2nd Gen Non-Engine/Transmission Soft Brake Pedal/Brake Master Cylinder

[MAYoung]

1998. 5 Dodge 2500 Quad Cab 4x4 5-Speed NV4500 Manual Transmission Stock Tires/Wheels



Gentlemen:



I have reviewed numerous posts on this issue but I remained confused as to trouble shooting the problem.



I replaced the front disc brake pads on my truck this weekend. My problem remains that I have a soft brake pedal even through I have bled the brake system 3 times.



Based on other posts, I see that I failed to let off the bleed screw on each of the front calipers when I pushed back the pistons. The excess fluid did return to the master cylinder which I removed via a turkey baster. The fluid was discolored to a brown/rust color even though the system was flushed when I did the rear brakes in March of this year.



My question is this: How do I determine if I damaged the brake master cylinder? Other posts suggest that if the pedal continues to the floor with moderate brake pedal pressure (but the brakes are working), you have a master cylinder problems.



I am not getting any air from the bleed screws at the 4 wheels. The fluid is now clear. I do not have 4 wheel ABS, only rear wheel antilock brakes (RWAL). I bleed the system by having a helper press on the brake pedal as I let off the bled screw into a bottle and then retightening the screw before the pedal is released.



The brakes work well now but the pedal is soft. I cannot really evaluate the total system with the softness of the brake pedal.



Suggestions for further trouble shooting? Am I jumping to the conclusion that it is the M/C?



Thank you in advance,



Mark Young

 

[SFPADGETT]

Replacing the master cylinder this morning on one of our trucks--soft pedal, pedal falls to floor at stop lights--scary feeling.

 

[Mhannink]

get a hand operated vac pump and some clear hose. i just did lines a calipers on my brakes along with everything else and it took me a very long time to bleed the system. i thought id had it done but still had soft brakes. so i put a vac pump attached to a container opened the system drew a vacuum on it and started pumping. after i pump about 4qts through both sides combined i had amazing brakes maybe better then a 3g. all im saying is make really good and sure its not just air.



by the way while i was doing all this i found more air pockets in the system i didnt think could be there as well as a lot of little bubbles those bubbles all add up when they are compressing

 

[MAYoung]

Thank you for the quick responses. I am going to bleed the system one more time and then go for a test drive. I will try and sort out any improvement or changes.



An earlier post suggest that you have a M/C problem when the brakes fundamentally work put the pedal continues to go to the floor with light to moderate pedal pressure. I will be checking for that. If not, more bleeding of the system.



M. Young

 

[fest3er]

You have air in the lines. Bleed the brakes, RR, LR, RF, LF: generally furthest from the reservoir to the closest.

Since you had discolored fluid, you should bleed the whole system until the fluid from each brake runs clear. Brake fluid is hygroscopic; it absorbs water. Water causes rust. Rust is not nice to o-rings or cylinders, etc. , and may cause lines to rust out from inside. Water boils easily, which will cause sudden brake 'loss' under braking heavy enough to heat the fluid past water's boiling point. Brake fluid really needs to be changed every 3-4 years, or 80-100K miles at the most.

I had a '66 Gutlass (400, 4BBL, 2 Spd, dual exhaust) on which the brakes worked great. But if I almost lifted my foot off the pedal when stopped, the pedal would go to the floor disconcertingly fast. But moderate to heavy pressure would keep the pedal firm. This is a sign of a master cylinder that needs work.

 

[MAYoung]

Update: Front Disc Brake Change

Gentlemen:



Thank you again. The master cylinder has be changed out with an Autozone part that went for $53. 99 plus tax. I have no idea what the service life will be but it has a lifetime guarantee. In any event, the Dodge dealer would not have a new unit until mid-July and a rebuilt Dodge unit would not be available until 5 days out. The price of the Dodge dealer rebuilt unit was $82. 25. The price of the new Dodge M/C was about $185. 00 plus tax. (I would have preferred the Dodge rebuilt unit even with the extra cost. )



The brakes have improved. The pedal does not go to the floor when applied but there is a bit of sponginess to the brake pedal. I am going to test drive the truck tonight and then bleed the brakes in the morning. Hopefully the air bubbles will find their way to an convenient place to leave the system when bled.



I will keep you posted of my progress. This is real important since I taught my daughter how to drive the 5 speed so the brakes must be as close to perfect as I can get them.



Regards,



M. Young

Fair Oaks, CA

 

[MAYoung]

Update: Test Drive

The truck drove well. The stopping was smooth and balanced. No pulling to right or left. And the brakes do work well. The new fronts combined with the 2. 5 month old rears are nice.



Pedal does not drop to floor after application of brakes. Slight softness in pedal but even a light application of the brakes begins to slow the truck down. No need to push hard on the brakes. Release is quick and without hesitation. Greased calipers make a huge difference.



Will go after the last of the air in system tomorrow. I will keep you posted.



I did, however, lose a hubcap. Damn. Bike patrol tomorrow as well.



M. Young

Fair Oaks, CA

 

[MAYoung]

Update: Brake Function/ABS Light

Gentlemen:



First, the good news: I found the missing hubcap. It was in the weeds about a mile from home. I saw it, pulled over, went back to retrieve the cap and could not find it! It took another 3-4 minutes of searching to find the cap.



Brakes: The brakes work well. The truck stops smoothly and pedal action is fine. Just a small travel of the pedal and the truck begins to stop. Pedal action is firm. No noises, no pulling, no clunking.



ABS: I now have an active ABS light. It came on soon followed by the red brake indicator. It went out on its own but it is now back on.



For a short while, the speedometer did not function. It now works but the ABS/Brake light is on.



The Factory Service Manual tells me you need the Dodge scanner (DRB III) to access the fault codes in the ABS CAB. I cannot read them with an OBD II scanner.



I was going to bleed the brakes one more time to see if that helps otherwise I will have to go to a shop that has DRB III capabilities.



Any other suggestions?



Thank you in advance.



M. Young

Fair Oaks, CA



Today's weather: Sunny and clear with a high of 97 degrees. What a change from the high in the 60's and rain a little over a week ago.

 

[Mman]

Sound's like the rear wheel speed sensor die'd on you. My speedo and tach and ABS light did the same thing when it went bad. Do a search of the forum's on the rear axle speed sensor. It i'll give ya alot more info.