Guys, be kind, I know this is a noob question. I had both front & rear brakes done about 8,000 miles back. The brake system was flushed at the same time. The last couple weeks, when I apply my brake pedal, the truck does stop just fine, but the pedal slowly keeps moving down until it bottoms out. I then have to let it up and re-pump it to feel any resistance. Even when it's bottomed out the brakes still work but I think something is not right as the pedal should not fade like that. Any guesses as to what the issue might be? I have checked the brake fluid reservoir and the level is fine and there is no squealing or other brake noise.. Thanks in advance.

 

Sounds to me like you need a new master cylinder. Brake fluid is seeping past the seals internally, allowing the brake pedal to slowly go down towards the floor board.

 

Yup,
Sounds like time for a new MC

 

Yep. New MC being installed. Maxcare lifetime warranty comes in handy. Thanks for the input guys.

 

Ok, The new Master Cylinder was installed. They did not do a bleed or flush of the whole system because that was not covered by the max care warranty and they wanted too much $ to do it. Also, the fluid was replaced 8000 miles ago when both the front & rear brakes were done so both I and the dealership agreed it was not a must to replace the fluid. However, the pedal still feels somewhat mushy...do you guys think a bleed/flush might take care of it? I do have a motive power bleeder and I could do it myself. Opinions?

 

I would tend to agree if flush was just done, there is no need to re do it. However, if you have a mushy brake pedal a bleed may be in order. Usually, most shops and good mechanics can install a MC and bleed the air right at the MC lines without bleeding the system at all four wheels. Again, however, if they have pushed air into the system, you may need to bleed at all four wheels. Or, you can try bleeding again at the two lines on the MC as a first step before going to all 4 wheels.

 

Ok, I am now starting to get annoyed. After taking it back to the dealer and having them tell me there must be air in the system AND again that a flush to get it out is NOT covered under warranty I did a flush myself and it did not fix the issue. I used a motive power bleeder and I did all 4 wheels until the fluid was clear and free of any bubbles and it took less than 1/2 of a quart. Started at rear passenger, then rear driver, then front passenger then front driver. I can see no way that any air got in while I was doing the bleed. If you're familiar with the motive bleeder you know it forces new fluid under pressure into the reservoir and you just crack the bleeders one wheel at a time and the new fluid pushes the old fluid out. When it turns clear and no bubbles you just close the bleeder. There is no pedal pumping and thus no opportunity for any air to get sucked into the system. Pumped the pedal half a dozen times before starting the truck and it felt solid. Started the truck and the pedal is still exactly the same as it was. Brakes work, but the pedal slowly keeps dropping until it bottoms out, especially when stopped at a light. So a new MC didn't fix and a thorough flush didn't fix. When doing the bleed there was no indication of any leaking fluid anywhere around the calipers and I have no drops or spots anywhere under the truck. What would be the next thing to look at? I'm considering just taking it to a different dealer but if anyone here has any thoughts I'd sure be appreciative.

 

Air in the abs module.

 

not sure what to tell you. Still sounds like an internal leak.....ie master cylinder even tho I know you replaced.

Air in system : usually mushy pedal and usually can pump pedal up. Let it sit and first pump...brake pedal will go to floor.... but you can pump it up. Pedal does not usually creep to floor with air in system.

Internal leak: under light braking pressure (ie stopped at red light) pedal will slowly fall to floor. (pressure on cups being forced against cylinder wall is light and fluid seeps past).Although, Under hard fast braking pressure pedal will usually remain as is - pressure on cups being forced against cylinder wall is high keeping a tight seal and stopping fluid from seeping past.

External leak is obvious. fluid will leak onto ground and pedal will drop to floor every time.

Not sure what else I can tell you, except good luck

 

P38.....Is that something a that would be a DIY fix or is it involved?