2004 Ford Expedition XLT Sports Utility - Where is all my brake fluid going??

[tripaphonic]

Hey there community. Thanks for having a place to post questions.

Just bought a used 2004 Ford Expedition. As soon as I got in the thing the brake pedal went to the floor. Very soft. I could still stop but I had to stand on it. The brake light came on and the low brake fluid light came on. I checked it and found the reservoir nearly dry. I stopped off and grabbed a couple of 12oz bottles of Prestone DOT 3 brake fluid. It took nearly both bottles to top it off. Started it up, the pedal was still soft but not as much as before. Headed home and it did the same thing ... brake light, low brake fluid light, and standing on it to stop. Stopped again to grab 2 more 12oz bottles. I used both of them to top it off, again. This time I left the reservoir cap off, started the truck, and slowly press the pedal over and over to see if there was a difference. The pedal was definitely less soft and add the resistance that I would expect if it were working properly. Started home again after a few stops it started doing the same thing. Dead pedal. I inspected the underside of the vehicle, the brake line, around each wheel, the reservoir & the master cylinder; no noticeable leaks and no wet surfaces.

I just bought the vehicle a few days ago and inherited the problem from the previous owner. They had it parked for a while and offered no insight ... go figure.

Thanks in advance for any replies.

 

[tommyddsr]

It has to be leaking somewhere on the line route. Start at the master cylinder, then the ABS module, all four lines to each brake hose, the hose itself, the where it goes to the calipers. Then check the seals in the calipers around the caliper pistons. There is no other place for it to leak. Losing that much I cannot imagine not readily seeing the leak. Check down the entire line as the steel lines on older Expy's do rust out. It only takes a small hole in the line. And a word of advice, never leave the reservoir cap off. If dirt gets in there you will be flushing your lines to get them cleaned out. Although it sounds like flushing may be in order as part of your repair. I'd do it to be on the safe side.

 

[Vincent Vega]

That does seem weird, although I do not know the brake fluid capacity. I did a full bleed on my front brakes a few months ago and went through about 20 oz. The rears will take more than that.
Other than that, check the ABS unit that tommyddsr mentioned. It is under the hood, driver's side, just behind the headlight. Looks like a black box with steel brake tubing. And/or, get underneath and trace the brake lines front to rear, see if there are any leaks. Maybe there are nooks or places where brake fluid could collect and not hit the ground for some reason. Good luck.

 

[tripaphonic]

tommyddsr & Vince V "my man in Amsterdam" : thanks for the prompt replies guys. I greatly appreciate you taking the time to help me out. I agree there has to be a leak somewhere because 48oz of brake fluid is missing. Although I suppose it could be pooled somewhere I can't see ... but I doubt it. I've also read about the increased possibility of lines rusting the older the vehicle but I'm sure that also has a lot to do with where you live. I wish we got enough snow or lived close enough to the beach to have to worry about salt but yeah, that's not the case.

I'm going to go back over the entire system again, a bit more diligently this second time. If there were any holes, no matter how small, would there not be brake fluid seeping out or at least a wet spot from where it was leaking? I mean, it is certainly possible to lose 48oz of fluid in such a short amount of time with no trace as to where it's gone ... but it does not seem very probable. Odd.

Good call on keeping the cap on. I've made that mistake before on the 1999 Durango I used to have. The entire system ended up contaminated. Granted, I was planning on flushing the entire system anyway but still. This time, I made sure to clean the cap & all around it prior to taking it off. Regardless, limiting the amount of time the cap is removed from the reservoir is the best and only way to limit anything other than brake fluid from sneaking in.

I'll keep the thread apprised of my progress and what I find. But honestly, what I'm thinking about doing is cleaning it up a bit more than it already is, taking better pictures, writing a more detailed description containing ALL the issues & relisting it for $1000 more. LMAO ...

 

[Hamfisted]

I wonder if it's running into the power brake booster chamber and getting sucked into the motor through the vacuum line ? Weirder things have happened ....
Pull the brake booster's checkvalve out (has the vacuum line attached...) and inspect it for traces of fluid.

 

[Lee_H]

Hamfisted I think has it. I suffered through a brake line break in the rear line. Same sort of feeding brake fluid while driving home. If nothing is on the ground, it is the master cylinder leaking past the back seal and getting sucked into the engine vacuum line. You will not see a leak until pulling the vacuum line and having it wet inside.
I have an 1971 Torino which was my first car. It had the same leak only no power booster. (Manual drum brakes around, prayed during rain storms) The carpet near the brake pedal would be soaked with brake fluid instead, no leak on the ground at all.
Best would get a new (not rebuilt) master cylinder and replace the vacuum line as well.

 

[JamaicaJoe]

That's it, gotta be the vacuum booster unless squirrels are under the hood drinking the stuff.

I hope the catalytic convertors are not bothered by the stuff. I have heard that silicon spray should not be used around a running engine intake for that reason.

 

[GAINMOB]

master cylinder...brake booster...abs module...hole in lines

 

[Fastcar]

That's it, gotta be the vacuum booster unless squirrels are under the hood drinking the stuff.

I hope the catalytic convertors are not bothered by the stuff. I have heard that silicon spray should not be used around a running engine intake for that reason.

Well... Was that the solution????

 

[dcsang]

I wonder if it's running into the power brake booster chamber and getting sucked into the motor through the vacuum line ? Weirder things have happened ....
Pull the brake booster's checkvalve out (has the vacuum line attached...) and inspect it for traces of fluid.

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