I have a 98 F-150 4x4 with a 4.6. I had gone to get some plants from a nursery down the road and on the drive down and back I had no problems. When I got back, I parked the truck for maybe an hour, then I got back in cranked and the brake peddle went all the way to the floor. I've had a few problems with my front left caliper locking up but I had taken it off and cleaned it and lubed and haven't had a problem since.

I got home today and decided to put new fluid in it and bleed the brakes to see if maybe any air in the lines. I bled the rear just fine but when I got to front it will not pump any fluid out. At the bleed valve it'll blow a little air out but it feels like it's sucking It back in. I put my finger over the bleed valve to make sure it wouldn't suck any back in but still no fluid. I'm thinking that maybe the master cylinder is just letting the fluid pass through internally. I just don't understand how it could just go out that quick.

I got the truck at 60,000 miles and for as I know it has not had a new MC put on it. Truck has 199,000 now.

Thanks for any input.

 

Yep, if there's no external leakage than a bad master cylinder is the likely culprit. It failed gracefully for you. Good truck!

 

if the pedal goes to the floor, something is leaking thru... master cylinder is the most common... possibly something in the ABS, but MC is most common.. no dash lights on ?

 

Yes, both ABS and the brake light are on.
When I buy a master cylinder should I buy motorcraft or will any of them do?

 

Tough call anymore. Buy new, not remanufactured though. Bench bleed thoroughly prior to installation.

 

I replaced the master cylinder today. I have brakes now. Yay! The ABS light is still on though, I thought about pulling the battery cable ,but I haven't done anything yet.

 

Probably have to download a new software patch or something. /s