Fluid Leak Diagnosis at Johnny's Automotive
Oil, coolant, transmission fluid, or just AC water? We clean the area, trace the drip back to its actual source, and send you photos of what we found.
There's a spot under my car. How do I know what it is?
Color and location are a starting point, not an answer. Dark brown or black is usually engine oil. Bright green, orange, or pink with a sweet smell is coolant. Red or reddish brown and slippery is transmission fluid. Clear to amber, oily between your fingers, and near a wheel or the firewall points at brake fluid. Plain water dripping from the middle of the car on a hot afternoon is almost always AC condensate, which means the system is working the way it should and there is nothing to fix.
That narrows things down. It rarely tells us where the leak actually is. Fluids don't fall straight down. They run along the block, follow a seam in the pan, ride a wiring harness or a frame rail, and drip off the lowest point they reach, which can be a foot or more from where they got out. Airflow at highway speed carries them further back. The spot on your driveway is where the fluid finished, not where it started.
So we go find the start. First we clean the area, because old residue and road grime hide a fresh leak and make a small seep look like a catastrophe. Then, where it helps, we add a UV dye to the system in question and run the car the way you actually drive it. Under a black light, the dye traces back to the exact gasket, seal, line, or fitting the fluid is leaving from. On a leak that only shows up warm or under pressure, that is the difference between an answer and a guess.
You get photos of the source itself on your phone, plus an honest read on how urgent it is. Not everything that leaves a mark needs fixing today. A light seep at a valve cover that hasn't moved the oil level in months is a watch item, and we'll tell you that. A wet brake line is a different conversation, and we'll tell you that too.
Choose your shop
Problems we fix
Our experts diagnose and resolve any issue.
There's a spot where I park but the fluid level looks fine
Usually a slow seep that loses less than the dipstick can show, or a leak that only opens up once things are hot and under pressure. It is still worth identifying now, because what it turns into is a much bigger deal than what it is today.
Clear water dripping under the middle of the car in summer
That is almost always condensation off the AC evaporator draining out the way it was designed to, and it is more noticeable here than most places. If it is clear, odorless, and evaporates off the concrete, there is nothing to repair.
I smell something sweet after I shut it off but there's no puddle
Coolant hitting a hot surface turns to vapor before it ever reaches the ground, so the smell shows up long before a drip does. A pressure test holds the system while it's cold and gives the leak somewhere to show itself.
I keep adding oil and I've never seen it drip
Oil that leaves at speed gets blown backward and coats the underside of the car instead of pooling. Cleaning the area and putting dye in it separates that from oil the engine is actually burning, which looks identical on the dipstick.
Reddish drips near the front after a long drive
Transmission fluid and power steering fluid are both red and both live up front, so the color alone doesn't settle it. Where the trail starts does, and that is the part we chase rather than guess at.
It leaked for a week and then quit on its own
Leaks that stop usually mean the level dropped below the hole, or the seal is only letting go under pressure or at temperature. Neither one is fixed, and the second one tends to come back at the worst possible time.
More computer diagnostics services
Explore our other computer diagnostics services.
Check Engine Light
Check engine light on? We pinpoint the exact cause with advanced diagnostics and provide clear repair options — no guesswork.
Learn morePre-Purchase Inspection
Buying a used car? Our thorough multi-point inspection uncovers hidden problems so you can buy with confidence.
Learn moreVehicle Inspection
Vehicle Inspection evaluates relevant vehicle systems and documents findings for repair planning.
Learn moreFluid Leak Diagnosis questions, answered
Common questions about our fluid leak diagnosis services.
Can you tell what it is from a photo of my driveway?
We can usually narrow it to a family of fluid from the color, and that helps you decide how fast to come in. What a photo can't do is tell us where it came from, since the drip point and the source are often nowhere near each other. That part takes a lift and a light.
Is a small leak actually a problem?
It depends entirely on which fluid and where. A little weeping at an old gasket that has held its level for months is something to keep an eye on, not an emergency. Anything wet in the brake or fuel system gets treated differently, and we'll be clear about which one you have.
Does the UV dye hurt anything?
No. It is made for the system it goes into and stays in circulation with the fluid, so it doesn't change how anything works. The only catch is that it needs some run time to reach the leak, so on an intermittent one we may ask you to drive it and come back.
Why do I need to leave it if the leak is obvious?
Sometimes we don't, and if the source is right there we'll show you and move on. The cases that need time are the ones where everything underneath is already coated, since we have to clean it, run the car, and let the leak reappear on a clean surface before we can honestly say where it starts.
Do you have to take the car apart to find a leak?
Rarely. Most of the work is cleaning, lighting, and knowing where fluid travels on that particular engine. If we do reach a point where something has to come off to see the source, we'll tell you what and why before we touch it.
Request an Appointment
ASE Certified Technicians
ASE certified techs working on your vehicle
Flexible Drop-Off Hours
Convenient service options
20+ Years
Decades of trusted service