john9721

Hey guys, I've got a strange brake fluid problem on my 2004 F150. This is the 2nd time this has happened where the brake warning light has come on the dash, and the brake fluid level has been low. The first time, I added about 3/4 of a bottle and have it a few days to look for a loss. That was probably almost 2 months ago. It came back on last night as I pulled into my neigborhood. I had previosuly had the level even with the FULL mark, and it is now below the LOW mark. No sign of fluid on wheels that I've been able to see, but I'll climb under it again tonight to be sure. Doesn't seem to be a master cylinder leak at the booster, although I've heard of it possibly leaking into the booster...? Help me out please! Thanks!!

screamineagle

Sounds like the master cylinder is shot.

john9721

Do I need to worry about it leaking into the brake booster?

Hanginten24

I wouldn't say one way or the other for sure about leaking into the booster, however, I know this seems like a dumb question, but have you looked to make sure ur pads/rotors are in good shape? I had to add fl. like that once or twice and just out of curiosity, I looked at my pads, and they were EXTREMELY worn and needed replacin, I figured maybe as there was less and less pad, that the truck had to advance more and more brake fl. into the lines to push the calipers that much further? Not sure as I'm not a mechanic, but have had no problems toppin off fl. since I threw on new pads all the way around, just glad my pedal never went straight to the floor/ my rotors didn't get ****ed up, I'm sure someone will correct me on this, but just throwin it out there

techrep

iTrader: (1)

It’s going somewhere in the system...it’s a sealed system...if it’s not leaking out a brake line or caliper...it’s gotta be in the booster.

Mod (Ret.)

What techrep says. Brake fluid does not evaporate, so if you cannot see it anywhere around the wheels or brake lines, then it has to be dumping into the brake booster cavity.

john9721

If that's the case, will a new master cylinder do it? Or am I needing a brake booster as well?

F150Torqued

[MENTION=128179]john9721[/MENTION]


I can tell you, from first hand experience with my 2004 F150, that [MENTION=13845]techrep[/MENTION] and [MENTION=9045]Bucko[/MENTION] are correct. I fretted over the same issue for a year and half wondering where the hell my brake fluid was going without a trace. I SWORE the Booster could not possibly hold as much as I had added.



When I removed the old master cylinder - I stuck a 1/4 inch plastic tube into the booster, dropped the other end to the ground and syphoned out I'll bet you more than a gallon. I COULD NOT BELIEVE the booster could hold THAT much liquid and not drip it on my carpet.


I just replaced the whole master cylinder instead of a rebuild kit. I don't remember it costing that much. It got a little messy because I put the new one in a bench vice, filled it with fluid, placed a couple of fingers over output holes and used a screwdriver to pump / prime it to get all the air out, then ran installed it / hooked up the lines right quick. I didn't even have to 'bleed' the system - and it worked just fine. No need to do anything else to the Booster.


And afterwards, the brakes took less "peddle pressure" too! Hope your experience is equally as positive as mine.

Mod (Ret.)

Most new/rebuilt master cylinders come with two plastic fittings with clear hoses that you attach to the output holes of the master cylinder, and then route their hoses to the two cavities of the master cylinder. Then with either a screwdriver as F150Torqued stated, you can "bench bleed" the master cylinder by holding its base on a vice, and use a screwdriver to push in and release the piston that the rod from the booster/brake pedal operates.

I prefer to simply install the master cylinder on the booster, fill both cavities with clean brake fluid, and use the brake pedal to bleed it; just install the plastic fittings with the clear tubes onto the master cylinder, have a wife/girlfriend/significant other/buddy push on the brake dedal while you hold these lines over the brake cylinders cavities until fluid is flowing. Then remove the plastic fittings, and reconnect the hard lines.

At this time, I'd also do a complete bleed at all four corners, starting with the furthest point from the master cylinder (passenger rear), then drivers side rear, then passenger side front, and ending up with the closest (drivers side front).

F150Torqued

[MENTION=9045]Bucko[/MENTION] Thanks for filling in the info vacuum I left for [MENTION=128179]john9721[/MENTION]
I did some research and see plastic tubes you're talking about. Just my luck that I get some damn opened package without all the parts.
I would bet if I went back to the parts place and asked about it - he would look just like your AVATAR!! Lol