Dang near since new my truck has had an issue with a soft pedal. I have to pump the brakes twice to get proper preasure when stopping. The longer distance I drive, the worse it is. Took a trip to ST. Louis and I drove some 5 hours straight and went to exit off and had almost no pressure at all. Had to pump 3 or 4 times to get it up. Dealer has inspected and bled the system 3 times. It will be good for maybe 2 days, but it keeps coming back. I've tried having the system rebuilt, but the dealer won't do it without identifying the cause. Any ideas?

My guess is the master cylinder has a seal issue.

also another thing to check is maybe a connection/hose is cracked.

keep us posted it is interesting and could help out a fellow member in the future.

Between truck driver and my other projects, I haven't had a chance to go through the system myself yet. I have made quick explorations but have not found a leak and the fluid doesn't seem to be going down. I have had a thought if maybe one of the lines ends were incorrectly crimped and was letting air in but not fluid out. This is not unheard of, just expensive to fix. This is why I am trying to make the dealer do it. I rented an '07 QC 4.7 and it had great brakes. My 03 and 04 never had a problem either. Do these systems still run on vaccuum? Wonder if I have a leak there... Thanks for the ideas, keep them comeing please!

Had the same problem with my 07. You have to hook a scan tool to the HCU so you can cycle it. This is one place it can take in air without leaking fluid.You bleed all 4 corners, cycle the HCU, then bleed all 4 again.BTW, why is it not a warrenty issue?

It is. All they do is bleed the system and send me on my merry way.

It has to be your master cylinder or ABS unit is taking in air.

I would just keep taking it back until they fixed it right once and for all.

Is there another dealership you can go to?



Pup

If I can get my other truck running, I will run it over to Temple or Lampasas. It has got to get fixed before the warrenty is up. I just don't have the time to keep taking it back. I just don't know how to make them check the system better. Thanks for the ideas y'all. MJ

it's a seal on the piston that is allowing the fluid to bypass it and giving the illusion that it is air in the system. had this problem many years ago on a new replacement master Cly. how i finally figured it out was that the front of the reservoir would get low and the rear would fill up. (had a separate reservoir for front and rear brakes.) take it to the dealer ship and explain to them. that if they don't fix it and that you have proof that they worked on it and could not or would not fix it. that a lawyer will have them for lunch in a court of law when it fails completely and causes an accident. BTW it will fail completely just when you really need it to work the most.

how brake master cyl works here scroll down and you will see more examples of how they work.

Took it in today. They are suspecting a proportioning valve. However when they drove it they could not replicate the issue so it didn't get fixed. Go figure. On an up note, they did fix my rear window leak (again). There is a TSB on the sliding rear windows. They also reinstalled my seatbelts properly from the last time they did the rear window. And the saga continues.