Strange brake issue
 

I didn't see a specific brake sub-forum so if this isn't the place for this question please move it. Anyway I change pads and shoes and go to flush the brake fluid and bleed. I go in the honda tech manual suggested rotation.

Bleeding with a vacuum pump and trap, and this is not the first time bleeding brakes.

Rear right
Front left
Rear left
Front right

The Rear Right and Front Left bleed as expected and are done quickly.

Moving to the Rear Left it just doesn't bleed very well but I get some fluid flow.

On to the Front Right and it just doesn't want to bleed at all, I can pull 25" Hg vacuum and it wont even flow fluid to the trap.

And, of course, the brakes are horrid now and the car is not safely drivable...

I traced back to hard line and checked for fluid there and to make sure the flex lines wernt collapsed or blocked and they wernt.

I could see nothing wrong with the master cylinder or the proportioning valve but I haven't specificly on Honda brakes before.

Any suggestions or solutions before I trace all the way to the MC?

I've heard of the bleeder port plugging w/ rust. Might be time for new bleeder plugs.

You might try bleeding by pump/release bleeder plug. This might "blow-out" any rust build up on the bleeder.

good luck

Texas is right, bad bleeders.
I have had it happen to me a few times.

Good suggestion but I had already checked both of the ones I was having issues with as well as confirmed flow (all be it air....) through the caliper. Im not sure if the proportioning valve could be damaged or causing this problem or not. I will probably check that then check the pressures on the individual lines out of it and the master cylinder.

So you backed RF bleeder completely out and no fluid could be pumped out? This suggests corrosion blockage inside the brake line.

It might help to pump brake fluid through the brake lines from master cylinder to displace trash to ends. I would sequentially disconnect the brake lines from the calipers to avoid pushing any trash into calipers.

good luck

I don't see this being a proportioning valve because it happens on one front & one rear. Front brakes don't flow through the proportioning valve.

The 2 that don't bleed are on the same (diagonal) circuit. So maybe some problem with the master cylinder?

It's a bit strange for this to happen on diagonally opposite corners, but check for plugging in the rubber part of the brake hoses. If those are original, they're 20 years old.

I wasn't sure how the proportioning valve was laid out, the shop manual didn't really cover it...
I have found one other post on a different forum that described the same issue but had no replies. I am thinking either line blockage or master cylinder problem, Ill disconnect the problem lines and test for pressure and flow through and Ill get back.
Thanks for the help too.

So after digging into the issue more and studying the factory shop manual I determined that it most likely was the master cylinder having a failing secondary valve. So I unhooked the secondary line which controls the FR and RL brakes. Then pumped the brakes, the first two pumps I got spray which I expected, then just air. After letting it sit for 20min I got spray again. So it looks like either there is a blockage in the cavity leading to the secondary valve or another unknown valve issue.
Regardless I just replaced the whole unit for $45 with a lifetime warranty part, bench bled, installed and bled the lines and its good to go!

Thanks again for the suggestions and hopefully this can help diagnose this problem for someone else.

Thanks for coming back with the rest of the story. Lots of folks just dissappear and we never find out how they fixed it.