The wife and I bought a 2003 F150 for when we or one of our kids needs a pickup. It's in great shape and runs fantastic. The master cylinder is getting a bit mushy and needs to be replaced. I checked the bleeder valves at all four corners and a couple of them seem really corroded. I think they will break off if I just try to open them for bleeding. I have been putting penetrating oil on them for about 24 hours. Is there any other prep work that I can do to help free them up or should I just plan on replacing the calipers if one breaks? I've "you tubed" the hell out of this and there are tons of things to try but none seem "guaranteed". Some real life experience would be nice.

Edit:
Oh, one other question: I came across a bunch of videos about "gravity bleeding" the brakes. Does that really work or is the pump-hold-release a better way to do it?

Use a very good quality socket when you attempt to open them.

I would ensure to use box ends on the fittings for sure. You can try Kroil applied liberally as well.

Some heat on the caliper at the bleeder would help too.

The torch, quality socket, and penetrating oil combo worked... I got all four cracked. Now to do the work.

You may even consider replacing the bleeders.

Gravity bleeding can be hit or miss, I wouldn't ever go with just this. Go with the tried and true pump and hold.

pump and hold.

Six point socket, or a tubing wrench.

Spray them with PB Blaster. Get a good 6 point socket and a cordless impact. Lightly pull the trigger so they get a good impact. Don't just pull the trigger and hit them full blast.

I would either clean up the bleeder or replace them, use antiseize on them before re installing.

quote:

Originally posted by Bytes:
The torch, quality socket, and penetrating oil combo worked... I got all four cracked. Now to do the work.

That would be what I would have told you. We have a 99 & 04 old body style

Didn't see it done but I worked with a former mechanic once. The boss had brought the MC cylinder to work they went out to change it and were back in 10 mins. It is possible to change without having to bleed everything.
Maybe a real mechanic can chime in as to how.
It think what he did was unbolt old mc with lines still attached. Bolt up new mc and bleed it then quickly transfer lines over with someone pushing break pedal while tightening brake line nut.
Probably harder with less clearances in newer vehicles.

quote:

Originally posted by Mikito:
Didn't see it done but I worked with a former mechanic once. The boss had brought the MC cylinder to work they went out to change it and were back in 10 mins. It is possible to change without having to bleed everything.
Maybe a real mechanic can chime in as to how.
It think what he did was unbolt old mc with lines still attached. Bolt up new mc and bleed it then quickly transfer lines over with someone pushing break pedal while tightening brake line nut.
Probably harder with less clearances in newer vehicles.

Yes you can bleed just at the master cylinder. Pump and hold, crack the line at the master. Do this to both lines until all air is out. However, it is better to change all of the fluid in the system.

The most reliable and easiest method I've ever used for bleeding brakes is as follows.

1) Remove all the bleeder valves and apply a heavy wheel bearing grease to the threads on all 4 valves. This acts as a seal to keep air from bleeding back into the brake cylinder through the threads when the valve is open.

2) Fill a clear container with about 2 inches of fresh brake fluid.

3) Take a flexible vinyl tube that is a tight fit on the bleeder valve and snap it on the valve and put the end into that container of brake fluid so that it's submerged.

4) Open the Bleeder and pump the brakes until you no longer see air bubble in the fluid you are pumping into that container. Then tighten the bleeder valve good and snug.

5) Repeat at all 4 brake cylinders while insuring that you don't run the master cylinder dry or overflow your catch container. When finished top up the master cylinder and you are done.

The post above is how I have always done it.

^^^^^
Same here especially on a clutch slave cylinder.

^^^ Same here with one exception.

I open/close the bleeder while someone else works the brake.