Brakes

[Salvador Alasco]

I have a 2001 Chevy Tahoe which ABS electro-hydraulic control unit was recently replaced. It is okay now. Recently however, I noticed that my brake fluid in the reservoir goes down every time I used the truck, so I always have to top it off.
I read from manuals (and please correct me if I am wrong)that this may be due to a used up brake pad(s), used up rotor(s), or both. If it is either one (or both) and I decide to change either one (or both), do I need to bleed the brakes after replacing either pad or rotor (or both) ? Will the bleeding procedure be the same with vehicles without the ABS ?
If it is not either the pads or rotors, what other reasons are possible for the brake fluid level to go down without any traces of any leakages ?

Thanks,

Sal

Topic

[college man]

The brake pads coming to the end of there life will cause the fluid
to go low in the reservoir due to the piston having to extend so much.
Pull the caliper or you may be able to view through the caliper to see
how much pad life is left. The bleeding procedure is the same and I would
recommend changing the fluid and open the bleed screw while resetting the
caliper. otherwise you have a leak somewhere.

http://www.ericthecarguy.com/faq/solving-brake-problems

[EricTheCarGuy]

As College man stated, brake fluid level will decrease as the brake pads wear. What you describe however sounds like there might be a leak somewhere. If that’s the case you want to know sooner rather than later. I would pull all 4 wheels and get at look at all the brakes to make sure there aren’t any leaks. If there are leaks, address them ASAP, and bleed the system after the repair. Then monitor the fluid level to see if you’ve repaired the problem. Additional information can be found in the article College man posted for you.

Good luck and keep us posted on your progress.

[Salvador Alasco]

I have checked my brake pads (like college man above had suggested) and also looked for possible leaks along the brake lines and those going to the wheels themselves. There were no evidence of any leakes at all. They were all bone dry and the pads were still okay.
Still, my brake fluid level keeps going down (though not as fast) so I have to top it off everytime the level goes down to at least 1/4-inch. I mean I wouldn’t want to find out how low it will go as topping it off alone every time it goes down tells me there is something wrong somewhere.

Any other ideas ?

Thanks,

Sal

[Lorrin Barth]

As pads or rotors wear the master cylinder fluid level goes down slowly. The master cylinder reservoir is sized to accommodate this wear. By the time you get warning light due to low fluid the brakes are due for replacement. In other words, you have a leak. Since it wasn’t leaking before, I’d suggest looking where the work was done.

[Salvador Alasco]

Though my brake feels okay (not mushy, if there was a leak where the work was done, will it necessarily follow that air must have also gotten into the brake system ?

Thanks again,

Sal

[Bill]

The brake fluid has to be leaking somewhere. If it’s not an external leak then it’s possible that the master cylinder is leaking into the power brake booster. Remove the master and inspect where it bolts up to the booster for wetness there.

[EricTheCarGuy]

[quote=”wysetech” post=110166]The brake fluid has to be leaking somewhere. If it’s not an external leak then it’s possible that the master cylinder is leaking into the power brake booster. Remove the master and inspect where it bolts up to the booster for wetness there.[/quote]

+1

I was actually going in this direction before I read this comment.

If your brake pads are good as you say, and the fluid keeps going low, then there is a leak somewhere. Brake fluid is not like motor oil that can be burned within the engine, if brake fluid gets low, there is a leak somewhere. Try disconnecting the master cylinder from the brake booster, you don’t have to open the brake lines to do this, they will bend enough for you to move the master cylinder far enough away from the brake booster to get a look inside. If you see fluid in the brake booster, replace the master cylinder and recheck for the problem.

Good luck and keep us posted.

[Craig Robinson]

I am helping a friend with a problem similar to this. No obvious leaks and the brake pedal settles to the floor. I refilled the brake fluid reservoir and when he restarted the engine on the truck, roughly half of the brake fluid was pulled in out of the reservoir. I checked the vacuumn line from the brake booster and it appeared dry, so is it reasonable to assume that the master cylinder leaked fluid into the booster – on the other side of the diaphragm from the vacuum line? I plan to replace the master cylinder. What, if anything, should I do about the brake fluid in the booster? (This is a 1995 Ford F150 w/4.9L)

[Author]

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