Connecting master brake cylinder to proportioning valve

Hi, thanks for quick reply. We have Corvette calipers in front and original drums at the rear. New master cylinder and proportioning valve, all lines were bled out. Master cylinder bench bled, rear brakes adjusted tight. Car brakes on the front but rear wheels keep turning. I see many pictures online of pipe routing, and start doubting how we have routed it.
The picture is how it is routed now. But should I cross the lines an change ports?

Vennlig hilsen

Knut Smilden

Good morning,

I did not see it in English but I will tell you one thing, the large line out of the front goes to the front calipers. The other two lines out the rear go to the rear brakes.

is that how it is plumbed?

The fact you have no pedal leads me to believe you still have air in the system or a bad master cylinder.

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Do you have pressure to the rear brakes?

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

Roy

Hi Roy. The 1/4 inch tube goes to the rear. The two 3/16 to the front. When we bleed, there is good stream out of all bleeder screws, and the pistons in the wheel cylinders in the drums move. But the rear brakes will not hold when we brake. So maybe I would try to cross the lines from the master cylinder to the proportioning valve. I have seen pictures of that.

Knut

The master cylinder and the proportioning valve are new.

Knut

New or not, it may be a bad master cylinder.

No, I would not cross the lines at all. That will affect braking and could cause pulling. this is a bad idea.

I would find someone with a pressure bleeder to force fluid through the lines. You could still have air trapped in the lines.

Roy

Okay, so not cross lines from master cylinder to proportioning valve. I will look for some more air.

Thanks,

Knut

Just a stupid question. Did you mount the calipers with the bleeder valve at the top? You can put the caliper on and if the bleeder is at the bottom, air will not be bled out.

Roy

Bleeders are on top.
Knut

So in the master cylinder: the primary piston is the one nearest to the brake booster, and the one that feeds the front brakes?

Knut

Correct.

Roy

But there are many pictures online where the line from primary port goes to the port on the proportioning valve that feeds the rear brakes?

Knut

That is why I stated the big line goes to the front brakes and the smaller lines go to the rear brakes.

On disc/drum the primary brakes are the fronts.

Roy

But the primary are to the left on the picture, and those to lines go to the front. Is that not right then?

The large reservoir in the master is for the front brakes, so the line that comes out goes to the front brakes. The smaller chamber goes to the rear.

No matter what, you should still have a pedal. This will not prevent you from having a good hard pedal.

Roy

Sending you picture of the old master cylinder and proportioning valve. Are the ports correct "named"?

Here it is.

Knut

Yep, that looks good.

Roy

Thanks, then I will change to the old proportioning valve, witch by the way, was connected from secondary out port on the master cylinder, to the outlet port to rear brakes on the proportioning valve.

Got it. See if you can get a pressure bleeder as well.

Roy

Will do.
Thanks Roy.

Regards,
Knut

You are welcome.

Roy

Hi again, now I have routed the lines from master cylinder to prop valve the way I believe it should be. I am bleeding the system now. Can you confirm that this is right, as you said last time? It is a 1987 Camaro with disks at front and drums at rear.
Thanks,
Knut Smilden

Looks good.

Roy

Found this diagram for you.

Roy

This is not the valve we have. We have the original GM third gen F body valve. What concerns me is if I got the rear brakes plumbing correct. I think that the feed from the master cylinder should go to the port on the underside of the valve, then it gives pressure to the seal on the small piston and spring inside the valve, forcing the piston to move and let the brake fluid pass to the out port on the top, and to the rear brakes. If the feed from master cylinder goes in on top, the pressure comes on the wrong side of the seal, and will not have any effect on the piston and spring.
How do you see it?

I am sending you a video I made. Prop valve plumbing.
Knut

Here is a video I made: Brake lines from master cylinder to prop valve.

Okay, I will be here for it. The picture I sent you was for the 1987 Camaro.

Roy

Yes, the one on your picture fits our car, but EE use the original.

The inlet for the front is at the top. The ones below are for each front side.

The inlet for the rears is on the top as well.

Roy

I do not know if you see what I mean. I have got the front.
But I think the pressure to the rear brakes on the piston and seal should come from the correct side of the seal, where the lip is. And that is in the port on the underside.

Knut

On my video, the red piston, there is a black seal with the lip facing to the right. There is a small hole just under there from the brake line, and on top, the hole to the out port and brake line is to the left of the seal. So when applying pressure , the brake fluid will press the seal and piston to the left and let the fluid pass and go up to the outport and to the rear brakes.
That is the way I see it in my head.
Knut

I understand what you are saying but I am not an engineer and take the word of the information systems that I work with.

Roy

Okay. Anyway, brakes are bled now. It is getting close to bedtime here. I will try the brakes tomorrow and let you know the outcome.

Best,
Knut

Sounds good.

Roy

Hi Roy.

The car is in a garage with the rear end on jack stands. It is stripped for paint, and I cannot drive it outside for a brake test. It is maybe not ideal to test the brakes in this condition (with the wheels in the air). I have got a pedal now, but rear wheels are hard to stop completely. The car has a limited slip differential, and I think the rear wheels go separate ways when they are not on the ground. Maybe it is harder to make them stop then. Just a thought I have.
And when I brake, and the rear wheels turn, there is this " click clack" noise. Sounds like the brake shoes are moving around in there. Maybe (I think) because one wheel is going revers way, and not having the primary shoe initiate braking.
Do you have any thoughts on that?

Knut

If it was a limited slip, then both wheels would turn the same way.

It is not a good way to test, I agree. I would also make sure the rears are adjusted correctly.

Roy