Intermittent brake drag

[99_6speed]

Hi everyone,

I am a refugee from Dieselstop so please pardon my lame post count!!

I am having an intermittent problem with my rear brakes. As I am driving along (I can go 200 miles and never have a problem) I will feel the truck starting to drag, EGTs go up as does the boost as I try to maintain speed. I am assuming it is the rears because it is not pulling at all to one side or the other. I thought it was the slides but I cleaned and lubed them up. The pads were getting low so while I had it apart I replaced the warped rotors and pads with NAPA Gold parts. The problem persisted so I have replaced both rear calipers. Unfotunately I still have the problem.

Could one of the brake line hoses be "valving", dirty fluid??

Any thoughts would be appreciated!

John

[99_6speed]

Sorry for the bump but I really don't want to keep throwing parts at this!

Any thoughts would be appreciated.

[TennesseeDuck]

I have seen rubber brake lines deteriorate internally and "valve" as you put it. Both times I saw it was on the driver front of 2 different Jeep Cherokee's. I would check the condition of the rubber hoses. If you replace the rubber hoses it would be a good idea to flush the brakes lines out with fresh clean brake fluid. DOT 3, 4, and 5.1 brake fluid contain glycols which are hygroscopic (absorb water from atmosphere) which deteriorate brake lines from the inside out as well as degrading the hydraulic efficiency of your brake system. Usually if it is a rubber brake line they do not do it sporadically, once it starts it usually doesn't abate until it is replaced. IRC master cylinders have a check valve in them too. Might be worth a look into the master cyl to see if you can see any debri in there.

[99_6speed]

Thanks for your suggestions- I will do both of them. Do you think I should use standard hoses or go braided stainless?

John

[TennesseeDuck]

The choice of brake hose is yours but I wouldn't spend a lot for braided stainless unless I towed a lot of heavy weight or felt the need for the extra strength. All brake hoses have to be DOT approved which is why you can't go to just any hose shop and get them made, its a big no-no with DOT and most shops won't risk the fines or liability.

[TennesseeDuck]

"Compensator Port Check

The purpose of the compensator ports in the brake master cylinder is to supply any additional brake fluid required by the system due to brake pad wear and to allow brake fluid returning from the brake lines to the brake master cylinder to enter the brake master cylinder reservoir.

The returning brake fluid will cause a slight turbulence in the brake master cylinder reservoir. Turbulence seen in the brake master cylinder reservoir upon release of the brake pedal is normal and shows that the compensating ports are not plugged."

This is from the service manual.

[99_6speed]

thanks again!!

[TennesseeDuck]

Did you locate the problem?

[99_6speed]

Not yet- it is this weekend's project!!

[dumokie]

Are you saying the e.g.t. and boost, drag occur when your driving at speeds without applying your brakes? Or does this drag happen after you have applied brakes while driving? It sounded to me by your description that it occurs as your driving along... Can you expand a little??