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missing brake fluid can't find leak


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Can't change the topic title on my last post so starting a new one, I did get around to looking at the lines last night and I don't see a leak in any of them (haven't looked at the ones running from back to front, just from the wheels so far), as a matter of fact I can't see what the mechanic was talking about when he said the lines were rusty even. There is a bit of surface rust, but the armour (or coating) is intact, and I don't see anything serious in terms of condition, so I am beginning to think the lines are okay. I am wondering where else the brake fluid could be going, only thing I can think of is that there is something wrong with the master cylinder, but it would have to be an internal leak (there is no sign of fluid leaking anywhere externally anywhere on the car that I can see). Does this make any sense? It is the original part as far as I know so 16 years old now, the brakes have always seemed a little soft to me, but now they barely work at all (there does seem to be a little braking with the pedal almost to the floor). Am I probably on the right track, or should I be looking for something else?

Thanks

Scott

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In my first post I explained that the car had been sitting for a couple of weeks while I replaced the front driveshafts, when I tested it after installation I hit the brake hard to remove some of the light rust buildup from the rotors, the pedal went softer than normal, and I figured that one of the back brake lines (the hard ones) had burst since they were apparently rusty and ready to go (though I can't see any problems with them). In any case after the pedal went softer I drove it about 4km to get home, and bu the time I got home the resevoir was close to empty and there was very little braking going on (but still some at the extreme end of pedal travel). I have been replacing the timing belt and related components since so haven't had a chance to take a good look until last night (and haven't driven the car since the first incident), I refilled the resevoir and pushed the pedal a couple of times and checked for leaks, I can see no signs of leaks at any of the four corners (flexible lines or hard lines, or calipers) or under the hood, the level in the resevior went down maybe 1/4 inch after three or four trys, the pedal is still very soft. I couldn't really check for the leak the first day as the underside of the car was wet so couldn't see anything. At this point unless I can find an external leak the only thing I can think of is that the master cylinder is leaking internally into the booster, but I could be wrong. I just want to know if the could be any other cause before I go down this route, it would be easy if there were obvious leaks but....

Again thanks for any help

Scott

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the brake lines for the rear leave the master cylinder , enter the cabin and run along the floor at the rocker panel on the driver side to the back seat. there they exit the cabin, under the back seat, and go to a splitting block where a line goes to each wheel.

 

the most common location for rust through / leaking brake lines is where it leaves the cabin under the rear seat and goes to the split point. some , if not all, of this run is above the gas tank.

 

to find the leak, fill the reservoir and pump and hold high pressure on the pedal. keep doing it until the level in the master cylinder goes down. if the fluid level does not go down you do not have a leak. once it goes down enough, you will see fluid somewhere. probably under the car in front of the driver rear wheel, or under the rear seat.

 

did you work on the brakes at all when you were doing the axles? did you remove the caliper on either side? this can cause the pedal to have extra long travel when you first pump it.

 

as brake pads wear, the the fliud level in the master will drop. if the wheel cylinder piston is pushed back into the caliper during removal, the level in the master will rise. when the pedal is pressed the next time it will travel farther and use more fluid out of the master lowering the level. once the system has stabilized, the pedal should be normal and the fluid level consistent.

 

good luck.

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I'll be checking under the seat tonight, after I get the covers and stuff on to finish the timing belt replacement. I knew the lines went through the car, wasn't aware that they usually rusted in an odd place, hopefully that will be it, then I will be installing new lines and routing them conviently for me, then bleeding the brakes, it will be less expensive and hopefully less of a hassel then the master cylinder, just have to make sure that is where I am loosing the fluid. (of course I may die of heat exhaustion before I get to the brakes with the heat up here today). And I was able to replace the axles without removing the calipers, so that shouldn't be an issue thought I did check last night to see if I had somehow pinched a brake line, nothing I could see. Again thanks for the helpful suggestions from everyone.

Scott

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