Car repair experts: brakes - master cylinder leaking or just a spill?

[soupcxan]

Took DW's car (early 2000's Mazda w/ 115k miles) for state inspection and they said they couldn't pass it because the master cylinder was leaking. Opened it up at home and saw that brake fluid had eaten off the paint on the power booster (attached photo). However, the master cylinder was still full of fluid, and DW said it hasn't had any loss of power while braking. The car had the oil changed last month with one of the free inspections/fluid checks that they usually do and they didn't mention anything.

My question is, how definite is it that the master cylinder needs to be replaced? I'm thinking it's possible that they "topped up" my brake cylinder at the last oil change and spilled some, overfilled it, or didn't put the cap on tight enough, and this is what ate the paint. I couldn't find an active leak, but there seemed to me moisture around the cap. If the leak were coming from the back, it seems like the top of the plastic tank would've been dry. Can the dealership do some kind of pressure test on the tank's integrity or are they just going to say "oh you gotta replace that, $300 please"?

The second question is, now that the paint on the booster has been eaten, does it need to be repainted/replaced as well? We might keep this car another year or two at most so I'm not looking to make investments to keep driving it for 10 years.

Thanks for any advice.

 

[My Dream]

The dealer can do a pressure test on the brake system but as you metioned it is possible that the service center may have spilled some brake fluid onto the booster and maybe not wiped it clean, thus eating away at the paint. I would:

Check the seal around the mater cylinder and view whether\it has been damaged in anyway.
Monitor the fluid level in both partitions if it has them, some divide front and rear brakes should there be a leak in one system, the brakes will not totally fail.
Do a visual around the master cylinder to see whether there are any leaks, keep in mind it could be leaking inside the master thus the leak would go inside the booster.
Clean the booster with soap and water and repaint the area so that it doesn't set off a red flag next time you go to the State Inspection, if you catch my drift.

Refill the master if it's low.

Good luck and keep us posted.

 

[kumquat]

It's hard to say from a picture what the problem is. I'd make sure the cap is on tight, cover the breather in the cap (if there is one) and pressure wash everything in the general vicinity. Now watch for new leaks.

You don't have to repaint but it looks better. If you can get a rattle can in there, why not.

 

[Nords]

Clean the booster with soap and water and repaint the area so that it doesn't set off a red flag next time you go to the State Inspection, if you catch my drift.

I've never heard of failing a car inspection for that before. Holy cow, they could've had us any time they wanted us on any of our cars for at least the last 25 years.

If you're not seeing a trend in the level of the brake fluid reservoir, then I'd clean up the master cylinder and tell them your clumsy mechanic spilled some on your last brake job.

Sounds like the inspectors are leaning just a little too far forward in their zealous commitment to driver safety.

 

[Telly]

The seal in the rear of a master cylinder is lubricated with brake fluid, and over many years many miles it is common to see a loss of paint and a bit of rust on the vacuum booster due to the film of brake fluid. But only a trail downwards from the master to booster connection. It usually looks like a tall thin triangle with it's narrow base at the bottom edge of the booster.

But that does NOT describe your picture! I had to lighten up my monitor to see it... yours has paint crazed from the 9 O'clock position all the way to 3 O'clock. And the brake fluid residue extends above that too. It's a mess. And on a pipe or hose (I can't tell which from the pic) that routs under the master. There is a lot of brake fluid evidence there. Too much. I would say it looks recent, as there is a lot of paint bubbled off, but little rust yet.

But why? Well, without being able to look around it in person, I can only make a few guesses. I tend to doubt its weepage from the master's rear seal, as it is all over, unless that seal is leaking pretty badly.
Look at the rubber seals that the plastic reservoir presses into to seal it to the aluminum body of the master. Is one of those leaking, like the rearmost one?
What about the reservoir cap(s)? Are the cap seals hardened to stone?
Is there a small split or crack in the plastic reservoir? Even a crack on the top could allow fluid to slosh out when driving.

This is one of the many advantages to people who maintain their vehicles themselves... nobody to do something poor to their car, and leave them wondering. Long time DIY is also one of the foundation blocks that made my unexpected early-early retirement possible!

 

[landover]

Check the rear part of any slow leak, sometime it is difficult to spot brake fluid compared to engine oil. I am guessing this is a stick-shift car, small black tube on right going to clutch master cylinder. Anyway how can inspector determine that there is leak unless there is some sort of testing, and after you cleaned the area and assured that there is no leak, inspector needs to do some testing, not just visual inspection?

I had a recent slow leak in clutch circuit due to a loose fitting, I came to know only after the brake fluid indicator light came up, there was no visible fluid leak. I just turn the fitting and its not leaking anymore, atleast fluid level is not going down.

 

[Walt34]

As the others have noted it could be spilled fluid. I can't tell from the photo.

I'd clean it up a bit and take it to another inspector.

That said, if it really IS leaking I'd get that fixed immediately. Brakes and steering are things I do not defer maintenance on. The outcome is usually bad.

 

[Nords]

I'd clean it up a bit and take it to another inspector.

Around here you have to move fast, and I don't know if even that will work anymore.

Failed Hawaii inspections are written up as such and require a return visit to the place that failed you. (The second visit is "free" because you've already paid for the first visit.) Once the paperwork is in the database the state tracks your VIN and hypothetically the other inspection sites can't give you a do-over. This applies even if your tire tread is below minimum thickness. You could buy the tires at another inspection station but you still have to return to the original place to "clear" your failure in the database.

Enforcement is negligible unless you get pulled over for something else... and until you try to renew your registration.

We were failed once years ago because our Florida vehicle had a registration number of 17 digits, and Hawaii's database only had room for 14 digits. So our registration "didn't match" our state paperwork. Another station was notorious for determining that your headlights were out of alignment, requiring a $15 service. However it was also notoriously "flexible" on other inspection criteria so they had a rep for being the place to go if you were a little below standards.

 

[soupcxan]

I don't think the first place's inspection ever became official - I never paid nor received any paperwork. I took it to the dealer and they passed it without comment.