99 Ram 4X4. I changed front brake pads only. They were very thin,but they still stopped and were braking well. I cleaned and lubed all parts per instructions, test drove and the brakes worked perfectly, Hard, braked straight, no pulse or wobble or pull. I drove around a day or two and had no braking problems. I then parked the truck for about one week and as soon as I got back in and started backing up, the brakes sank almost to the floor and the ABS and Brake lights came on and now i have to pump them up and they never get hard again but do not go all the way to the floor but keep sinking. I have not seen any leaks around the wheels or lines....any ideas are greatly appreciated.

 

Probably needs a new master cylinder.

 

Check the rear brake line near the gas tank. They are notorious for rusting out and leaking behind the gas tank (along the frame rail) where you can't see it well. Might need good lighting and an inspection mirror to see it properly. You could also have a master cylinder that is going bad, too. They sometimes leak out the back and into the brake booster. Are you low on brake fluid in the master cylinder reservoir? If so, that's a good indication of a brake system leak somewhere.

 

Hey thanks for the info... You were right....it was a torn rubber boot on the brake cylinder...I just got done replacing it and will bleed the whole thing tomorrow...just in time before the snow and cold sets in here in minnesota...

 

definitly needs a master cylinder

 

I hope that's not it... But on a 99, could be that... I was able to replace the brake cylinder on the rear wheel, cleaned all the brake gunk off it, struggled to put everything back together and replaced some brake hardware and finally got it fitting correctly... But got too cold so I'll bleed them tomorrow and see... Thanks for listening to me..

 

Turned out to be the brake cylinder rubber boot ruptured... Replaced that, bled all four wheels... Brakes work fine... But now the ABS and brake lights stay on...any ideas about that??? Thanks again for listening to me..

 

Need to pull the ABS codes. There should be a procedure listed in the service manual for your year truck. There was another thread on here about pulling ABS codes about a week or so ago that you might find helpful, too.

 

Probably the proportioning valve is out of position.

 

Ok... I'll look into those things and report back... thank you