Check the brake fluid first.is it low or no brake fluid at all.is the brake fluid got dried up or leaked out.
Sounds like the power brake booster is bad, that is what the master cylinder is bolted too. There is a rubber hose that has a plastic valve in it were it snaps into the booster, Pull that rubber hose out of the booster and off of the engine, Now the end that you took off the engine. You should be able to **** through the line, but not be able to blow through it. If you can then replace the valve, It is a one way valve.
If that is all right then hook hose back up to the engine and start engine, You should hear a major vacuum leak at the valve end, put you finger over the valve and it should stop making noise and engine should smooth out. If it don't the rubber hose must be leaking or the tube on the engine were the hose hooks to is stoped up.
Also check the master cylinder if power booster is replaced.
If the brake light is coming and going check the brake light switch.
check fig for the internal assembly parts:--
To check engine vacuum, connect a vacuum gauge to the supply hose that runs from the intake manifold to the booster. A low reading (below 16 inches) may indicate a hose leak or obstruction, a blockage in the exhaust system (plugged catalytic converter, crushed pipe, bad muffler, etc.), or a problem in the engine itself (manifold vacuum leak, bad valve, head gasket, etc.).
The condition of the diaphragm inside the booster is also important. If cracked, ruptured or leaking, it won't hold vacuum and can't provide much power assist. Leaks in the master cylinder can allow brake fluid to be siphoned into the booster, accelerating the demise of the diaphragm. So if there's brake fluid inside the vacuum hose, it's a good indication the master cylinder is leaking and needs to be rebuilt or replaced. Wetness around the back of the master cylinder would be another clue to this kind of problem.
To check the vacuum booster, pump the brake pedal with the engine off until you've bled off all the vacuum from the unit. Then hold the pedal down and start the engine. You should feel the pedal depress slightly as engine vacuum enters the booster and pulls on the diaphragm. No change? Then check the vacuum hose connection and engine vacuum. If okay, the problem is in the booster and the booster needs to be replaced.
Vacuum boosters also have an external one-way check valve at the hose inlet that closes when the engine is either shut off or stalls. This traps vacuum inside the booster so it can still provide one or two power assisted stops until the engine is restarted. The valve also helps maintain vacuum when intake vacuum is low (when the engine is under load or is running at wide open throttle). You can check the valve by removing it and trying to blow through it from both sides. It should pass air from the rear but not from the front.
Replacing a vacuum booster is a fairly straight forward job. All you have to do is disconnect it from the brake pedal on the inside and unbolt the master cylinder. The pushrod that runs from the booster into the back of the master cylinder must have the specified amount of play.
You will typically find the power brake booster mounted on the firewall attached to the master cylinder. The master cylinder is connected to the brake pedal.
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It would be helpful to know if it is only the red brake lamp or
both the yellow and red. Here are some more items to check from Service Manual:
Brake Warning Indicator always ON
- Low brake fluid level: Add fluid, check for leaks and bleed system as required.
- Ignition wiring routed too closely to fluid level indicator assembly:
Reroute wiring as required.
- Damaged float assembly: service or replace as required.
- Shorted light circuit: correcte short in warning circuit.
- Worn or damaged brake fluid level indicator: replace brake master cylinder reservoir.
- Leak in brake system: service leak
- Parking brake engaged: release parking brake.
Solve? If not, go to Pinpoint Test B...
PINPOINT TEST B: BRAKE WARNING INDICATOR ALWAYS ON
B1 CHECK PROPER FUNCTION OF BRAKE WARNING INDICATOR WHEN RELEASED
Key on or in ACCY.
Verify parking brake is fully released.
Is the red brake warning indicator on?
Yes: GO to B2
No: Brake warning indicator bulb and circuits are functioning properly.
B2 CHECK BRAKE FLUID LEVEL IN BRAKE MASTER CYLINDER
Check the brake fluid level at the brake master cylinder reservoir.
Is the brake fluid level within specification?
Yes: GO to B3
No: CHECK for leaks in the vehicle brake system and SERVICE as required. FILL the brake master cylinder reservoir to the required level. REPEAT B1 .
B3 VERIFY FLOAT BUOYANCY
Remove the brake master cylinder filler cap from the brake master cylinder reservoir.
Using a clean steel implement, attempt to push the float down.
Does the float move down?
Yes: GO to B4
No: REPLACE the brake master cylinder reservoir. BLEED the brake system. REPEAT B1 .
B4 CHECK REAR ANTI-LOCK BRAKE SYSTEM (RABS) MODULE
Key off.
Disconnect RABS module harness connector.
Key on.
Does the brake warning indicator turn on?
Yes: RECONNECT RABS module connector. GO to B5
No: REPLACE anti-lock brake control module. RECONNECT RABS module connector. REPEAT B1 .
B5 LOCATE CAUSE OF RED BRAKE WARNING INDICATOR ON
Key off.
Disconnect the fluid level switch harness connector from the brake master cylinder reservoir.
Key on.
Does the brake warning indicator turn on?
Yes: Diesel only: GO to B6 . All others: GO to B7
No: GO to B8
B6 LOW VACUUM SWITCH CHECK (DIESEL ONLY)
Key off.
Disconnect low vacuum switch harness connector.
Key on.
Does the brake warning indicator turn on?
Yes: GO to B7.
No: RECONNECT all loose connections. REFER to Section 06-07B to diagnose reason for low vacuum switch actuating the brake warning indicator.
B7 PARKING BRAKE SWITCH CHECK
Key off.
Disconnect parking brake switch harness connector.
Key on.
Does the brake warning indicator turn on?
Yes: LOCATE and SERVICE short to ground in Circuit 977 (P/W), 640 (R/Y), 531 (DG/Y), or 162. RECONNECT all loose connections. REPEAT B1.
No: REPLACE parking brake switch. RECONNECT all loose connections. REPEAT B1 .
B8 BRAKE WARNING INDICATOR TEST
NOTE: The brake warning indicator should only light when the ignition switch is in the START position or when the ignition switch is on and the parking brake is applied (gasoline), or when the vacuum is low (diesel).
Release parking brake. Check brake fluid level in brake master cylinder reservoir. Fill as required.
Key in ACCY or on.
Does brake warning indicator turn on?
Yes: CHECK switch wiring for possible short to ground. SERVICE or REPLACE as required.
No: GO to B9 . GO to B10 .
B9 MASTER CYLINDER FLUID LEVEL SWITCH WIRING CHECK
Partially drain the brake master cylinder reservoir.
Key to RUN and observe brake warning indicator.
Does the brake warning indicator illuminate?
Yes: FILL brake master cylinder reservoir. Switch OK. CHECK for open in fluid level switch to brake warning indicator wiring.
No: SERVICE as required. If no open found, GO to B10 .
B10 MASTER CYLINDER LEVEL SWITCH CHECK
Manually push the float in the brake master cylinder reservoir to the bottom.
Key to RUN and observe the brake warning indicator.
Does the brake warning indicator illuminate?
Yes: REFILL brake master cylinder reservoir. Switch OK.
No: GO to B11 .
B11 FLUID LEVEL SWITCH CHECK
Key off.
With the fluid level switch harness connector disconnected, jumper between Circuits 512 (T/LG) and 531 (DG/Y).
Key on.
Does the brake warning indicator turn on?
Yes: Locate and Sercive short to ground in Circuit 512 (T/LG). Reconnect all loose connections. Repeat B1.
No: Replace brake master cylinder reservoir. Bleed brake system. Reconnect all loose connections. Repeat B1.
This is the only TSB... the only thing of interest is the possibility of crossed lines.
TSB 07-11-10 06/11/07
BRAKE PEDAL KICKBACK OR GRABBING
FORD:
1997-2007 E-Series
1999-2008 F-Super Duty
2000-2005 Excursion
This article supersedes TSB 99-25-8 to update the vehicle model years.
ISSUE
Some 1999-2008 F-Super Duty, 2000-2005 Excursion, and 1997-2007 E-Series vehicles equipped with Hyrdo-Boost(R) brake booster system may exhibit a brake pedal kickback and/or grabbing condition when applying the brakes. This may be caused by contamination within the power steering system.
ACTION
Filter the power steering fluid by installing a temporary filter in the power steering system. Refer to the Service Procedure below.
SERVICE PROCEDURE
1. Verify that the line from the pump and the line to the gear at the Hydro-Boost(R) are in their correct orientation (and not crossed). The passenger side goes to the pump, the driver side goes to the gear.
2. Attach a pinch-off clamp to the lower power steering hose approximately 6" (15 cm) from the lower port of the power steering cooler to keep fluid from emptying out of the system when the hose is disconnected.
3. Disconnect the power steering hose from the lower port on the cooler. Cap the cooler port to minimize fluid leakage and immediately install the temporary filter in line with the power steering hose using hose clamps to retain the filter (the filter needs to go in the low pressure line that goes from gear to cooler to reservoir, where it would be most accessible).
4. Attach the other end of the filter to the cooler using the clamps provided.
5. Remove the pinch-off clamp from the power steering hose.
FILTERING PROCEDURE
CAUTION BE SURE THAT THE PARKING BRAKE IS APPLIED DURING THE FOLLOWING STEPS 1-7.
1. Check power steering fluid level before starting the vehicle.
2. Start the vehicle and allow it to idle for approximately 15 seconds.
NOTE DO NOT HOLD THE STEERING AT LOCK FOR MORE THAN 5 SECONDS.
3. Turn steering wheel lock-to-lock 10 times.
4. Pump service brake pedal hard to floor 25 times.
5. Turn steering wheel lock-to-lock 5 times.
6. Remove the filter and reconnect the power steering line to the cooler. Discard the filter. Fill the power steering system. Refer to Workshop Manual (WSM), Section 211-00 Power Steering System Filling.
7. With the engine at idle, gradually apply the brake pedal until fully applied. If the brake pedal kickback persists, replace the Hydro-Boost(R) brake booster. Refer to WSM, Section 206-07.
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One more thing with the assistance of " baddad1 " you may have a bad
vacuum pump. Low vacuum will turn the red brake lamp on and make
the pedal feel hard to push.
go back up to the top... i gave you the readers digest condensed version
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Try bleeding all the calipers and wheels cylinders first. Start with the furthest one from the master cylinder and work your way up to the closest one. If the problem is unchanged... Replace the Master Cylinder for one or two internal seals are leaking causing this. If the master cylinder has an internal leak it will not be detected until you have a problem such as the one your having now
If the master cylinder is leaking internally, why does the petal stay hard?
Start the engine and let it run for one minute. Shut it off with your foot firmly on the brake pedal. If the brake pedal slowly goes down after shutting the car off within 30 seconds it has a vacuum leak within the booster or a vacuum hose
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If the brake light is on, this tells me that the level could be lower than normal. If the brake level switch is bad, replace. But, I think that you need to check that level.
If the brakes are hard, but not very effective, there could be a problem with the master cylinder end of things.
Have your ABS checked out as well, even if there is no light.
Hope this helps.
I was taught that if you disconnected the booster tube to the booster at the check valve, after turning the car off, there should be so much residual vacuum that when you take it off, you should hear a loud rush of air indicating proper vacuum.
The vacuum gauge can be used to test if there is enough vacuum as well, as measured in inches of Hg or mercury, but I like the 'swoosh' method better. That tells you if the booster is holding vacuum.
Good luck on analyzing the booster function.
Booster holds vacuum for several hours after engine is off, but not overnight. Still need to know if 6 in. vacuum is enough to asist brakes. Also need to know if typical vacuum pump failure is gradual, partial or complete and rapid.
you need 17 inches of vacuum to make the brakes work well (not 6 in.).
This could be your problem.
Usually, the brake booster fails gradually, not holding vacuum in it diaphragm through a pin
***** hole or leak at a seam.
It can fail quickly if in an accident that disturbs the booster, but most booster's I've seen either hold vacuum or don't and can very quickly be diagnosed by an experienced technician or mechanic who is used to hearing that loud 'swoosh' of air, when pulling the check valve and tube out of the booster, shortly after shutting the engine off.
I hope this helps.
Based on your comments, I would be confident to say that your booster needs to be replaced to hold vacuum overnight and to hold it at a higher vacuum than only 6 inches.
So, I wish you luck in fixing this problem. It's actually not too hard to change the booster.
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Check the brake fluid level and, the brake pads / shoes thickness / and,condition then drive the truck slowly do not press the brake pedal stop using the parking brake only. if the truck stops easily: check for binding at the master cylinder push rod or, calipers if they are good; replace the master cylinder if the truck stopped easily replace the brake balancing valve
Fig. Fig. 1: Vacuum booster mounting
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This is a diesel. Vacuum is generated by vacuum pump powered by engine's serpentine belt. This appears to be working. Booster holds vacuum.
brakes work, pedal is hard, e-brake will stop truck. Checked vacuum at booster hose, reads 6 in. at idle. Revved motor and it went up to 9 in. but slowly went back down to 6 in. Is this normal? If not what should it be?
I may need to clarify the brake light issue. It has been coming on off for quite some time before brake function began to deteriorate. It does not seem to corelate with function issue. I am more interested at this point in finding out how to test the booster and vacuum pump function. Specifically, how many inches of vacuum should i have at the booster? And is there a way of testing the booster short of replacing it?
Master cylinder holds pressure. No detected leaks or use of fluid. All four brakes feel to be working evenly.
i have a 1997 fsuper duty to witch i changed the hydro booster and now i can not take it of park
sounds like ineffective vacuum supply. pump should do the work of a well tuned engine since thats what its taking the place of. engine manifold vacuum is normally 15-18in. hg. verify the belt is intact and being driven correctly. inspect all the vacuum supply parts in the system. if no cause is found you will need to try another pump. take your old one off first so you can see all about it, turn it, etc. looking for external causes like loose clamp or rotted or damaged hose
vacuum volume is just as important as a reading, unfortunately, there is no simple device. a manometer is a large tube, clear, that moves an object within to depict vacuum in (in. h2o) you may have seen a small version at the doctors office on the wall. at any rate. you not only need some vacuum but alot of repetitious replenishing of volume of vacuum. thats why they suspended such a large plate and diaphragm in the pic below. an 8 cyl engine constantly replenishes the volume while its running. when shut off, you lose it quick by stepping on the brake a few times. replace the pump
oh, yea, the reason for the large plate and diaphragm is they can use smaller and lighter calipers and piston bore sizes without affecting the driver's perception of his stopping power. the truck weighs less, so it can obey CAFE rgulations about fuel economy, plus other advantages
when you lose the pull on the suspended diaphragm, you now feel the actual force a master cyl. exerts. and, the resulting force applied by the hydraulic actuation of the caliper pistons it has...hard as a rock pedal, man.
ineffective coefficient of friction because the pads just aint feelin it.
also, the light is coming on because the assist amount is weak. wait for the pump to catch up without braking...and it goes out...see if i'm right
if its still on after repair and i'm wrong? hydraulic concern with a leak has to be there also because the light responds on most systems to brake imbalance between hydraulic circuits.
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