Soft Brake Pedal Only on Hills

[snoborder42]

So for the past few weeks I've been chasing down these pesky brake gremlins and now its gotten even stranger...

So for the past few month my brake pedal has been softer than normal... Occasionally my ABS and parking brake light also come on, knowing that was caused by low fluid, i topped it off. Recently I've bled and flush the entire brake system, checked for leaks, and checked the adjustment on the drums. I've got no leaks, the pads and shoes are fine, but my pedal is still soft.

Now here is the strange bit I discovered today.... While stopping going down a hill my pedal is fine, nice and firm. But while on a flat road it is semi soft, and when going on an incline the pedal is super soft, I can put it almost to the floor.

I was kind of leaning towards a faulty master cylinder, but since my discovery today I'm completely dumbfounded to what it could be. Any ideas???

 

[huntman58]

I would say a Master still.

When you ran low of fluid did it look rusty and dark?
Have some grit in it when you flushed it?
Did it smell bad look feel ruff at all?

If yes to any of that then you may have a leak in the master.

 

[snoborder42]

Yeah the fluid was dark, not rusty colored just black. It was original fluid from 92 as far as i know. I know it hasn't been changed since I got it 6 years ago...

Yeah im still leaning on the master going out. Any idea how much it will cost to have it replaced??? I'm fairly mechanically inclined but this is way over my head...

 

[nexis]

Replacing the master cylinder is not too bad at all. Did mine in about a hour in my driveway. Got quoted around 200 to have it done in the shop, picked up the replacement from autozone for around 35 bucks, add in the brake fluid, and the flare nut wrenches, and i was still under 50 bucks. If in doubt, you can pickup the repair manual for the truck while you are there, im almost positive it walks you through it all. Just make sure to bench bleed the new cylinder before you install it on the truck, then bleed the system all throughout.

 

[huntman58]

As a fallow up even thou you know it, I will still say it, as I have even forgotten it!

Keep that brake res full at all times!

DO NOT LET IT RUN OUT OR YOU WLL HAVE TO START ALL OVER FROM THE BENCH BLEED ON!

 

[92exp4x4]

If you are going to replace the master, it is good practice to replace the wheel cylinders and calipers and rubber hoses at the same time, especially if this stuff is original equipment. The same garbage in the master will be in the bottom of the system as well. If you had to add fluid then it obviouly leaking somewhere. It adds to the cost and complexity of the job I know, but I take brakes very seriously.

If you can bleed brakes then you can do the other work. Its not hard. Be prepared to replace line ends and lines as they will probably be rusted in place and damaged upon removal.

Good luck

 

[huntman58]

If you are going to replace the master, it is good practice to replace the wheel cylinders and calipers and rubber hoses at the same time, especially if this stuff is original equipment. The same garbage in the master will be in the bottom of the system as well. If you had to add fluid then it obviouly leaking somewhere. It adds to the cost and complexity of the job I know, but I take brakes very seriously.

If you can bleed brakes then you can do the other work. Its not hard. Be prepared to replace line ends and lines as they will probably be rusted in place and damaged upon removal.

Good luck

Good advice! As a note why it is good I changed a master only one time and as I left my drive way I blew a wheel cylinder so changed it next trip blew a line. Well needless to say after that I changed every thing out and no more troubles. the car was a 1965 Chevy nova that I bought after it had sat in a garage for almost 20 years for $300.00 it was driven every now and then and only had 26,000 miles or so on it well all the rubber had creaked and or rotted out but most of it was from the inside out so you never saw it but it did make stopping fun as that car only had a one cylinder resave and the parking break was frozen. Believe me you do not want excitement like that at my age LOL