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Don't top off brake fluid?

I took my car into a nation-wide car shop for its 30,000 mile maintenance (can’t take it to the dealer, as the dealership folded 3 yrs ago). It was noted that the brake fluid was low when I got the car back. I asked why it had not been topped off, & the mechanic said that low brake fluid is an indicator of brake wear & that I should wait until the brake light comes on, then bring it back to the shop to have the brakes replaced. Is this fact or fiction???

Depends on how much it’s down. But yes…as the pads wear down the fluid will drop a little. But I wouldn’t use the brake light indicator to tell me when I need new brakes. There’s probably a fill-to line and a add-line on the brake reservoir. Just make sure the fluid doesn’t go below the add-to line.

Mostly fiction… Waiting for the brake light to come on is NOT a reliable method a gauging brake wear…

I would learn how to check and top off all the fluids in my car myself…I would also learn how to remove a wheel and inspect my brakes myself. Otherwise, you are a duck in a shooting gallery…

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Personally, I would avoid this place in the future.

Assuming you have a Saturn or Pontiac? Find a good independent GM mechanic or GM dealer. Nationwide chains are the greatest source of complaints on this board by far when it comes to unnecessary and/or botched service and repairs.

Agree with the others. It’s fine to top off the fluid. Just be sure to suck a little fluid out when you go to change the pads if the fluid is full (you can always replace it if need be), otherwise some might spill over the top of the reservoir, and if it hits anything painted, will strip the paint.

It wouldn’t surprise me if the shop uses small bottles of fluid and didn’t want to crack open a bottle just for a little topoff - brake fluid absorbs moisture, so once you open the bottle you’re supposed to use it in short order.

Falling brake fluid is a normal condition as the brake pads wear and more fluid is needed to fill the caliper space. Adding too much fluid would require removing some when the pads are replaced again. I wouldn’t wait until the light came on though. There are minimum and maximum indicators for brake fluid and the fluid should be maintened between the two of them. I don’t think I would condemn the shop though without knowing how low it was and how soon the pads would need to be replaced. Good shops are getting harder and harder to find and I wouldn’t just fire one for something like this.

Your shop’s theory is rational, and it isn’t the first time I’ve heard it stated…but I recommend against it. I’d rather keep the fluid in the master cylinder and check the brakes routinely, perhaps every few times I change the oil. It’s entirely possible to have a brake problem that causes uneven pad wear and never know it if you’re only relying on the fluid level light.

During a tire rotation, most shops will inspect the pads and let you know the thickness of them. It’s an easy thing to do, and I suspect every mechanic commenting above this post does it instinctively. I do, and it takes just seconds. If they’re getting close, I know I need to replace them soon, and that gives me 5000 more miles to stop by a shop and get new pads so I can replace them at the next rotation.

But, levels must be maintained. oil, coolant, brake fluid, steering fluid…they’re all important, and there for a reason.

An indicator that the brake pads are worn is to look at them…otherwise, keep all fluid levels to recommended levels. This is especially important with brakes IMO, as I feel any brake fluid you add decreases the moisture percentage in the system and may raise the “wet” boiling temperature.

Your shop is absolutely right on this one. Leave it alone, but do check the fluid from time to time, when it gets to the minimum, then have the pads inspected/replaced.

When you have the pads replaced, have the brake fluid flushed at that time so that you start off with new pads and new brake fluid each time. That will take care of the moisture build up problem.

BTW,even when the brake fluid hits the min mark, there is still plenty of brake fluid in the system to keep the brakes working. This is only the reservoir where excess fluid is stored and drawn from as needed to compensate for wear or leaks.

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I disagree with keith on this one…Brake fluid level in the master cylinder is NOT an accurate gauge of brake pad wear…Brake wear can only be determined by inspecting the brakes…Why wait until a red warning light comes on to top off the fluid level?? The shop you went to, if you go back there with the warning light on, I GUARANTY you they will tell you you need to replace the brakes…They have turned that fluid warning light into a cash cow…

While it is true that the fluid level drops as the disc pads (not the shoes on drum brakes) wear, it is not an accurate gauge. As the pads wear, the caliper piston comes out to keep the pads close to the rotor, therefore, the fluid level drops. This is one of the benefits of disc brakes, they self adjust.


Let me clear something up. I did not mean that all the other advice about checking the pad life was wrong or unnecessary or bad advice. I do believe that it is good advice, but the fluid level in the master cylinder is a very good indicator of the pad life left. There is no advantage to topping off the fluid.

As the fluid gets close to the min line, then is is very important to get the pads checked. I would not wait for the brake light to come on. Checking the pad life is not as easy for everyone as it is for some here. In many cases,it involves pulling off the front wheels and some people here have to pay someone else to do that. Even though it is easy, it does take up significant shop time, lift time and mechanics time. Not everyone has spoked alloy wheels that they can just look through.

If the OP tops off the brake fluid, then they loose that indicator of brake life, and there is nothing to be gained by topping off the fluid. In other words, everything to lose, nothing to gain.

I will add that if you have 4 wheel disc brakes, you need to have the pad life checked on all four when the fluid level is about half way between the min and max lines. Use this information to determine the relative wear rate between the front pads and the rear pads to get an idea of when the brake pads will need to be replaced.

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When I have opened master cylinders and found the fluid dark, murky and at the bottom it has been my opinion that the maintenance has been lacking for quite a long time.

I always keep my brake fluid topped off. I’ve driven enough over the years to know the approximate mileage I can get out of a set of brake pad/shoes, but I still check them occasionally. If the master cylinder continues to get low on fluid on a regular basis I also know to look for signs of leaks in the wheel cylinders, calipers and brake lines.

Rod, that is why I recommend a brake fluid flush when the pads are replaced.

My Matrix has a relatively huge brake fluid reservoir which also serves the clutch.
I would never count on brake fluid level to be in sync with pad wear: too many variables.
I just take a peek at the pads when I rotate the tires.

No there is logic in this methodology…however I don’t wait for the brake light…I top it off… Just remember to use a squeeze bulb to suck some out B4 you replace the worn out pads Otherwise the fluid will overflow out of the Master Cyl when you push the caliper pistons back in… Not a big deal…but it CAN BE…if you get that NASTY SHITE on your PAINT somehow…You wont be happy about that I promise you.

Keth…I have to disagree about toping brake fluid off, especially if it is low as indicated to OP. I believe fresh fluid raises the wet boiling point, assuming there is already some moisture in the system and, if there is a leak, it does give you a little more buffer which may be critical. In the military medical clinic and the police department I worked, it was normal maintenance practice with ambulances, trucks and cars. To each his own, you have good reasons for not, these two organizations had theirs too.

Just using the brake fluid to check pads without doing it visually AND checking the system when it is low for other causes .is a really dumb idea on the part of the mechanic…he must have a bad back.

dagosa, I guess it depends on what “low” was. If it was near the min mark, I would expect that the maintenance man would have recommended that the brake pads get replaced, or at least inspected. But I do not agree with topping it off.

As for wet boiling point, brake fluid is not circulated through the system, so adding fresh fluid to the reservoir will not help the “working” brake fluid that is in the system. There is just no need to do it. Topping off brake fluid is so 1950’s.