoir and the fluid remained spotless. Nothing unusual in my experience. (Level set: I've spent my life around automotive repair, and done my share of "regular" brake work (pads, shoes, drums, and discs, on-car lathe, pipes and hoses. Not so much with ABS and nothing regenerative or self applying. So I know a fair amount, but am not a line technician).
After the reservoir was clean and refilled, I moved to the passenger rear corner. Crack the bleeder open and the old fluid flows right out. Gravity bled until the fluid runs clear. Closed it up. I kept the reservoir full, never allowing it to run dry. So far, so good.
This afternoon I moved to the driver's side rear. Same routine....master cylinder full, lid loose, crack the bleeder open....and nothing. Opened it more, and nothing. Removed the bleeder. It's open, not plugged or corroded internally at all. No fluid. I reinstalled the bleeder, and with it loose, used a hand vacuum pump to try and pull fluid through. Nothing.
OK, so we have a collapsed hard line or hose from the body to the axle I'm thinking. But, if it was the hose, I would not have gotten any fluid from the passenger side. The hard line from the M/C to that hose at the axle must also be open. So I'm looking at the hard line from the distribution block on the axle to the wheel cylinder. Expecting to find it crushed by a jack or similarly damaged, I visually look at ever inch. No signs of damage. I run my hand over the whole length of it. Nothing.
I pulled the drum, just to take a peak. It's had rear brake service before (1 owner before me, about 52k miles on it when I bought it, 64k now). But all looks good. (There was brake dust in the drum, indicating that at some point since those shoes were installed, the brakes on that corner did work).
While I was lucky with the bleeders, looking at the lines, I'm not optimistic that there will be a repeat performance. I'm letting things dry (I washed out the drum and system components with brake clean), then I'll reassemble the thing, and try pushing fluid out with the pedal. I do not expect a different result.
So I'm down to removing and inspecting the 18-24" hard line on the driver side of the axle. Does this seem right to you? Am I missing something somewhere that I should check before I (likely) destroy that line to check it?
Last edited by DynoDave43; 03-18-2024 at 05:31 PM.
I'm seeing a DRY master cylinder in the photos. Which means, it now has air in it, which will NEVER come out, NOHOW. You could take it back in time to the day the asteroid killed the dinosaurs, and even if you had THAT LONG, you could run a gallon of fluid though the whole system EVERY DAY for 65 MILLION years, and TWICE on Sundays just for good measure, and that air will STILL be right where it is now, at the top of the MC, above the ONLY paths it has to exit: the fill hole (where the reservoir sticks down into it) and the line fittings, because BOTH of those things are BELOW the air.
Doesn't matter if you "think" you "never let it run dry": your photo shows that it's DRY. After that, ya gotta do what ya gotta do. Doesn't matter how you bleed the rest of it with it still on the car. Doesn't matter if you use a "vacuum" bleeder whether hand or power. Doesn't matter if you use a pressure bleeder. Doesn't matter if you use one of the most inexorable phenomena I've encountered since being assigned to this miserable pitiful universe (gravity). DOESN'T MATTER DOESN'T MATTER DOESN'T MATTER DOESN'T MATTER DOESN'T MATTER DOESN'T MATTER. As long as that air that you've allowed into the MC remains ABOVE all possible escape routes, it's STUCK right exactly there, and will NEVER EVER leave.
Looks to me like time for a MC bench bleed. Then AND ONLY THEN, proceed to further troubleshooting.
Doesn't sound to me like a problem with one of the hard lines. NOT saying "your hard lines are good"; NOT saying "don't change your hard lines"; NOT saying "hard lines don't go bad"; NOT NOT NOT NOT NOT NOT NOT NOT NOT. Please, keyboard warriors, don't accuse me of saying ANY of those things. All I said is, a hard line isn't likely to be the cause of THIS PARTICULAR problem. A hard line, to become "bad", has only 2 possible failures: a leeeeeek (I'm going to go out on a limb and assume the OP can recognize that), or a blockage (in which case no fluid will "bleed" out of the affected wheel cyls or calipers). They're STEEL and they're HARD; they don't "collapse". EVER. They leeeek or they get blocked, ONLY. Since we're not hearing about either of those things, the possibility of a hard line failure IN THIS INSTANCE, is negligible. Don't permit yourself to descend (ascend?) into the realm of the space aliens taking a break from creating crop circles and Elvis sightings because they're bored with all that, and they decided to visit THIS car and "plant" this "bug" in it (all of you that have ever taken a community college electronic tech course will know what I'm talking about) just to "test" these inferior humans' capacity for logic and reason; while that MIGHT be "the explanation", I'd STRONGLY suggest investigating all the REALLY LIKELY ones, especially the MOST LIKELY ones, first.
Which according to the photographic evidence is, air in the MC, requiring a "bench bleed".
after you follow the advice above, disconnect the hard line from the cylinder and you may find that it flows freely but the cylinder requires replacement. it's not uncommon for them to get gunked up and fail to bleed.
I believe Sofa that air in the master is likely the issue, though I would comment that your vacuum pump should come in handy to fix this issue. When I had the same happen on my car, I bought this vacuum kit, which has a wide rubber seal attachment. Using that, I was able to pull a vacuum on the master and sucked out the air that way.
As a note, if you do it the way I did, you have to achieve a HIGH LEVEL OF VACUUM for this to be safe. Pulling a vacuum will only increase the volume of the air in the master cylinder in proportion to the vacuum pulled. If a high enough level of vacuum is not reached, some air may remain in the master. For me, I pumped and pumped until the vacuum level stopped moving, let all the little foamy bubbles settle out of the line, and repeated until no little bubbles were left.
Sofa, I have to ask....I'm not saying that you are wrong about air in the master cylinder (your track record here on this site, and my experience with your advice give me too much respect for your thinking to not give your comments on this serious consideration) ....there may be some, but I have some reservations about that as I've used this cleaning method before without issue. With the system closed, and the engine NOT running (no vacuum boost), the pedal is very firm and steady. But if air is an issue, I'll deal with it as you have described. Let's set that aside for a moment.
Since the reservoir was cleaned, I have since refilled it, and gravity bleed the passenger rear wheel without issue. Open that bleeder, and fluid come rolling out. Top off the reservoir, and open the bleeder on the driver side, and no fluid. Literally, not one drop. Given this, and given that the LR and RR drums share a master cylinder bore, a metal line on the body, and a rubber hose to the distribution block on the axle, how can the problem with getting NO fluid out of the driver side be caused by air in the master cylinder?
how can the problem with getting NO fluid out of the driver side be caused by air in the master cylinder?
It can't; wouldn't have anything to do with that particular problem. Only the one where there's "not stellar" braking power.
More likely, that line is blocked with rust. Remember, just like the rubber hoses, the hard lines are steel; they too can rust inside and eventually get blocked. "Collapsed" isn't an option. For that issue, a simple replacement would do the trick. You can pick up sticks of brake line down at the corner parts store and bend em up to fit.
Brake fluid is hygroscopic, meaning, it attracts moisture. (unless you've completely converted over to silicone fluid) Over time the system inevitably gets water in the fluid. Equally inevitably, the unprotected steel and cast-iron parts all rust.
As also said, WCs are cheep, and once you figure out a strategy for dealing with the clips that hold em in, eeeeezzzzy to replace. Not a bad idea to just renew them. Might be eeeeeezzzier than trying to unscrew the brake line fittings from them without damaging anything.
After a couple of days of soaking with Blaster, the nut came loose from the wheel cylinder and spun freely on the pipe, so no damage to the pipe, which is good. Sort of a long thread on that connection, so it didn't happen right away like with the bleeder, but as soon as it was loose enough, fluid came out. So it appears the issue is with the wheel cylinder itself. I'm going to have to disassemble the old one to see what happened. Stopping at the parts store at lunch to get a pair of wheel cylinders ordered, and a pair of seals for the backs of the rotors on the front, so I can clean and repack those bearings.
don't throw out your old wheel cylinders before test-fitting the new ones onto the steel lines. and test fit them before installation.
There are two thread sizes, early and late, and I've had cylinders with the wrong fitting in the right box before. I've done a hasty re-build with the old housing and the new innards a time or two.
Your cylinders should be the later ones, change over was in 84'-85' ish. It's probably more likely to get the later ones when hoping for the early ones, which is what I encountered though.
Had the exact same problem. OEM fluid after 30 years on a completely original IROC-Z low milage. I ended-up pushing the brake pedal a bit with bleeder removed. It unjammed it lol. Fluid came-out after. Anyhow, I ended-up changing the cylinders since they started leaking after a bit.
Indeed. And the fitting style is completely different too.
Early is SAE threads and inverted flare fittings; late is metric threads and bubble flares. Changeover was during 84, so 83-back you can be sure will be inverted flare, and 85-up will be the metric bubble flare. 84, you have to pay careful attention.
Yes, ran into this at the parts store this afternoon. "The book" listed both an English and a metric wheel cylinder. I had her order the metric ones. I will test fit as best I can before installation, but there is no give in that hard line....it won't be easy.
I'm more worried about those wonky clips that hold them in. I have not read good things about them. Tough to remove, and even worse to refit, and often loose after you do. Appears they made a bolt on bracket for the earlier design on G-bodies, but that part is now out of production and out of stock. I'm not sure they fit F-body brakes, just something I was reading about.
I used to use a particular old destroyed screwdriver, that had just the right width and a bend in the tip, to get behind the clip and loosen it. And yes, a large socket, seems like it was about 7/8" or so, will pop the clip right back up on there.
Here's what the clip looks like, to prepare you mentally for popping it off. https://shop.advanceautoparts.com/p/...acd/11590055-P Real easy once you figure out about prying those tabs of the clip up over the lip on the cyl. (no idea whether this is the right cyl for our cars, just, it's the same type of retainer)
03-18-2024, 05:25 PM
This happened to me. If it is the wheel cylinder you should replace both, they are cheap enough. 
