Rear brake issues

[~MoMo~]

Having some issues passing inspection, failed on weak rear brakes.
Have a 98 gt-t spyder, non-abs.

While brakes are depressed, rear wheels can be turned (barely) by using a breaker bar. It gets heavier to turn with brake booster operation (engine running), but I can still get them to turn slightly.

What I have inspected/replaced:

* Inspected for leaks, none found
* Verified brake booster operation
* New calipers on all 4
* Bled brakes, following service manual procedure
* Replaced proportioning valve mounted on firewall
* Replaced master cylinder
* Measured clearance between master cylinder piston and pushrod, was 0,7mm and service limit is 0.6 - 0.85mm I believe.
* Brake discs within service limits/thickness (about 1k miles on them).
* Semi-new brake pads (about 1k miles), removed glaze with sand paper.
* No bent or damaged brake lines

Now what the fudge?! There's not much else to this brake system, I'm beginning to think the rear brakes are working like they are supposed to? Can anyone check/verify if it's possible to get the rear wheels to turn (ever so slightly) while applying the brakes?

This is driving me nuts

 

[Dsm Rob]

Have you replaced the brake hoses?

 

[johnb5784]

Have you replaced the brake hoses?

try what he said. the rear brakes in my spyder do not turn at all

 

[jtmcinder]

Besides the hoses - which was a good suggestion - I can't see what's left. But if they really inspect this, you could get pressure gauges (and the adapters for brake-lines) and measure the pressures. The cut-off and slope for the prop-valve are somewhere on this site or in the FSM; armed with these data, you can verify if you have a pressure-delivery issue or if it's in the calipers/pads/rotors.

I know for sure that on my Evo I cannot turn any wheel when someone is on the brakes, but, then again, I'm not particularly strong and the Brembos on an Evo are rather different from the floaters on a DSM.

 

[Dsm Rob]

When you crack the bleeders does a good amount of fluid come out or does it dribble out?

 

[~MoMo~]

I get a good steady stream when bleeding them so it doesn't look like a delivery issue.

So next is replacing the brake hoses. Weird that both sides are equally bad though. Do you think I'm experiencing pressure loss in the rear from flex in the hoses?

Ok so I had an extra SS brake line for my 3000GT laying around, turns out it's almost 100% identical to the eclipse (rear). Installed it on the right rear wheel, bled brakes and no difference. Could still turn the wheel with a breaker bar.

I guess I should have replaced the front left brake hose too, since those wheels are linked but I didn't have any available. Not sure that would have made any difference though?

The previous owner replaced all calipers, the rear have the number 762 on them, what are they supposed to be? I'm running out of options
The only thing I can think of now is if there's some sort of malfunction in the brake pedal assy and/or booster pushrod.

Poked around the brake pedal assy today, freeplay was within spec and pushrod engagement was great. Adjusted the freeplay to 0 just to observe any changes in brake force, gained zero so readjusted to spec.

Removed R.rear caliper to observe piston movement, with the brake pedal to the floor the clearance between pads were 0.7mm, my rotor is 10mm. Should be clamping good enough.
However, the pedal is about halfway to 3/4 down when applying max brake effort when everything is mounted, maybe that isn't enough pedal travel to move the rear pistons enough that they will lock the wheels? If that's the case I guess I have a volume/pressure issue going on with the rear brake lines.

Any input?
I'll paypal $20 to the person who solves this