Jetta brakes-bleeding

Jim B.

I did find that unlike the originals, the replacement calipers' bleeder valves were not at the top of the piston, so there was lots of air in there. I took them off and hung them with bungees so that the bleeder should be the highest point of the space inside the caliper. I tried to let them gravity bleed but after 30-40 minutes still nothing was coming out and it was getting late. So I pump bled them hanging in that position. The pedal still only stiffened up to about halfway down. With the engine running the pedal goes all the way to the floor. But FWIW the sticking and binding I noticed is not apparent when it's running. Pedal travel is smooth and very long.

If I weren't borrowing other people's garage and effort I'd set it aside for another try another day, but I'm out of time for this. There's air in there but it's somewhere that a gallon and a half of brake fluid pump bled through the thing apparently can't get to. I drove it home carefully late at night and the next place it's going is the garage across the street.

Parking brake works though. That *was* the original goal of the replacement.

Goes with my profession I guess. Understood in principle -- can't make it work in real life.

Thanks all, Peter (B.Sc.E. H> I been watching your issue and the only suggestion I have is "are you sure

Jim B.

Hmmm So do these calipers have larger pistons? If so that could explain the longer pedal travel. Or it could be an issue with the brake booster pushrod and the brake master too!

just thinking out loud. later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

Oh I do know what the tradesmen think of us and why. I wish I could build more, but engineers are so expensive that professionally you generally aren't _allowed_ to build anything. You can beg tradesmen for feedback, but they don't want to look silly either so they often just "make it work" and don't tell you about it, preferring to curse you silently. Even as a student, I couldn't get the manufacturing jobs I wanted, losing out I suppose to brawnier kids who weren't so likely to get caught thinking too much. Later on, temping between jobs, I was trying to get an agency to put me in for assembly at a frialator factory, and they wouldn't do it, not because they suspected I didn't know about electrical controls and SS finishing, because I did, but because they thought the ex-cons that ran the floor would beat the crap out of me. They might be right, but dammit I've tried to build stuff and people won't let me.

So I'll settle for mostly only getting my hands dirty on my own time and dime. A very slow apprenticeship... there's so much to learn.

Good day, Peter.

Jim B.

The replacement calipers definitely have larger diameter pistons. They also, as I mentioned, have the bleeders on the side not the top of the cylinder as the originals did. The folks I got them from claim that they're from an 87 GLI (can I confirm or deny this from evidence on the part?), and that any 85-89 Jetta/Golf/Scirocco rear caliper will interchange with my 86 GLI. Can anyone confirm or deny that? I have even been told A5000 2-piston calipers can be retrofitted here without killing pedal travel like this, although this seems implausible.

The booster pushrod was pretty loose when I was working on it. The professional that I handed it over to couldn't fix it by bleeding (I still need to triple-check that he accounted for the unhelpful position of the bleeders on the calipers), and when he went to look in the booster at the pushrod he says it fell out on him. So the booster's been replaced, and pedal travel is still apparently much too long. I'm hoping I don't need to change out my mechanic now as well. I suppose the pushrod could still be wrong -- on the first go-round I thought of that, but couldn't tell whether it was adjusted by spinning the whole rod (which appeared to do nothing) or just the acorn nut on the end (which I couldn't grab to twist) so I left it alone.

Only other suggestion I've had is to check the rear brake pressure reg for a bleeder.

Thanks, Peter.

Perhaps also the master cylinder on a GLI does not match the one on the drum brake models. AutoZone (i.e. the remanufacturer who supplies them) only has one part for disc or drum brake 86 Jettas. My sample of one VW parts counter says they are different. Maybe I have a m/c intended only for a GL on there. Anyone know if they're the same?

Good day, Peter.

The above two places mention a 22mm master cylinder possibly coming standard on some VWs, but this might be for the 1990-up Jettas.

Maybe you have the 20mm brake master with not enough fluid going to your calipers. :-( And you need the 22mm since you updated the calipers.

Just thinking out loud!

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

You could try safely clamp down on all of the brake hoses and see what the brake pedal feels like then. If it is very high and very firm, then you probably have a problem with the calipers or pads. Then you can release one clamp at a time to see if that makes a drastic difference.

If it is still going down too far then maybe it is the master or hoses. I'll still raise an eyebrow with the booster pushrod though!

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris

I skimmed thought this post so if this has been covered sorry.

I did a rear disc swap on my rabbit two years ago. I used rear calipers from an 88 Jetta. I swapped out the proportioning valve for Scirocco in lines, as well as a newer style 20mm MC and booster. After a month of bleeding (Pressure bleeders, Gravity, ect.) and going over everything I could think of someone suggested I flip the rear calipers over 180deg. I had originally mounted the rear calipers with the E-brake arm up. So I did as suggested and temporarily mounted them with the arm down. I installed a rubber line long enough to allow me to flip the caliper over 180 deg on both rears and re-bled the system. Only after doing this did I finally get a pedal. I recently replaced all the calipers, rotors, pads and upgraded to a

22mm MC on this car. I had the same issue until I flipped the rear calipers to relieve the trapped air. My only suggestion would be if your rubber line is not long enough to flip the entire caliper, use a C clamp to hold the piston. Just my experience. From VWsport.com NNTP Gateway

One note here that was probably just left out: don't clamp your good brake hoses, get some from a junk yard for this "safety clamp" test. If you crimp your hoses enough to stop the fluid, you will damage the hose and it will fail (in likely an unpleasant way). In fact, the weight of the caliper alone (while you change out pads for example) is a no-no if you go by the books, although I've seen it done.

-Arthur

Yes Arthur is right, clamping down on brake hoses is not a "recommended" thing to do in most cases. It was also a warning that Woodchuck mentioned too!

I do wonder why tools are sold to do this specific service? 8^) One of them here:

New hoses are not super expensive for your ride, and if you find one that has failed you could replace it or all of them. I hope that they are not swelling up and causing your low brake pedal problem. The hose shut off clamp (buy 4) and the hoses might even cost less than all of the brake fluid that you ran through your brake system! ;-)

BTW this was just a suggestion to isolate parts of the brake hydraulic system for testing purposes and I did mention "carefully". :-) later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris