mullishacrew

hello, well i just got home from driving for a couple hours and when i went to park my truck in the drive way i pushed the brake and then applied force and the brake pedal sank to the floor not quickly though, could this mean my master cylinder is beginning to go? or possibly i have a bubble in one of my rubber brake lines? there is no brake fluid what so ever under the truck and i never had this happen before and the brakes work fine, any suggestions?

harvy

fill it up and keep an eye out

MBolivar

The symptom you described sounds like a master cylinder going south. The seals are notorious for leaking internally and it's accredited to the heat that the diesel engine emits. A bad caliper would cause the same symptom but I would look into the master first.

14racing

Sounds like the master cylinder to me too. In fact i have even had trouble with re-mans doing that. Took about 3 of them to get one that worked right.

nocky

with the core charge sent back a reman came to less than $30 easy fix

bigbaddiesel416

mine did this and the rear wheel cylinders were leaking and was not detected the rear section of the master cylinder was out of fluid and it still stopped but the pedal was real squishy

ebteckx

I have had new and rebuilt masters go bad. Side note, since its losing fluid this may not apply to you but when mine had similar symptoms the rwal unit failed. bypassed it and had perfect pedal... you wouldnt believe me if i told you how many times i bled that system... good luck!!! ps napa rebuilt mc was the one that finally worked for me.

MBolivar

Good that you had mentioned that. Mullishacrew, does your RWAL system work? If that dump valve is bad, it will have that same feeling at the pedal. Bypassing it is easy and the parts are available from NAPA or other parts store. Some here will argue to leave it be if it works while others have had problems and bypassed the system to avoid the 300 some odd dollars for a reman unit.

mullishacrew

i bypassed it 3 years ago, i wasent going to deal with that thing ahah, but ill keep monitoring it, thanks guys!

Yreka

Anyone ever see a dumpvalve go bad in this manor and not throw an ABS code ?

Im having similar issues, but no ABS light. I may just need to keep doing the reman shuffle.

wannadiesel

Yes, I don't think anybody who has had a bad dump valve got a code from it.