Take the 2-minute tour ×
Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. It's 100% free, no registration required.

The brake fluid reservoir level drops very fast in my 2007 4WD V6 Toyota Tacoma, probably within 3-5 days of filling it up. The funny thing is, it drops to just below where it says minimum but not further down, which makes me exclude the possibility of brake lines leaking somewhere downstream in the system and suspect that the problem is that the reservoir itself has a leak very near the top which causes this initial level drop. The brakes work fine but this causes the brake light to be on all the time.

I was wondering if replacing the reservoir will involve draining and bleeding out the whole system. Or can I just pump some out the top to below where the reservoir is mounted, replace and refill it?

EDIT: I noticed that the master cylinder fluid tank is mounted onto a drumlike device (what is this called?), which, I assume transitions and adapts the pedal motion to the cylinder. Does the liquid from the tank go into that drum as well? Because if it does, it could be that the drum is leaking somewhere.

share|improve this question
2  
Do you see any fluid leaking somewhere? That fluid need to go somewhere. Check where the brake pedal rod go through the firewall from inside the cab, if it's leaking from there it could be a master cylinder failure. Also, I've read that some brake fluid leaks to the booster, but it's pretty rare. –  Gabriel Mongeon Oct 21 '13 at 14:37
    
@GabrielMongeon, haven't observed leakage but I could try. But if it leaked where you say it might, wouldn't it keep dropping even below the minimum notch and not stop there? –  amphibient Oct 21 '13 at 14:39
1  
that seems a pretty odd behavior. The thing is that all that brake fluid have to go somewhere, once you find that you'll be able to better diagnose the issue. –  Gabriel Mongeon Oct 21 '13 at 14:58
3  
This may be silly but also check for stains on the floor after long parking periods. And I wouldn't completely discard a leakage down the line, since pressure in fluids increases the deeper you go, it COULD just be (though would be much of a coincidence) that the needed pressure to go through a crack down the system is found with oil above your minimum mark. –  PedroC88 Oct 22 '13 at 0:59
4  
Another possibility is that you just have a lot of air in the system (failure to properly bleed it). This happened to me - brakes were "mushy" and I kept "losing" fluid with no visible leak. Eventually, after enough top-offs, it stopped happening and the brakes got firm. –  R.. Oct 22 '13 at 3:08
show 3 more comments

1 Answer

As another pointed out, your master cylinder could be faulty. I had mine resleeved with stainless steel. Any brake & clutch specialists like repco can do this. To remove and replace is not complex.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.