Hard brake Pedal

I recently upgraded to front discs using the M1D brackets and nova rotors. Ive been driving the van the past few days and they've been working really well. While driving the other day, the pedal started to feel harder than it did before with what feels like more effort to stop. Still stops fine, but doesn't feel as nice as it was. It only seems to happen when Im moving however…after I come to a stop and pump the brakes while stopped, it feels like it did before.

No leaks in the system, master cylinder is full and everything is bled.

What should I check for? I plan on checking to see if the pads are still seated on the calipers correctly, maybe re-bleeding the system to make sure.

Thanks!

Think I figured it out…I readjusted the proportioning valve, and it's way better. Guess that valve is touchier than I thought, as I has tightened it down a couple turns on initial adjustments…

I am qurious about this.
Several things can cause this problem.
What you are saying about adjusting the proportioning valve dosn't make any sence to me.

What master cylinder are you using? Is there any free play in the pedal? You need to look very carfully for this free play and make sure the master cylinder piston is fully returning to its idle position. The brake pedal should move about 1/8 to 1/4" before the piston in the master begines to move.

Is the proportioning valve in the rear brake line? IF so where in relation to the master and other valves? And is it installed with the "flow dirrection" oriented correctly?

Did you use in line residual check valves? If so which ones and where are they mounted?

M1D

It all seems to be working great now….hmmmmm

I have the second gen master cylinder and I have about a 1/8" play in the pedal before it pushes the plunger. I have the rear brake line coming out of the MC into the proportioning valve, then through the 10lb valve. I have the front going through the 2 lb. Pretty certain everything is connected in the correct flow.

Hey Scotty, If it does it again , try taking your toe and pulling up on the pedal and see if that helps it. As close as the adjustment is , might be something as simple as drag on the pedal via the rubber washer or floor mat stuff on the floorboard not returning it all the way. It doesnt take much. The way the brake arm hangs out there decent return spring tension is a must.

Well, what Digz said because if the master does not returnto full idle position the pedal will get harder.
But thats not the only thing that can cause that.

Go for a couple good drives where you get the brakes hot and up to temp. A few highway speed and quick slow downs to cook things up.

If you no longer have the problem, Good.

If you do have this problem again I would have to say the the problem might be too may residual check valves.

I know some people run the 2nd gen master cylinder and think it fine but thats not my choice. heres why.

As far as I can tell the 2nd gen master has 10lb residual check valves built into both ports. Although I have seen some cheep ass rebuilt masters with parts like that left out. (that would be better in your case)

To start with 10 lb residual will be too much for the disc brakes which need 2lb, and will make them drag which will heat them and make the fluid expand more then normal, but only make the pedal harder if something else is wrong like any other valves having been put in backwards to flow direction or too many reasidual check valves.

The rebuild kit for the 2nd gen master shows residual check valves but that dosn't mean they get used for the 2nd gen. The only real way to know is to pull the tapered brass inserts out of the master cylinder ports and remove the top hat shaped rubber valves that may be in there.
(this is actually why I and every other aftermarked suplier recomend the early Corvettte master; because it does not have them)

It said by those experts who know, when two residual check valves are installed in a row, one becomes a multiplier of the other. This would mean if your master has a (not wanted)10 lb valve and you add in the needed 2 lb valve (2 X 10 = 20). you system will be dragging the calipers at 20lbs presure. this will lead to a harder pedal as the brakes heat up.

One other positive thing is, if the pedal is getting hard as it did, then you certainly have no air in the system. (good job on the bleeding)

Keep us informed how it goes.

Also which port are you using for the front and which for the rear on that master? there is a primary (for rear) and a secondary(for front)

look here
http://www.mpbrakes.com/uploads/documents/mcplumbingpdf.pdf
M1D

Interesting, I guess I will have to do some more test driving to see if that's what's going on. Seems like that could be the case.

I have the rear brakes going to the rear outlet and front to the front outlet. I had upgraded to the dual MC with my drum brakes before upgrading to discs and was going off Don's photos of the plumbing.

Maybe someone else with the second gen MC and front discs can chime in here and tell us if their MC had the residual valves already.

I guess it wouldn't be too much trouble to just check myself.

Thanks for all the info!

That's also a good point. I just want to make sure I have everything set up correctly and be able to stop safely and efficiently. If that means a harder brake pedal than Im used to, fine by me.

As I understand it, the hard brake pedal you are talking about ; Came on during a longer drive and went away at a later time. Is that correct?

The business of how you set the cam bolt will either increase the pedal rotio or decrease the pedal ratio by a small amount, I'm not sure if you would notice the difference on your foot, but technically it does change the mathamatical values.

I posted about that some where on this site.

M1D