Help Diagnosing Brakes DRAGGING

[Florin1]

Hey guys. Think I'll start a new thread in my current issue. I'm chasing down my dragging calipers issue. I thought my initial problem was from my 5th wheel, but it's obviously not. That thread is here 

So here is the problem I'm experiencing. My front brakes drag hard. To the point where I can spit on my rotors and have the spit sizzle off. This is just under normal driving with very light brake application. Mostly highway. 

I thought I had siezed calipers so I serviced the truck this weekend only to find problem still there. 

Here's what I replaced. Bought new front calipers and pads, new rotors, and new brake lines, and on the rear I got new cylinders. Also new fluid flush. Bled brakes once I was done. Bedded new brakes properly. 

After two days of driving, I noticed I am still dragging. I'd like to get to the bottom of this before I screw up my new brakes. 

Heres my initial diagnosis. I notice if I depress my brake pedal, the pedal comes back up kinda slowly. It doesn't just snap back. I can also see my tail lights stay on for a second or two after I release brake pedal. With the truck off, I pumped the pedal a few times and hold it down with moderate pressure and then start the truck. Pedal sinks a little further, but doesn't "push back". That's as far as I made it. Thoughts? Thanks. 

[jlbayes]

Sounds like the boost or the master are dragging. I would be checking the booster first.

Edited March 29, 2017 by jlbayes

[JAG1]

When my truck was almost new (29,000 miles) I kept have problems with one caliper then another at different times always sticking, dragging the truck. Never heard of all four or two sticking simultaniuosly like yours.

 

Have you changed/ flushed your power steering fluid lately? it also actuates the booster to the brakes.

[IBMobile]

Check the Hydroboost for slow or incomplete pedal return:

1. Run pump at fast idle.

2. Pull the brake pedal rearward with approximately 10 lbs. force and release. Measure the distance to the floorboard.

3. Make 100-lb. brake application. Release brake pedal and measure distance to floorboard. The brake pedal should return to its normal position (step 2). If measurements are the same, go to step 5.

4. If the brake pedal does not return properly, check the pedal to be sure it is operating freely. Correct any sticking or binding as necessary.

5. If brakes are self applying and pedal is free, check for obstruction in the return line or a kinked connection between hydo-boost and pump reservoir. If obstruction or kink is found, go to step 6, otherwise go to step 7.

6. Remove obstruction or replace line as required. If condition remains, check for a damaged reaction end. If damaged the hydo-boost should be replaced or repaired.

7. If brake pedal is free of any binding conditions and return line is free of obstructions, remove the master cylinder cover.

 

8. Observe the brake fluid in the reservoir while rapidly depressing the brake pedal one inch.

9. Fluid surface should have some movement or spout in the forward reservoir section. Minor spouting may occur in the rearward reservoir. If no movement or spouting of fluid occurs in forward reservoir, the hydro-boost unit is defective and must be replaced or repaired.

 

 

[Florin1]

I have not flushed power steering. IBM I'll try those steps when I get home. 

Such better tips on this site versus CF. haha. 

[Dieselfuture]

I think people from CR form come here to educate them self so they can go back to CR forum and educate other people 

[Chris O.]

Quote

I think people from CR form come here to educate them self so they can go back to CR forum and educate other people 

LOL

[IBMobile]

 

4 hours ago, Florin1 said:

I have not flushed power steering

 

[Mopar1973Man]

Another rare thing is the brake hoses coming part internally and creating a one way valve which will make the brakes hang up. Excessive debris in the system can hang up calipers causing the pistons to stick. Hydrobooster is possible from old fluid and debris causing it to hang in apply mode slightly. All are caused from lack of fluid changes on powering fluid and brake fluid.

[Florin1]

Ok. So IBM, I went through your checklist. Made it to 7.  I don't seem to get fluid movement in MC. I took 2 videos I'll attempt to post. One with engine off, rapid press, then eng. on rapid press. 

Engine off

ENg on

 

Also, another curious thing I noticed is my cap's little rubber diaphragm is extended out. I pushed it back in yesterday, and today, it's out again. 

 

[Florin1]

Anyone?

[Mopar1973Man]

Fluid is dark and nasty again.

 

As for the rubber no biggy. Rather normal to see that happen.

[Florin1]

Probably cz I'm cooking this fluid too. Haha. But it's actually not that dark. 

[IBMobile]

I don't think you can cook brake fluid like you can trans fluid and the rubber in the cap is OK.

I got the same results in the brake fluid reservoir that you got when steeping on the brake peddle, no fluid movement observed.

On ‎3‎/‎29‎/‎2017 at 7:22 AM, Florin1 said:

I notice if I depress my brake pedal, the pedal comes back up kinda slowly. It doesn't just snap back. I can also see my tail lights stay on for a second or two after I release brake pedal.

This is from the FSM                                                                                                                     page 5-18

           CONDITION                             POSSIBLE CAUSES                                    CORRECTION

Slow Brake Pedal Return        1. Excessive seal friction in booster.                  1. Replace booster.

                                                 2. Faulty spool valve action.                              2. Replace booster.

                                                 3. Restriction in booster return hose.                 3. Replace hose.

                                                 4. Damaged input rod.                                        4. Replace booster.    

 

On ‎3‎/‎29‎/‎2017 at 7:22 AM, Florin1 said:

With the truck off, I pumped the pedal a few times and hold it down with moderate pressure and then start the truck. Pedal sinks a little further, but doesn't "push back".  

BOOSTER FUCTION  TEST                                                                                                               page 5-17

With the engine off depress the brake pedal several times to discharge the accumulator. Then depress the pedal using 40 lbs. of force and start the engine.  The brake pedal should fall and then push back against your foot.  This indicates the booster is operating properly.  

I think you have a bad booster and the problem may be the spool valve is binding.

 

Edited April 7, 2017 by IBMobile

[beren]

Brake fluid is hydroscopic and it will absorb a lot of water, then rust out your lines and calipers from the inside out. Manufacturers used to call for yearly break fluid flushes, they cut back because the cost of dealer maintaince, just like they went to platinum plugs because they last 100k miles, even if they give poorer spark. Also the more water in your fluid the lower the boiling point and easier to hit brake failure temps.

 

Sometimes master cylinders fail and need new seals/replacing, or like mopar said, rubber lines collapse and they won't let the fluid out of the calipers...

 

What ended up being the issue?