Brake fluid loss


Dedicated LVC Member
May 8, 2004
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Tuxedo, NY
Before I tear into it, I was looking for any input on usual places (yes I've searched the site) to look for a brake fluid leak.

Background - 2000 LS driven by me for over 10 years on heavily salted roads. Last weekend the brake pedal went soft and the warning light came on. I topped up the reservoir (it was very low) , pumped the pedal (I was 300 miles from home when the failure occurred) and everything was fine. I kept an eye on it and I have a leak somewhere (needed to be topped up once on the ride home). The car is off the road until I can look at it. Since the pedal only sinks slowly it is not a completely ruptured hose or a complete rust through on a tubing bend.

I plan on looking at all the fittings and if I find nothing then to the calipers and finally to the master cylinder (both the fittings and in the brake booster). Since these things rarely only happen on one vehicle, I'd appreciate input on any places others have found a slow brake fluid leak on an older LS.

Thanks (I will not get a chance to get under the car until next weekend at which point I'll post what I've found).
Mine did the same thing last year in the summer time. It was the rear passenger side caliper. The seal wore out causing brake fluid to slowly fall and burn up before it hit the ground causing it to leave no puddle of brake fluid on the floor. $140 later I still don't have any problem other than the spongy brake pedal. Not too sure if this is how the LS was made.
There's gotta be a leak ?? Especially if you have to consistantly add fluid.
...IMO... a "ruptured" hose or line, would have the outcome for two things to occur:
(A) A specific location point for Brake Fluid loss to occur and (B) The introduction of Air in a pressurized system.

If no leaks are "visually" present on the lines then I would assume your Master Cylinder has the issue (internal seal) !!!
But as you said (rarely occuring) and fudge12 confirmed for his bad seal issue. Although, not so sure
about it burning or evaporating prior to reaching the ground. **Verify that no rips, or tears are present on the rubber
boot/seal on the caliper assembly when it squeezes the pad (This is the last thing I'd check because at this point you'd
have to remove the caliper from the rotor/pad and (squeeze) open to properly expose the caliper boot/seal for inspect).

So it's gonna lean more to... a leak somewhere in the system (after the Master Cylinder) and therefore the introduction
of air in the system also. I'd crack each line (one at a time) before the caliper and step on the brake to make sure that
fluid does in fact squirts out that line. Retighten the line and move to the next brake line. -For me this would verifiy that
there was no obstructions (in that specific line being checked) prior to reaching the caliper). -But that's me.
One thing to remember is if you have to add more fluid then what's coming out the line then that's not where your issue/
problem is occuring...

My apologize...I'm kinda all over the place with my answer but hopefully you get the "jist" of it...
My 2 cent "jist" at 3:33am (local time) ===>:p
...I plan on looking at all the fittings and if I find nothing then to the calipers and finally to the master cylinder (both the fittings and in the brake booster). ...
I'm betting on it being a caliper, but one thing to check that you didn't list would be the ABS assembly.
I might have an extra brake booster laying around. Bought it used when I re did the master cylinder and booster. It's from an 00' v6 with IVD (AdvanceTrak).
Left rear caliper was leaking from the spindle for the parking brake lever enters the caliper. I found the left rear tire coated and after applying the brakes with the wheel off found a small puddle under where the parking brake cable attaches to the caliper.

I just installed this caliper in August. I had changed both rear calipers because they were rusted, dragging and had damage pistons. New one is on order and I will tackle the repair on Wednesday.
Went to replace rear rotors today...and holy ****. Puddles on the insides of both rear rims...wut tha..? Right side was replaced 6/13 so I only have to pay for left side caliper..right will be free. Been adding fluid for about a month..but didn't know where it was coming from..the pads on the rear look like they came from a Duncan Hines fudge recipe..smh. Two calipers and new pads in the morning..instead of griping about the repair costs..I just picture the smoother ride after the

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