Brake fade problem at idle speed
 

When I am in my driveway and in drive going forward slowly the brake pedal travels veryslowly towards the floor. When I release my foot and repress the brake it seems normal and the travel to the floor is gone. When I drive at normal speeds it happens that if it hit the brake 3 times I have to take my foot off the brake and repress it in order to have a strong brake. I though it was the master cylinder but if it was it would go tothe floor all the time. I also thought it was a vacum problem but there are no leaks and the idle seems fine when I have my foot on the brake in drive.

RE: Brake fade problem at idle
 

does sound like master cyl. to me, hows the linings?

RE: Brake fade problem at idle
 

If it was the master cylinder wouldn’t Iloose pressure all the time rather then at a forward idle with light light pressure in the brake pedal. Remember it only goes to the floor on constant light pressure on the pedal and ifI release my foot and reapply the brake it's fine and strong with plenty of pressure.I went to a local machanic when I told him what is was doing he said let me guess 01 02 03 town and county I said yes he then said he had a car last week and they changed the master cyclinder and it was nto that then they changed the abs modual with the abs pump and tha fix it.
I order a used master cyclinder and abs pump that has the modual attached is there a special way to bleed the abs system I heard it has to be taken to the dealer.

RE: Brake fade problem at idle
 

WellI was right it was the ABS module the brakes are great I got a use one for 35.00 and a used master clyinder total 90.00 inc shipping.
New the part was 700.00 at dealer master clyinder 107.00 tow to garage 60.00 pressure becasue they say you have to at the dealerer (bullcrap) 60.00 brake fluid 7.00. Total 807.00 My total cost doing it my self 90.00. No special bleeding needed did it my self and the wife.
Nice being an Xmachanic even without chrysler experience.

RE: Brake fade problem at idle
 

Well 1 month later and it's back again after a I changed the abs pump and master cylinder ow what bleed again?

RE: Brake fade problem at idle
 

maybe you do need a special bleeding proces.
find which type of ABS pump do you have, we'll come up with the technique.

make a test:
-how does brake pedal feel first time you push it?
don't press it slightly, or in moving. just start the engine and after few seconds, press the pedal and feel what it's like. is it any different than if you press 2 or 3 times after that?

if your brake pedal is going down to the floor by applying light pressure, i suspect oil seals in front calipers and dirt that prevents movement of the brake pistons. don't ask me why it happens, but I saw simmilar problem once.
new oil seals and cleaning of brake calipers solved the problem.

RE: Brake fade problem at idle
 

The first time and all times I press it it seems fine it is only when I put very slight pressure on the brake in drive at idle going foward. If I stand still in park or drive and apply pressure it's ok.
I can olny make it happen going forward or in reverse at idle speed no gas and light light light pressure on the brake pedal. I take my foot off the brake reapplyi t and the brakes are great.
I will say though it feel like there it no power assit untilIpump it 2-3 times, it feel like a pre 70s brake system with 4 drum brakes.I will rebleed the brake this morning and see what happens.

RE: Brake fade problem at idle speed
 

Ok I bled the brakes no help. I dont understand why htis is back after it seemed fixed for a month and 2 weeks. I replaced the abs pump and the master cylinder and bled the brakes adnit was fine. I am thinking about pay the dealer for a power bleed what do you think out there?

RE: Brake fade problem at idle speed
 

I still don't know what kind of engine you have.
bear in mind that gasoline engines develop very small vacuum on idle, becouse of weak air flow (poor brake assistance on idle). I suppose that this kind of behaviour of brakes is not normal on your type of car and that some machanic tested this.


you already had the ABS pump down.
find it's type and tell me. I'll tell you if you need special tehnique for bleeding the pump.

so far, it looks like there is no air in the brakes, so any aditional bleeding of the brakes is not necesarry. though, ABS pump has valves and very small pipes and some air may still be trapped there.

as you changed almost everything else, I'm still conviced that cleaning the calipers and brake pistons will solve the problem.

RE: Brake fade problem at idle speed
 

heres what we use for bleeding abs.silly question does this have a check valve on the booster from intake manifold? moe
STANDARD PROCEDURE - ANTILOCK BRAKE SYSTEM BLEEDING
The base brake's hydraulic system must be bled anytime air enters the hydraulic system. The ABS though, particularly the ICU (HCU), should only be bled when the HCU is replaced or removed from the vehicle. The ABS must always be bled anytime it is suspected that the HCU has ingested air. Under most circumstances that require the bleeding of the brakes hydraulic system, only the base brake hydraulic system needs to be bled.
It is important to note that excessive air in the brake system will cause a soft or spongy feeling brake pedal.
During the brake bleeding procedure, be sure the brake fluid level remains close to the FULL level in the master cylinder fluid reservoir. Check the fluid level periodically during the bleeding procedure and add DOT 3 brake fluid as required.
The ABS must be bled as two independent braking systems. The non-ABS portion of the brake system with ABS is to be bled the same as any non-ABS system.
The ABS portion of the brake system must be bled separately. Use the following procedure to properly bleed the brake hydraulic system including the ABS.
BLEEDING
When bleeding the ABS system, the following bleeding sequence must be followed to insure complete and adequate bleeding.
[ol][*]Make sure all hydraulic fluid lines are installed and properly torqued.[*]Connect the DRBIII® scan tool to the diagnostics connector. The diagnostic connector is located under the lower steering column cover to the left of the steering column.[*]Using the DRB, check to make sure the CAB does not have any fault codes stored. If it does, clear them using the DRB.
WARNING: WHEN BLEEDING THE BRAKE SYSTEM WEAR SAFETY GLASSES. A CLEAR BLEED TUBE MUST BE ATTACHED TO THE BLEEDER SCREWS AND SUBMERGED IN A CLEAR CONTAINER FILLED PART WAY WITH CLEAN BRAKE FLUID. DIRECT THE FLOW OF BRAKE FLUID AWAY FROM YOURSELF AND THE PAINTED SURFACES OF THE VEHICLE. BRAKE FLUID AT HIGH PRESSURE MAY COME OUT OF THE BLEEDER SCREWS WHEN OPENED. [*]Bleed the base brake system using the standard pressure or manual bleeding procedure. (Refer to 5 - BRAKES - BASE - STANDARD PROCEDURE)[*]Using the DRB, select ANTILOCK BRAKES, followed by MISCELLANEOUS, then BLEED BRAKES. Follow the instructions displayed. When the scan tool displays TEST COMPLETED, disconnect the scan tool and proceed.[*]Bleed the base brake system a second time. Check brake fluid level in the reservoir periodically to prevent emptying, causing air to enter the hydraulic system.[*]Fill the master cylinder reservoir to the full level.[*]Test drive the vehicle to be sure the brakes are operating correctly and that the brake pedal does not feel spongy.[/ol]