I've replaced all brake lines, flex lines, brake fluid and the master cylinder. All calipers, rotors and pads in good shape...operating correctly.

The problem is squishy brakes. I have to double pump the pedal to get the best braking. Also, when I first start the truck, there doesn't seem to have any braking power at all...until it's been running for a few minutes.

If I brake hard and suddenly...soft as hell!

Is it possible the power brake booster is defective? How do I figure that out?

Thanks

 

When you say that "it doesn't have any braking power at all" on startup, do you mean that the pedal is hard to push, or that you can push the pedal all the way down and nothing happens?

 

Did you do the power bleed or just regular old fashioned bleed? Sounds like the latter... You'll need to activate the ABS pump to get a full bleed, unless you have other problems which is entirely possible.

You can activate the power bleed (ABS) either with a diagnostic tool, by jumping the relay, or by putting the vehicle in low range and using the HDC function. All methods well documented here.

 

What I mean is that the pedal is the same softness, but doesn't seem that the pads grab the rotors. Just seems weaker....It's only when I drive for a short distance that the the brakes start working. By short distance I mean maybe a mile...

 

Sounds not properly bled.

 

Consider re-bleeding as mentioned with the abs pump bypass - see pic below.
Also double check the calipers that the bleed nipple is at the top. I made this mistake with the rears as the rears are not quite as obvious as the fronts.

 

Anbran, Did you make any progress on the brake bleed? I'm in your same boat. replaced one caliper, new master and new SS lines. No pedal till 2 pumps, 3rd pump stops the car but nothing. Did you bleed the brakes with the ABS modulator. I've done 4 iterations of manual bleeds ABS bleeds with no improvement. I'm about to swap in a used ABS modulator to see if a valve is bad in my original ABS modulator.

 

A couple weeks ago after hooking up the battery and starting up the Rover I noticed a light hissing noise which led me to find a collection of dust and other particles around where the brake booster connects to the engine. Upon closer inspection I found the line was 90% snapped and sucking air.

Right now it's taped with electrical tape and my braking that I thought was bad due to age and mistreatment is suddenly amazingly responsive. I never would have seen the broken section had I not seen the collection of dust on the engine.

It's a quick-disconnect fixture so push the plastic outer ring (distal to the bit attached to engine, affixing the hose) toward the engine and the hose will come free. It is brittle but inspect it thoroughly. Do this while the engine is off otherwise it will try to die.

Edit: It's the line behind the alternator with the blue electrical tape and the orange disconnect.

P.S. Don't mind the engine being sunken in the engine bay, my engine mounts will be here Monday, lol..

 

From your picture it looks like the black plastic connector (to the left of the vacuum line you taped up) is broken off too.

 

That should be replaced with the PCV mod anyway.