What would be leaking underneath car in the center along cross member?

Brake fluid light came on and had to refill reservoir. I put cardboard under car and seen 3-4 separate spots of dark liquid in center of cardboard. No gas smell and no real smell at all. Can this be a brake line leak? In the video link I go from bottom of passenger lower arm (it is dry) then the leaking starts at the top lower arm bolt to the cross member and the leak goes to the drivers side top lower arm bolt to the cross member and the calipers ect. are dry like the passenger side.


2006 sonata 3.3 v6

Circumstantial evidence
Brake light comes on, fluid added because reservoir was low, some sort of fluid/oil dripping from under car…
It very well seems like a brake fluid leak, but coincidences sometimes lead one to chase a red herring.

The fluid feels oily and is not water?
You checked all fluid levels, cold, and brought them to full if necessary?

What I’d do, besides trying to examine everything by flashlight, mirror, and feel, is to drive carefully and continually monitor all fluid levels (coolant, transmission, clutch, power steering, brake, engine…) very frequently (each drive cycle). This leak could cause a problem in a very short amount of time (minutes, few miles).

An air conditioner failure can cause oil to leak, but you can’t pull a dipstick or visually check it.

If any fluids continue to drop then I’d rest assured that was my culprit system.

Use caution. Keep in mind that any minor leak can go major and with brake fluid it could be catastrophic and cause an out of control car.

Since it’s a 15 - 16 year-old car, leaks like this are not totally unexpected, especially if this car has operated where road salt is applied to roads in winter.

Take it to a mechanic or DIY, but be careful.
:palm_tree: :sunglasses: :palm_tree:

Tow this car to the nearest independant mechanic. I would not drive it knowing that the brake light came on.


I respectfully disagree with @common-sense-answer . The circumstantial evidence leans too far toward brake line leakage. If you don’t have safe jack stands I’d tow it to a repetuble shop.


Notice that I said "What I’d do." I’ve had this situation before and when in my northern location, live in a very rural area with no traffic and 1 or 2 stop signs in 20 miles, literally.

Notice that I said…

I said…

Disagree all you’d like. I’m not sure what you’re disagreeing with, though.

You are welcome to your opinions. I have always been cautious in situations of this nature, racing motorcycles (road and dirt), dune-buggies, flying airplanes, driving old rusty cars, tractors, boats, etcetera, with or without brake problems, never having an accident after 72 birthday candles. A man has to know what he’s looking at, car mechanicals wise, live or drive in a rural area, and know his abilities and limitations, and have plans B and C. It’s not for novices or wimps and I thought I covered in my advice that in the wrong hands could be “catastrophic” (As in “Oh, the humanity!”). Whatever. :wink:

Plus this will rock you, but people here in Florida don’t where any masks, any more! We’ve moved beyond that annoyance. :astonished:
:palm_tree: :sunglasses: :palm_tree:

I simply disagree with driving a car on the roads after finding a near empty brake fluid reservoir combined with a puddle of anything on the ground. If that is what you would do, that’s your choice. I’ve made that choice before and expreriance has taught me to never take brakes for granted. So what I personally would do is safely put the car on jack stands and with reservoir, full have someone press on the brake pedal. Then I would search for brake fluid leaks. Then I’d try it with engine running. I’d take note if the pedal went to the floor at any time. A brake line leak if present should now be obvious. If not and the brake pedal goes to the floor there may be a leak in one of the cylinders and brake failure can still happen. But until I have diagnosed the brakes are fully functional, the car has no business on the road. If someone is unable to make a reliable diagnosis on brakes under the OPs observation I would recommend them to tow it to a shop. I realize as mechanics some controlled risks are warranted, but one should never advize driving car with potential brake problems. Yes here in Michigan we are locked down and my state is run by idiots, but we also have a lot of salt rusting brake lines. MANY times the rust causes pin holes that make brakes work minimally until the weakened hole explodes into sudden brake failure. Again it was a respectful disagreement. :hugs:

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You already know that “something” is leaking, that the brake fluid is “disappearing” and that there’s no reason to assume that the brake fluid won’t continue to “disappear”.

So would you rather slowly and carefully drive to a mechanic now or wait until the light comes on again and pay $300 for a tow?


Forgive my comments but I just can’t believe some of the answers. Ya think towing is safe? Ever checked some of the towing rigs/drivers out there and would rather tow than drive a few miles carefully to the shop? Brake fluid has a distinctive smell to it. You can’t mistake it for oil or coolant or trans fluid or PS fluid. You had to fill it up so smell the bottle and dip your finger in the leaked fluid and smell it. Elementary my dear Watson. After you have quickly determined it is brake fluid take it to the shop-you aren’t going to fix it yourself so what difference does it make where it is coming from?

My Morris Minor leaked brake fluid the whole time I had it. I would carry a bottle with me to fill up the master when needed. Sure anything can happen anytime, but tow it? I drove my old station Buick station wagon with the master going out in heavy traffic to get it home to repair. Pump the brakes and pedal to the floor. Keep a distance and be prepared for a quick stop. Yes I wouldn’t recommend rush hour freeway traffic with bad brakes but towing 50 miles was not in the cards. Just saying common sense and a little caution goes a long way.

Found the brake line diagram and looks to be the same area in the rear where the leaking is. There is nothing else in that rear area that could leak besides gas, right? I can’t see how coolant, power steering fluid, motor oil or gear oil is back there? No ac vents in back seat.

Can someone explain the colored circles I added in the brake line diagram? Red would be from brake booster and go to rear brakes (same line with purple). Yellow, blue and green would be parking brake going to shoes?

Green circle - parking brake handle
Blue circle - parking brake cable and attachment point
Yellow circle - parking brake cable and attachment point
Red circle - brake line and attachment point
Purple circle- brake line and attachment point


I would fill the reservoir, get in the car and hold the brake pedal down hard for 3 minutes, and see if the pedal sinks. Repeat with the engine running. Then re-check the reservoir.
If there is anything amiss, tow it…unless your mechanic is two miles away and you can drive at 10 mph and have a handbrake that works. Let the mechanics find the exact leak.
If nothing is amiss, I would also be suspicious of the fuel fill tube. It looks like something has melted the undercoat.


Brake fluid will take the paint off a vehicle, undercoating, too.
:palm_tree: :sunglasses: :palm_tree:

I think @common-sense-answer is right. About the evidence, not about the COVID junk that we shouldn’t be talking about anyway.

It is circumstantial. If the pads get worn down enough, that can trip the brake light until you add fluid, because the reduced thickness on the pads causes a fluid level drop systemwide.

So OP could have an actual leak of some sort of fluid, and need brake pads.


Getting back to the question at hand, low brake fluid does NOT mean there is a leak. As your brake pads wear down, the caliper cylinders have to fill up with brake fluid to keep the pads tight to the rotors. The FIRST thing to check when you get a brake light on the dash is the pad thickness of all disc brake pads. Most of the time you see this light, the pads are worn down.

This does not mean that you don’t need to get your brake lines inspected. They should be inspected every time you get a brake job, along with other stuff besides the pads. If you are in question about the lines, then the answer is yes to an inspection, an “eyes on” inspection, not opinions over the internet.

I see a few drops of whatever is leaking forming on a couple of bushings. Use a Q-tip to get some of that liquid and stick it in water. If it floats, it is oil based. If it mixes in with the water, it could be brake fluid or antifreeze.

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From my DIY auto repair/maintenance history, my experience working at car dealers, and my experience working in aviation, I am forever cognizant of “red herrings” when diagnosing leaks and take nothing for granted.

Fluid from leaks can run down (gravity), run across frame/suspension members, and get blown back from relative air movement while a vehicle is driven at speed. Finding evidence of 3 or 4 separate spots of fluid on the ground helps illustrate this.

Just saying, proper diagnosis is king. One of the last things I would like is to fix something not broken (ready, fire, aim) and miss fixing the actual problem. Leaks can be tricky and sometimes cleaning everything off and starting observation over is prudent. Most of know that chemicals are sometimes added to systems that allow using ultraviolet(?) lighting to illuminate leaks and locate the source(s).

I’ve had transmission cooler lines, fuel lines, brake lines, and power steering lines leak, eaten alive, after years of exposure to road salt, back when I drove in that Shxx (I’m so glad I am never doing that, again!). Often those leaks take some time and investigation to positively I.D. Just saying…

Oh, and I sometimes create my own leak mysteries. Besides air conditioner condensate puddles, I have an open-air vent near the cap on the coolant reservoir of my faithful 26 model-year old daily driver Dodge Caravan. Slowly, some coolant is lost to evaporation. I keep it topped off, but I must be very careful adding coolant so as not to have some fluid hit that top vent and puddle under the vehicle. There’s nothing wrong with it, it’s just designed that way. I’ve been shot by that false alarm a couple times when I walk out and see a puddle of coolant (good memory, just real short!). :face_with_hand_over_mouth:.
:palm_tree: :sunglasses: :palm_tree:

Apologies for being out of the forum yesterday. Please don’t bring this back to Covid. And I’m going to go back and delete the covid stuff to the best of my ability to keep the content that is relevant. Thank you.


This string started out well enough but then took a turn into crazy town before coming back. The low brake reservoir is circumstantial and does not prove a brake leak. In that location on a car it can be almost any fluid leaking. Don’t guess. If you have the wherewithal to fix this, jack it up and eyeball the source of the leak. If you don’t, does the brake pedal sink when you step on it with the engine running? If so, don’t drive it and get it towed to your shop. If the pedal feels firm personally I’d drive it to a shop as long as it was close and I could drive the route slowly.

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That’s par for the course around here, haven’t you ever listened to the show??


That far away from the engine? I don’t think so. This is simple - if it could be a brake leak, get it checked ASAP.


Well there are trigger words like “sunshine” that set people off and down the path. Really though how many times can you say the same thing about a brake fluid leak without someone saying something more interesting?

So can’t figure out what it is? Can’t smell it? Can’t see where it’s coming from? Brake fluid empty so that’s a good guess. Can’t or won’t fix it yourself? So drive to a shop or if you are fearful, tow it. When it is fixed pay the bill. How many times can the same thing be said?