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brakes won't work with new master cylinder

Old 06-13-2018
Thread Starter
Join Date: Jun 2018
Location: Lancing
Posts: 4
brakes won't work with new master cylinder

Hello there, i'm new here and that's because a few days ago i bought my very first Ford ever, disguised as a Mazda B4000 of course. Anyway the important issue is this. I knew the master cylinder was going out on the way home and it wasn't so bad yet brakes are something to take seriously so i changed it. Now even with the new one in there and after bench bleeding it (should've done that first), and bleeding the brakes literally 4 times, i'm still not getting enough pressure to stop this thing from rolling. I have heard mention of the brake booster possibly being bad and plan on getting a new one. Is there anything anyone can suggest to me? I need real help from people who know these trucks much better than i do.

Its a 2004 Mazda B4000, 5 speed, 4.0, 4x4 with 10 inch drums. Thank you.
Old 06-13-2018
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Join Date: Jan 2014
Location: Vancouver, BC
Posts: 13,047
Welcome to the forum

When you did the 4 wheel bleed were you getting good flow from each bleeder?

Engine off, press brake pedal down 3 or 4 times, should be very hard to press it down after 2nd or 3rd time, very hard.
Start engine, press down on pedal, should now be easy to press down, with Vacuum power assist from booster.
If it is easy then booster is OK

You will have 4-wheel ABS on 2004, could be a module problem
Does the ABS light on the dash work?
Should come on with Key ON, then go off, thats a Bulb test only not a system test
Previous owner make have pulled the bulb, hiding ABS issue so he could sell it

With pickup trucks 70% of braking is done with front wheels, so if front brakes have an issue then it feels like there are almost no brakes
If you have 2 brake lines coming out of the Master Cylinder then 70/30 proportioning valve is in the Master
If 1 brake line then there is an external proportioning valve, 1 line in and 2 lines out
Proportioning valve sends 70% of pressure to front brakes and 30% to rear, cars use 60/40 proportioning valves

Last edited by RonD; 06-13-2018 at 10:53 AM.
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