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On my 84RS I rebuilt the caliper and filled it with brake fluid before attaching it back onto the fork. I had put a small wooden wedge into the end of the short hard line that comes from the flexible line. I figured I would have very little trouble bleeding the brakes because I think the system is pretty full.

First, I tried pushing fluid up through the open bleeder. I had it in a syringe. It didn't take any fluid. It was as if the bleeder wasn't open. Then I got out the vacuum pump and it did no good either. I am stumped as to what to do. I did check the bleeder fitting and it is not clogged.

Any ideas as to what I'm doing wrong? Or, do you need more specifics?

Chuey

Last time I had my caliper in bits I filled the whole system from the bottom using a syringe attached to the bleed nipple in the same way you describe and it worked OK. All the fluid has to get through that small return hole so the master cylinder piston has to be in the correct released position but the fluid appeared in due course in the bottom of the master cylinder reservoir though it did take a while. I didn't fill the calipers up first but I did push the pistons all the way back which effectively minimises the volume. If you hadn't already got some fluid in the system I'd suggest using the syringe to push air through the bleed nipple to make sure there wasn't a blockage somewhere.

Chuey,
Why don't you take a container, fill it with a few inches of brake fluid and run a hose from the bleeder into the container so the end is submerged in fluid. Open the bleed screw and hit the brake lever, if you see no bubbles you have a blockage, if you see bubbles, when you release it the lever it should suck fluid into the system. Pump it through a few times and after you close the bleeder, it should have come up somewhat.

I figured the system would be open from the bleed nipple up to the master cylinder but now that I think of it, it wouldn't be able to push past the M/C diaphragm and up into the M/C reservoir.

Chuey

SteveD wrote:Sounds like a blockage. Is the lid still on the reservoir?

No, lid is off. I'll start working on it again a little later today.

Chuey

Chuey wrote:I figured the system would be open from the bleed nipple up to the master cylinder but now that I think of it, it wouldn't be able to push past the M/C diaphragm and up into the M/C reservoir.

Chuey

With the brake lever all the way out, I'd expect the brake fluid to be able to return to the reservoir, if it was pumped up from the bleed nipple.
Watch out your cup doesn't runneth over.

ME 109 wrote:With the brake lever all the way out, I'd expect the brake fluid to be able to return to the reservoir, if it was pumped up from the bleed nipple.
Watch out your cup doesn't runneth over.

+1.
On my R100 front calipers I connected a large veterinary syringe full of fluid to the bleed nipple. As I pumped the fluid in the reservoir slowly filled to the top.

When bleeding from the bottom, you have to make sure that the line connection to the caliper is straight up so air rising to the highest spot in the caliper can exit through the line. Otherwise an air pocket is created.

Kinda makes you want (well adjusted) drum brakes!