Quick answer: The color usually tells you the fluid. Green, orange, pink, yellow or blue and faintly sweet is coolant. Light brown to black and oily is engine oil. Red or pink and thin is transmission or power steering fluid. Clear, odorless water after running the AC is normal condensation. If it smells like gasoline, or it’s brake fluid, don’t drive it.
A puddle is one of the few car problems that identifies itself before anyone opens the hood. Two things tell you almost everything: what color it is and where under the car it sits. Work through those and you’ll know whether you’re looking at something urgent, something to schedule, or something that isn’t a problem at all.
Is clear water under my car normal?
If the puddle is clear, thin, odorless water, sitting under the middle of the car toward the passenger side, and it showed up on a warm day after you’d been running the air conditioning, that’s condensation off the AC evaporator draining exactly where it’s designed to. It’s completely normal and needs no repair. A car parked after a hot drive can drop a surprising amount of it.
We’d rather tell you that up front than have you book a diagnosis for weather. Everything below is about the fluids that actually matter.
What color is the fluid leaking from my car?
Put a piece of clean cardboard under the car overnight. It gives you the color cleanly against a pale background, and it shows you where the drip lands.
- Green, orange, pink, yellow or blue, slippery and faintly sweet-smelling: coolant. The color varies by manufacturer, so judge it by feel and smell rather than by shade. It usually comes from the radiator, a hose, the water pump, or the heater core. Start at engine cooling system repair.
- Light brown to nearly black, slick and oily: engine oil. Fresh oil is amber; it darkens with miles. Usually a valve cover gasket, an oil pan gasket, or the drain plug and filter. See engine repair, or if it’s just weeping, we’ll catch it at your next oil change.
- Red or pink, thin and oily: transmission fluid or power steering fluid; both are commonly red, and telling them apart is about position rather than color. Transmission fluid ages to brown. See transmission fluid service or power steering repair.
- Clear to light amber, oily, slippery, and near a wheel or under the pedals: brake fluid. Treat this as urgent. It’s the one leak that can take your brakes with it. Go to brake repair, and read the “which leaks are safe to drive with” section below before you drive it.
- Dark, thick, and strongly sulfurous: gear oil from a differential or axle. Distinctive smell, hard to mistake once you’ve met it. See differential service or axle repair.
- Smells like gasoline and evaporates: a fuel leak. Stop driving it. Fuel near a hot exhaust is a fire risk, and this is the one case where we’d rather you didn’t drive to us. See fuel system service.
What does the spot under the car tell you?
- Front and center, under the engine: oil, coolant, or power steering. The busiest area under any car.
- Front, slightly to one side: often transmission, especially on front-wheel-drive cars where it sits beside the engine.
- Behind a front wheel, or inside on the driver’s floor: brake fluid, from a caliper, a hose, or the master cylinder.
- Under the middle or rear: differential, axle, fuel tank, or exhaust condensation.
- Inside the car, in the passenger footwell, smelling sweet: that’s a heater core leaking coolant into the cabin, and it usually fogs the windshield with an oily film too.
One caution on position: fluid runs along the underside of a car before it drops, and airflow pushes it backward while you drive. Where it lands is where the trail ends, not where it starts. That’s why finding the actual source usually means getting the car up on a lift and following it uphill.
Can a clutch leak brake fluid?
Yes, on a manual car. Hydraulic clutches use brake fluid, so a leaking clutch slave cylinder or master cylinder puts brake fluid on the ground near the bellhousing, or a damp patch on the carpet under the clutch pedal. Most leak guides will tell you that’s a brake problem. Often it isn’t, and the tell is the pedal: if the clutch has gone soft or the car has started grinding going into gear, the fluid is leaving the clutch circuit. That’s hydraulic clutch repair, and it’s the work this shop has been doing longest.
Which leaks are safe to drive with?
- Fuel: don’t drive it at all. Have it towed. If you’ve had service with us in the past year, your roadside coverage handles that: 24/7 at 866-588-0728.
- Brake fluid: don’t drive it. Brake systems are hydraulic; they don’t degrade gracefully when the fluid leaves. If the pedal has gone soft or sinks toward the floor, that’s confirmation rather than a maybe. See soft brake pedal.
- Coolant: short trips only, and watch the gauge. A car losing coolant is a car heading toward overheating, and overheating is what turns an inexpensive repair into a head gasket. See car overheating. Never open a hot radiator cap.
- Oil: check the dipstick before you go anywhere. A slow seep can wait for your next visit; a puddle that reappears overnight means you’re losing it faster than the engine can spare.
- Transmission, power steering, gear oil: schedule it soon. Not usually an emergency, but all three feed components that get expensive once they’ve run dry.
What happens at the free leak check?
The visual check is free. We’ll put it on a lift, look at where the fluid actually starts rather than where it lands, check levels, and tell you what’s leaking and roughly how bad it is. For a lot of leaks that answers it in one look.
When it doesn’t, because the leak is slow, only appears when the engine is hot, or involves two fluids at once, that’s real diagnostic time and it’s billable. We’ll tell you what it costs and get your approval first. Depending on the fluid that can mean a pressure test, a dye test with the car driven and then re-inspected under ultraviolet light, or cleaning an area down so we can see which seam it reappears from. Whatever we find is documented through our Digital Vehicle Inspection with photos, so you’re deciding from the same evidence we are. Loaner cars are also available at no cost if the testing keeps your car.
The most useful thing you can bring us is the cardboard. Color, position, and how much appeared overnight will often get us most of the way there before the car goes up on the lift.
Is the repair covered by a warranty?
Qualifying repairs at MotorCar Doctors are covered by a 36-month / 36,000-mile nationwide warranty on parts and labor, honored at participating shops across the country. A few items carry their own terms. Full details are on our warranty page.
Bring It In
We’ve been chasing leaks to their source in Beaverton since 1995, with ASE-certified technicians, for drivers across Aloha, Tigard, Hillsboro, Cedar Hills and the rest of Washington County.
Find us at MotorCar Doctors Auto Repair, 13203 SW Canyon Rd, Ste C, Beaverton, Oregon 97005, open Monday through Friday, 8:00 AM to 5:00 PM. Call 503-626-4810, and tell us the color and roughly where it’s landing. That’s half the diagnosis before the car arrives.