2006 F-250 6.0 Power Stroke – Brakes Applying Themselves After Replacing Hydroboost & Master Cylinder

[FALKOR3theLuckDragon6.0]

Alright, I’m at a loss here and could use some input.
I’ve got a 2006 F-250 6.0 Power Stroke, and after replacing just about everything in the brake system except the ABS module, I’m dealing with a weird issue. After a fresh bleed of the hydroboost and master cylinder, everything feels fine at first. But after driving a mile or two, the brakes start applying themselves—not all at once, but enough to be a problem.

Here’s what’s been replaced:

Hydroboost (OEM from Ford)

*Master cylinder (Aftermarket from O’Reilly’s, since OEM is discontinued)

*Brake lines, calipers, and pads
Now, here’s where it gets interesting: if I loosen the two nuts securing the master cylinder to the hydroboost, the issue goes away, and I can drive it back home with no problems. That makes me think the pushrod might be preloading the brakes and possibly needs a spacer.
Has anyone dealt with this before using an aftermarket master cylinder? If so, is there a universal spacer that fixes this, or is there something else I should be looking at? Appreciate any insight before I start throwing more parts at it.
Thanks!

Edit: the problem started with replacing just the mastercylinder. It wasn't until after that I noticed the hydro boost was leaking in the cab and believed that to be the issue. Sadly it wasn't.

 

[6.0 Tech]

Alright, I’m at a loss here and could use some input.
I’ve got a 2006 F-250 6.0 Power Stroke, and after replacing just about everything in the brake system except the ABS module, I’m dealing with a weird issue. After a fresh bleed of the hydroboost and master cylinder, everything feels fine at first. But after driving a mile or two, the brakes start applying themselves—not all at once, but enough to be a problem.

Here’s what’s been replaced:

Hydroboost (OEM from Ford)

*Master cylinder (Aftermarket from O’Reilly’s, since OEM is discontinued)

*Brake lines, calipers, and pads
Now, here’s where it gets interesting: if I loosen the two nuts securing the master cylinder to the hydroboost, the issue goes away, and I can drive it back home with no problems. That makes me think the pushrod might be preloading the brakes and possibly needs a spacer.
Has anyone dealt with this before using an aftermarket master cylinder? If so, is there a universal spacer that fixes this, or is there something else I should be looking at? Appreciate any insight before I start throwing more parts at it.
Thanks!

Edit: the problem started with replacing just the mastercylinder. It wasn't until after that I noticed the hydro boost was leaking in the cab and believed that to be the issue. Sadly it wasn't.

Seen it a couple times, the pushrod in the hydroboost may be adjustable, pulled the master back a little and see if you can adjust the rod. Can’t remember what the clearance spec is, but 1/16 of an inch would probably be a good starting point.

I had to do this on my fox body when I put a 95 master on the 93 booster when I converted to 4 wheel disc.


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