Rear brakes do not apply enough pressure to pass inspection. With the brake applied, you can"t turn them by hand, but they do not even register on the inspection test.
I have replaced the shoes and wheel cylinders, resurfaced the drums, replaced all the fluid, fully adjusted the shoes, and bled the system several times. The problem remains. Subsequently, I replaced the master cylinder, also with no effect.
Have you ever encountered this problem, or do you have any clues to its origin?
For viewing the diagrams and step by step instructions click the link below
http://www.autozone.com/addVehicleId,1761402/initialAction,repairGuide/shopping/repairGuide.htm?pageId=0900c1528003ddb0
you can also click the options below to know more details.
Brakes
feel free for further queries.
thanks
How to flush the
brake system
1) Pull as much old fluid out ofreservoir
as possible with a turkey baster, refill with fresh fluid.
2) Fill Power Bleeder with new fluid
3) Hook Power Bleeder to master cylinder
4) Start at right rear; remove wheel
5) I built up a drain bottle which had
a "tee" in it, with a separate 1/4" or so clear plastic tubing attached
to each part of the upper "tee". Each tubing end gets attached to a bleed
screw.
6) Open both bleed screws, drain out a
1/4 pint or so (fluid looks clear with no bubbles).
7) Close bleed screws, remove tubing, reattach
wheel.
8) Go to LR, RF, LF in that succession
and repeat (4)-(7).
During (6), helps to tap brake caliper
with a rubber or wood mallet.
This will be a problem with either a collapsed brake line or the proportional valve. A collapsed line will not allow the proper flow and pressure to the brake assembly, and a faulty proportional valve will allow the pressure to bleed back into the system. You can test for these with a pressure tester. If the pressure is low but constant while the brake pedal is held down, it's a collapsed line. If the pressure drops off slowly while the brake pedal is held down, then it's the proportional valve.
It could be a metering valve or porportion valve
Have a look at bleeding procedure OF BRAKE SYSTEM. i think it helps.
There are no special bleeding procedures for the ABS SYSTEM. For bleeding, please use the standard rules as described for the conventional brake system as follows:
1.
Remove the reservoir cap and fill the brake reservoir with brake fluid.
Do not allow brake fluid remain on a painted surface. Wash it off immediately.
When bleeding by pressurized fluid, do not depress the brake pedal.
2.
Connect the vinyl tube to the wheel cylinder bleeder plug and insert the other end of tube in a half-full container of brake fluid.
3.
Slowly pump the brake pedal several times.
4.
While depressing the brake pedal fully, loosen the bleeder plug until fluid starts to run out. Then, close the bleeder screw.
5.
Repeat steps 3 and 4 until there are no more bubbles in the fluid.
6.
Tighten the bleeder plug screw.
7.
Repeat the above procedure for each wheel in the sequence shown in the illustrati'92 Jimmy rear brake failure - 895ca52.gifbr />
If that was a problem with the ABS, the brakes would just lock up (abs is anti blockage system). Instead in your case the brakes do not have enough braking power.
That simply mean that you have to do brakes calibration properly, no need for looking for complicate solutions.
If brakes are new, drive also 100 miles or so to get the brakes shape adapting and getting a stronger grip.
See also
Drum Brake Adjustment Procedure
Hi
i have a 92 chevy pu that we have a snow blade that we had the same problem.
it has Kelsey-Hayes RWAL Antilock Brakes.
The Kelsey-Hayes rear wheel antilock brake system obviously only affects the
rear brakes. On trucks with 4WD, the antilock system only works in the two-wheel
drive mode.
The conventional master brake cylinder and power booster supplies brake
pressure to the EH valve, which contains two solenoid valves: a normally open
isolation valve to block pressure from the master cylinder to the rear brakes
during antilock braking, and a normally closed dump valve for relieving pressure
in the rear brake circuits. The EH valve also contains a pressure accumulator
for storing fluid pressure during the dump or release phase of operation, and a
reset switch which allows the system to maintain proper brake pressure.
In GM applications, the brake warning light will be brightest when grounded
by the parking brake, a little dimmer when grounded by the hydraulic system and
dimmest when grounded by the ABS controller.
To determine the cause of a red brake warning light in a GM application:
brakes
we ended up picking up a used modulator control valve installed and bled ahd our problem was gone. but keep this in mind
It's important to note that one of the underlying causes of EH valve failure
is moisture-contaminated brake fluid. If the fluid is more than a couple years
old, it may contain a lot of moisture. GM trucks do not have a recommended
service interval for brake fluid, but most experts say that flushing the brake
lines every couple of years for preventative maintenance can greatly reduce the
risk of internal corrosion inside the brake lines and EH valve. But most people
totally ignore their brakes until something goes wrong. So the best you can do
is flush the system and replace the old fluid with new when the EH valve is
replaced -- then recommend a fluid change every two years to prevent a repeat
occurrence.
Air trapped in the EH valve can be another source of trouble with the RWAL
system. Some RWAL EH valves (the smaller ones) do not have a bleeder screw,
which makes the unit hard to bleed if air gets into the lines. The trick here is
to loosen the brake line connections at the valve to vent air when bleeding the
brakes.
Brakes can be bled in the usual way manually or with pressure equipment. The
wheel bleeding sequence is RR, LR, RF, LF. If a pressure bleeder is used, the
combination valve must be held open.
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There is a valve that proportions brake application 60/40 front/rear. that needs to be adjusted or replaced.... also look for contrictions in the brake lines toward the rear brakes. after the replacement of the wheel cylinders i presume the brakes were bled as well so that all air was removed. furthest wheel from the master cyclinder first.
Robert
Please click on this link to get the detailed view of the brake system:
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528003de6d
Good luck..
The conventional master brake cylinder and power booster supplies brake pressure to the EH valve, which contains two solenoid valves: a normally open isolation valve to block pressure from the master cylinder to the rear brakes during antilock braking, and a normally closed dump valve for relieving pressure in the rear brake circuits. The EH valve also contains a pressure accumulator for storing fluid pressure during the dump or release phase of operation, and a reset switch which allows the system to maintain proper brake pressure.
the brake warning light
will be brightest when grounded by the parking brake, a little
dimmer when grounded by the hydraulic system and dimmest when
grounded by the ABS controller.
To determine the cause of a red brake warning
light in a GM application:Set the parking brake. If the light gets
brighter, the problem is not the parking brake.
Unplug the connector from the combination
valve by the master cylinder. If the light remains on, the fault
is in the ABS system and further diagnosis is required.
Should not occur (replace the controller
if it does)Open isolation valve circuit or defective
ABS moduleOpen dump valve circuit or defective ABS
moduleGrounded or closed RABS or RWAL valve switch
Excessive actuations of dump valve during
ABS brakingErratic speed sensor signal
Shorted isolation valve or defective ABS
moduleShorter dump valve or defective ABS module
many more information this site ur car pro blem future use click link
http://www.automotivehelper.com/cat179-7...
better u change your rear break pad by followin step
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The antilock brake system module Give the Pressure to Each of the Wheels..
I'm sure the antilock brake module is not working properly.
have u bled the brakes
checked for leaks
checked brake booster
checked brake lines
and check the cylinders
did u machanie the drums?
'are they worn them selves?
there cant be no orther option
if you have done all that abouve they should stop you if you were doin a million mph
or just replace the hole anti lock module thats were your problem is '
chris,,,,
after 16 solutions that could have made your car a hole new braking system are you sure the guys at the shop saying not enough pressure are lying? becaus eif u tried all those soulutions it should be fixed so i suggest you take it to a machanic and see if he can diagnose the problem
×
The anti lock brake module is not functioning properly.you have get it repaired or replaced.
Need to bleed bpmv(abs unit)
When a pressure bleeder is not available, use the (two person) manual bleed procedure. One person will push on the brake pedal while the other person will open and close the bleed valves.
Important You can expect to use two quarts of brake fluid to thoroughly bleed the system.
1.
Begin by opening the internal bleed screws 1/4 to 1/2 turn, on each side of the BPMV (Figure 2).
2.
Attach the valve pressure bleeding tool J 39177 to the left and right high pressure accumulator bleed valve stems of the BPMV (Figure 3). Tighten tool J 39177 only finger tight.
Note: It is not necessary to attach bleeding tool J 39177 to the combination valve when using the manual bleed procedure.
3.
Bleed each wheel in the following sequence:
^
Right rear
^
Left rear
^
Right front
^
Left front
Note: Rear wheel bleeder valves are 5/16 in. (8 mm) and front wheel bleeder valves are 10 mm.
Note: A clear plastic hose can be attached to the bleeder valve and immersed into a container partially filled with clean brake fluid.
4.
Slowly apply the brake pedal one time and hold.
5.
Loosen the bleeder valve to purge the air from the wheel cylinder/caliper.
6.
Tighten the bleeder valve and slowly release the pedal.
7.
Wait 15 seconds.
8.
Be sure to check the master cylinder fluid level after 4-5 strokes to avoid running dry.
9.
Repeat steps 4 through 8, until all air is purged from the wheel cylinder/caliper.
Note: It may be necessary to repeat this sequence as many as 15 to 20 times per wheel.
10.
Fill the master cylinder to the proper level and replace lid.
11.
CLOSE and tighten the two BPMV internal bleed screws (Figure 2) to 7 N-m (60 lbs.in.).
12.
Remove the valve pressure bleeding tools J 39177 from the BPMV high pressure accumulator bleed valve stems and the combination valve.
13.
With the ignition switch "ON" and the engine off, bleed the pump and pressure (lower) portion of the BPMV by performing six ABS function tests with the Tech-1.
Important DURING THE TECH-1 FUNCTION TESTS, THE BRAKE PEDAL MUST BE FIRMLY DEPRESSED. THIS WILL PUSH ANY AIR FROM THE CONTROL AREA OF THE BPMV INTO THE BRAKE SYSTEM.
14.
Finally, rebleed the four wheel cylinder/calipers again, to purge any remaining air put into the system during the function tests. Use either the pressure bleed or manual bleed for this step.
Important DO NOT OPEN THE BPMV INTERNAL BLEED SCREWS OR DEPRESS THE HIGH PRESSURE ACCUMULATOR BLEED VALVES WHEN REBLEEDING AFTER THE FUNCTION TESTS.
15.
Tighten all four wheel cylinder/caliper bleeder valves to 7 N-m (60 lbs. in.).
16.
Fill the master cylinder to the proper level with brake fluid.
17.
Apply firm pressure to the brake pedal and evaluate the brake pedal feel.
Important MAKE SURE YOU HAVE A GOOD, HARD BRAKE PEDAL BEFORE ATTEMPTING TO MOVE THE VEHICLE.
18.
Repeat the entire brake bleed procedure if necessary
Hi....
In your problem with the rear brakes.
If you have replaced the Rear brakes,cylinders and master cylinder.
If your car DON'T pass the inspection.
Is mean you have a problem of Brake Fluid Pressure..
But On my PC. I saw your vehicle is Equipaded with ABS. " anti lock Brake system".
The antilock brake system module Give the Pressure to Each of the Wheels..
I'm sure the antilock brake module is not working propertly.
Or you have Air Traped in the System.
Try bleeding the system Including the ABS module.....
If you Don't feel any diference.
Replace the ABS module. New is spensive But you can get from a Junk yard.
OK.... I hope this help to try diagnostic your problem.
Thank you for use fixya...
As I told you before.
I recomend Replace the ABS UNIT.
If you have checked the Speed sensors. and are good.
You have replaced everything, But not the ABS UNIT.
The PRESSURE SELENOIDS VALVE. are stuck or locked up.
and make a restriction to the outlet ports.
Check the condition of the Brake lines.
Open the port from the abs unit. check if there a Pressure. Open the line on the cylinder end.
Aply compressed air from one end to the other. If the air not pass replace the Brake line.
If pass do the same with the other LIne. the Brake lines
some times are damaged , due at corrotions, bent for piece left on the rod, crached.
I'm a MECHANIC and have ben this problem on the same kind of vehicle.
Is the job I do everyday.
×
Hi,
May I offer an alternate possibility, since you have checked most if not all of the brake system, could it be that your vehicle has a Brake Proportional Valve (aftermarket). Its function is to distribute braking force based on a certain ratio.
Additionally, you may want to try redoing everything. Except after draining the brake fluid from the system and removing the slaves, apply compressed air at the master's end of the rear brake lines and the opposite (from the rear slave line). You may want to consider that leftover fluid would spray out of the free ends and therefore preventive measure should be included.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
Good luck and kind regards. Thank you for using FixYa.
The repartision valve follow the brake line from the back to the valve check the condition of the line at the same time and rubber hose in the back ok at the valve remove the line check the pressure coming out of the valve if all the line rubber and steel good drill the valve to put the hole thats in the valvejust a bit bigger you gonna see the differense night and day try it out pierre
So here we start off with some basic tips to repair your brakes.
Visual Inspection
The initial stage requires a visual inspection. A visual inspection takes a few minutes and is done every time the oil change takes place. One can start with checking the color of the fluid in the master cylinder. The change in the color of the oil can help in identifying the impending problems. A transparent and almost clear fluid is good news. But if the color of the fluid turns brown, this means it has expired and is not suitable for the vehicle.
Further Inspection And Cleaning
Brake pads are an integral element of the braking system in a car. As you use your brakes in everyday driving, you will slowly wear down, and, eventually, need to replace the brake pads.
Disc brakes have been used on the front wheels of cars for decades now - some models are even equipped with disc brakes on all four wheels. You will still find some cars being made with disc brakes at the front and drum brakes on the rear wheels. The reason for this is that the front wheels carry the biggest portion of the load under braking conditions, and disk brakes are more effective.
Since the front wheels, and thereby the disc brakes, carry the biggest portion of the load under braking conditions, it is critical that your front brakes are operating as well as possible. When it comes to your car's brakes, there is simply no room for substandard or worn out parts.
Older cars that had disc brakes on the front were equipped with what was referred to as a 'squeaker bar' on the brake pad. This piece of metal would make an extremely loud squeaking noise once the brake pads were worn down. This was how you knew that it was time to replace your worn-out pads. Cars today come with an electronic sensor on the brake pad. When your brakes have worn down, you will see a warning light on your dashboard.
When this dashboard light is illuminated, or when you start hearing a squeak upon brake application, it is time for you to have your brake pads replaced. If you wait to do so, you are not only causing damage to the brake as a whole, but you are taking a big safety risk.
If your caris equipped with a wear sensor in the brake pads, you will want to have this sensor replaced along with the pads. The sensor is not generally included with the new pads. If you wait for your brake pads to wear down completely, they will begin to damage your disc rotor - the replacement of which is costly.
When you press your brake pedal down, the pistons on your brake caliper will push the brake pad down against the brake disc. Ultimately, the pads pressing against the disc is what slows and stops your car. As you can imagine, this process will result in the deterioration of your pads. This is how brake pads are supposed to work; they are not intended to last the life of your car.
Brake pads are made from a variety of materials. You can purchase pads made from longer-lasting materials if you wish. Those of higher quality also help your car to stop more quickly under heavy braking conditions. Choosing the highest quality brake parts is a smart decision for your safety. Even if you own a Chrysler, you can use aftermarket brakes that will outperform the factory Chrysler parts. Chrysler parts work fine for most drivers, but performance enthusiasts and those who want extra stopping power, will often opt for aftermarket brake parts.
Be sure to use a great deal of care when replacing your brake parts. If you do not feel comfortable with your own mechanical skills, it may be best to have a professional install the new parts for you. Working on your own brakes is not the time to test your mechanical aptitude. If your brakes are installed incorrectly, they may fail and cause a severe accident.
It is recommended that you have your brakes checked each time your vehicle's oil is changed - about every 6,000 miles. This quick inspection, paired with proper maintenance of your brake pads, will prevent problems down the road, ensuring the safety of you and your family.
Have you checked the vacuum source of the master cylinder?. if it has a leak then it wont work properly. check the hose from cracks and chippings. check where it is connected and check if you have a good source of vacuum from your engine
is the pedal hard to step unto?
you have replaced everything and that is the only part that you have not look unto yet.
i hope i was able to fix ur problem..
tnx
drcool
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Usually answered in minutes!
Vacuum hose is good; no leaks. Vacuum at booster is 21 inches. Pedal travel is normal. Front brakes work fine.
Your answer gives sage advice, but unfortunatly it does not address my problem. As I originally wrote, the rear brakes were completely re-done. The emergency brake works fine. It is the lack of sufficient pressure in the hydraulic system that is the problem.
I need the advise of someone with expertise in ABS systems to tell me if any of those components could be the cause of insufficient pressure in the rear hydraulic lines, and if so, which component is the most likely suspect. There are no diagnostic codes present. Rear wheel sensors both have correct resistance readings. Problem persists even when the electrohydraulic control unit is electrically disconnected.
I need the advice of someone with expertise in the ABS sustem for this vehicle. I need to know if any of those components can cause reduced pressure in the rear brake lines, and if so which component is the most likely suspect. There are no diagnostic codes present. Resistance readings on both rear wheel sensors are whithin range. The problem persists even when the electro-hydraulic control unit is electrically disconnected.
The ABS warning light is not on.
There is no dump valve on this model. That function may be built into the EHCU.
NEW MASTER CYLINDER HAS BEEN APPLIED AND THE SENSOR DOES NOT REGISTER THAT THE ISSUE HAS BEEN FIXED
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