I have a dilemma., But it's not my dilemma. Options

[Jessie]

The quick run-down:

-2005 Chevy Silverado 1500 HD 2WD V8 w/Towing
-Recently went through a brake/suspension upgrade.
-My roommate tows her horse to shows almost every other weekend.
-She's had this issue that we recently have just "fixed". and by fixed, I mean we topped off her brake fluid.

See, she has a slow "leak," meaning that she's losing brake fluid but we haven't found a leak. Neither has her father, or her mechanic. Every few weeks to a month, she'll brake, and when she does the "Service Braking System" lights up red. We just top off the brake fluid and we're good to go for another few.

I know this information is very vague, but does anyone have any sort of idea as to why she's losing the fluid so fast? And with no "leak" to be found? We've let her truck sit and idle while pumping the brake every couple of seconds or so, then watch. Nothing.

It's a bit scary as she's always towing her horse, and if her brakes fail it would be disastrous.

Thank you in advance for your ideas!

Jessie

[Brad M]

I'm guessing at this, but could there still be air in the system? it may just be slowly making it's way back to the MC now. Otherwise, only other thing I can think of is it's boiling out.

[Jessie]

Let me add that the upgraded brakes happened about 2 years ago. :/

[afob3]

How low is the fluid getting over what course of time? Or how much does it take to top it off? Has the system been completely drained & refilled with new fluid? In RV's it is common for the fluid to sit too long since they aren't driven often. It collects moisture that boils off under the heat of braking causing what appears as low fluid and the loss of braking power.

I hope the trailer she is using has brakes whether electric or hydraulic.

Gut reaction is to find another mechanic. That much fluid loss has to be leaving some stains somewhere if I'm wrong about very old fluid.

[Jessie]

In about two months, it goes from the maximum to minimum line in the reservoir. She drives it every day, and there is no real loss of braking power. As for bleeding the brakes, it was done after the upgrade, and before she bought the truck.

Her trailer does have electric brakes.

[mlumz]

I would bleed the entire brake system then see if that helps. Also by doing this you, also double check on the brake lines and connections. Also I'm leaning to something going on with the master cylinder if the bleeding doesn't solve the problem.

[RPW00Mirage]

as the brakes are worn, the fluid should go down.... but not at that rate.

it may be worthwhile to trade up to a better fluid just incase if you cant find any leaks, weeping and whatnot. on a truck like that, is the entire brake line system exposed? or is it run through the chassis?

[Tyler]

I would bleed the entire brake system then see if that helps. Also by doing this you, also double check on the brake lines and connections. Also I'm leaning to something going on with the master cylinder if the bleeding doesn't solve the problem.

^^^this is a great place to start^^^

[Vinnie]

I had a similar issue with my Avalanche. I re-did the brakes. Rotors, pads, hydraulic hoses, dust shields and new calipers... had some leaky issues but couldn't find out where it was and it didn't leave any damp spots where I parked.....

BUT

The front right wheel well told me where the leak was.... shiny oily splatters on the shield of the wheel well... turned out I needed to tweak the bleeder screw a quarter turn on the caliper.

The hoses if leaking would leak onto the suspension components... would be very visible if you get under there. It would look oily and slick.