Excessive Brake pedal travel before "bite"

[dj_v70]

I don’t understand what the vacuum pump would have to do with it unless the issue was only when cold start.

I had this same exact problem a few years back on a Toyota, it was the pin/slides. Mine were in the front. My guess is that OPs issue is is in front also as the fronts do most of the work and would be the most noticeable. (ie. lots of pedal travel before braking).

If it is not the pin/slides, I’d look at Jimmy57s. recommendation regarding bearings.

Good “Bite” is usually quality pads and turned rotors.

[800artfreed]

Any Solution? Thanks.

[justanotherhumanoid]

So I was waiting until this was fully resolved before posting - but since it might be a while, I should probably update this; long story short, I've done (almost) everything except cycling the ABS with VIDA and replacing the master cylinder. I believe it's one or the other, and I'll try cycling the ABS and bleeding the brakes again before I replace the master cylinder.

Here's my process of elimination:

1. Replaced all 4 brake calipers/rotors with R brakes (used new pins, springs, pads, rotors, even replaced the dust shields and gaskets where applicable). So it wasn't the slides or springs on my old brakes, issue persisted through the change (i.e. I stop faster when I stomp on it now, so it's a little better, but there's still that region of nothingness in the first few inches of brake pedal movement that I dislike).
2. Changed to SS lines (though it's very unlikely that squishy brakes are line related, did this anyway).
3. Replaced the switch and vacuum pump with new per XC70Rider's suggestion, also replaced and/or leak checked all vac lines.
4. Completely flushed brake fluid during bleed of new brakes (though did not cycle ABS while doing it, on purpose to check it this was the key step).

So I've got VIDA and a replacement master cylinder on hand, I'm just away from my car at the moment, so when I get back I'll cycle the ABS, bleed the brakes again (once or twice), and then test. If that fails, I'll replace the master cylinder and test again. I was sure that replacing all the calipers would do the trick (thinking it was the pins/slides/springs per forum suggestions), but apparently not.

At this point I'm also wondering it it isn't potentially something to do with the pedal linkage/rigging. I'm not too knowledgeable on that, is there some way to just move the linkage so that pressure's applied to the brake booster/master cylinder earlier in the pedal travel? Can I just remove the "dead space" by shifting a connection point somewhere?

If ABS cycle/bleed and Master Cylinder replacement don't change anything, then I'm down to the rigging option or Jimmy57's wheel bearing issue. How should I inspect the wheel bearings to rule them out? They seem fine, no noise, 100k mi on the car, spin by hand smoothly. Not sure what else to check there.

[Georgeandkira]

I too like nice, hard brakes.

My '76 Ford E100 van had 100% no-play, instantly contacting, perfect (swear word) brakes.

While doing front rotor replacement and a rear pad slap on a neighbor's Chrysler van we chatted. He complained that the van and every car he's ever owned had distressingly soft feel.
Apparently the disappointment is common.

If everything else in in order perhaps installing "bulge-proof" braided steel hoses is all we can do?

[justanotherhumanoid]

Yeah, that's what I want. I will get this car there, eventually.

Already switched to the steel lines when I changed out all the calipers, no change. =(

[abscate]

Sometimes this occurs when people use “ racing pads” or pads that promote “ low dust”

Akebono pads seem to be well received as do OEM Volvo of course

[ljsommar1]

I am a fanatic about doing all the maintenance on my vehicles but when presented with the same problem, I finally took my wife's Winstar to a shop. They bled the brakes while commanding the ABS valves open.The result was a nice hard pedal. They told me that a fair amount of dirty fluid came out even though I had bled the system several times. According to them this happens all the time .
I would not throw any money at this until I was certain there was no air trapped in the ABS system.
Good luck.

[justanotherhumanoid]

abscate, I installed Akebono pads over brembo rotors from FCP per forum recommendations when I did the replacement/upgrade (since I had some mid-grade/cheapish autozone stuff on there before). I was trying to kill all those birds with one stone, but the problem persisted, so in my case I don't think that was it.

ljsommar1, that's next on my list - I have a pressure bleeder, VIDA, and an extra liter of OE brake fluid. The exact technique of bleeding the brakes with the abs valves open I'm unsure of, though. So I can kind of lock them open with VIDA and then do a regular bleed routine? I thought I'd have to power on the car, cycle the ABS with VIDA a few times, turn off, and then bleed them, maybe do that once or twice.

Encouraging that the procedure solved the problem though. Your shop doesn't happen to be in the SoCal area, does it?

[MoVolvos]

*
I found by pressing the piston fully into the caliper will remove contamination that otherwise wouldn't just by bleeding. Allowing it to fully extend and then pressed in each time will also help unbind the piston. If there is rust during the initial bleeding the caliper could be binding requiring more pedal pressure or distance before grabbing.

*

[chrism]

If the pedal travels a shorter distance with a quick panic jab vs a slow and easy pedal application, that can be an indication of a master cylinder issue. (The piston seals seat more firmly against the cylinder wall when there is a “sudden” rise in fluid pressure against the front of the piston.)