Disappearing brake fluid?

[dja4260]

2005 Suburban, as of two years ago the master cylinder, calipers, and all brake lines were replaced. Within the past 3 weeks, I've been quickly losing brake fluid BUT I find none on my garage floor.

Obviously, I have an issue with the brake system.


Any thoughts or ideas on how to diagnose which caliper is the culprit?

 

[NitroM3]

Well its leaking and you just haven't found the leak. Brake fluid does not evaporate.

 

[DuckRyder]

Does it have a vac booster?

 

[dbias]

Get it in the air and take the wheels off. Look for wet spot.

 

[dja4260]

Sounds like it's the brake booster after searching GM forums....

 

[Lubener]

You could pull the check valve out of the booster and see if it is wet with brake fluid. You can also loosen and remove the nuts which hold the master cylinder on. There should be enough slack in the brake lines for you to pull the M/C off the booster so you can check the rear of the M/C for leaking brake fluid.

 

[Astro14]

If you're not seeing wet spots at the calipers, or on the lines, it's likely the master leaking into the booster...from there, it gets sucked into the engine and burned.

That's not a booster problem, it's a Master Cylinder problem.

 

[nthach]

If the MC is leaking, kiss your brake booster goodbye. Brake fluid will swell the diaphragm in it.

 

[NitroM3]

Its always nice to have so many that run to the internet to find and recommend fixes.
There are missing Q&A to the OP before wild goose chases are done.

Lets at least start with how dirty the chassis and suspension is. Dirt can absorbed fluids and hiding their leaks.
Leak of brake fluid in the booster will destroy it as mentioned but you will also feel brake problem or ineffective foot to brake actuation if their has been a time period of more then a few weeks of the brake fluid in the booster.
Brakes are not to be questioned and generally speaking if you are asking then for the safety of all take it to a shop and get it inspected. After you get the result's of the problem then decide if you have the DIY capability to service the problem!

 

[Warstud]

Does the brakes work normal ? Does the engine run normal ?

 

[dja4260]

Does it have a vac booster?

Yes, it does.

Its always nice to have so many that run to the internet to find and recommend fixes.
There are missing Q&A to the OP before wild goose chases are done.

Lets at least start with how dirty the chassis and suspension is. Dirt can absorbed fluids and hiding their leaks.
Leak of brake fluid in the booster will destroy it as mentioned but you will also feel brake problem or ineffective foot to brake actuation if their has been a time period of more then a few weeks of the brake fluid in the booster.
Brakes are not to be questioned and generally speaking if you are asking then for the safety of all take it to a shop and get it inspected. After you get the result's of the problem then decide if you have the DIY capability to service the problem!

I'm dropping it off later today at a shop that I trust. 2 bottles of fluid in 3 weeks, not one drop on my garage floor...

Frustrating...

 

[NitroM3]

Yes, it does.


I'm dropping it off later today at a shop that I trust. 2 bottles of fluid in 3 weeks, not one drop on my garage floor...

Frustrating...

This is good info... and I commend you to take it to a shop!

 

[CharBaby]

Sounds like you have 4 wheel disc brakes however, IF you have drum brakes in the rear, pull the drums and check the cylinder under each rear drum.

 

[NitroM3]

IF(IF) you have drum brakes in the rear, pull the drums and check the cylinder under each rear drum.

You did read, OP's quote? "2 bottles of fluid in 3 weeks, not one drop on my garage floor..."

 

[Jetronic]

2005 Suburban, as of two years ago the master cylinder, calipers, and all brake lines were replaced. Within the past 3 weeks, I've been quickly losing brake fluid BUT I find none on my garage floor.

Obviously, I have an issue with the brake system.


Any thoughts or ideas on how to diagnose which caliper is the culprit?

check inside the booster, could be going throught the vacuum hose and burning in the engine

check inside the boots of the caliper pistons

 

[partspro]

Sounds like it's the brake booster after searching GM forums....

2nd Brake Booster.

 

[dja4260]

check inside the booster, could be going throught the vacuum hose and burning in the engine

check inside the boots of the caliper pistons

I believe you need a special machine to to bleed the system after a master cylinder replacement due to the ABS system. There really isn’t any point in me playing with it as it would need to be towed to be properly bleed.

 

[Jetronic]

No machine needed, but you need diag equipment to cycle the abs. The car is driveable without the abs being bled, but brake pedal travel is annoyingly long. Well all the ones I ever worked on were.

But just put something inside the brake booster from the vacuum port, cable tie is perfect. See if it gets covered in brake fluid.

 

[NitroM3]

Is anyone reading the OP comments? You realize a booster with the diagram volume capacity is less then what the OP is saying the brake fluid loss is right ? LOL

 

[Lubener]

Is anyone reading the OP comments? You realize a booster with the diagram volume capacity is less then what the OP is saying the brake fluid loss is right ? LOL

Doesn't matter. Engine vacuum will immediately pull the brake fluid out of the booster, into the intake manifold to be burned...LOL...