2001 Ford Ranger pedal to floor only when truck engine running

WESLEYMAC

MEMBER
2001 FORD RANGER
6 CYL
2WD
AUTOMATIC
145 MILES

I replaced the front calipers and the master clylinder on my Ranger. The brakes had failed. I bled the rear brakes and went rr-rl-fr-fl and bled each brake 4 times. I still get a loose pedal to the floor when the engine is running. I bled the master clylinder. How I did a booster brake test by turning off the truck, pumping the brakes half a dozen times and then turning on the truck engine. The pedal doesnt "drop" a little then slowly rise a lil. It just goes down to the floor when pressed. The Brakes do engage but very little.
Everything I read says that the pedal should feel hard when braked if the vacuum booster is bad.
How do I check the brake booster and its vacuum line? Are there any special tools needed or procedures to change a brake booster - out to re-vacuumize the line to the master?

3 Replies

MERLIN2021

MECHANIC
17,250 POSTS

HYDRAULIC CONTROL UNIT (HCU) 1. Clean dirt from around master cylinder reservoir cap. Fill master cylinder reservoir with clean DOT 3 brake fluid. Connect drain hose to right rear bleeder screw. Submerge other end of hose in clear container full of clean brake fluid. 2. Pump brake pedal, and then hold firm pressure on brake pedal. Loosen right rear bleeder screw until fluid flows from screw. Have an assistant maintain pressure on brake pedal while tightening bleeder screw. Repeat bleeding procedure until brake fluid flow is clear and free of bubbles. Refill master cylinder reservoir as necessary. 3. Tighten right rear bleeder screw and remove drain hose. Proceed to left rear, right front and left front wheels in sequence. Install New Generation Star (NGS) tester with Cable (007-00531) to Data Link Connector (DLC) located behind left side of instrument panel, and follow NGS tester instructions. Repeat bleeding procedure for all 4 wheels.
VACUUM POWER BOOSTER 1. With a "T" fitting, connect vacuum gauge into vacuum line between engine and power brake booster. With engine at operating temperature, gauge should read 15-19 in. Hg vacuum at idle with transmission in Neutral. If reading is less than specification, stop engine, disconnect vacuum hose at power brake booster and cap open end of hose and open port of vacuum "T". 2. Start engine, and allow it to idle. If reading is still less than 15-19 in. Hg vacuum, engine is producing low vacuum and mechanical problem must be corrected. If vacuum is to specification, check plastic check valve, rubber grommet and vacuum hose connection at power brake booster. 3. With low engine vacuum corrected and/or leaking components replaced, start engine, and allow it to idle. Stop engine, and depress brake pedal for a few seconds. If vacuum drops to zero, booster is leaking and requires replacement. Page 1 of 1 DISC & DRUM -2001 Ford Ranger 4/20/2009

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Monday, April 20th, 2009 AT 10:28 AM

WESLEYMAC

MEMBER
1 POST

Thank you guys. I did all that and the check valve was fouled(on the booster) with the old stuff from inside the vacuum line hose from the top of the engine. I cleaned it up with brake cleaner spray and put it back in and the booster then had enough vacuum. Also in re bleeding the lines and calipers I found a tiny leak sucking air into the sytem in left rear brake clylinder.(I also adjusted the brake pedal connection at the booster under the dash>
I used brake cleaner once again to id that and put a new brake clylinder on. I am going to go to the dealer tommorw and get a new vacuum lione hose to install.
Your advice helped me to stay organized about this project and gave me the insight I needed to diagnois
the real problem!

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Monday, April 20th, 2009 AT 11:40 PM

MERLIN2021