Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.
An oil leak can lead to high oil consumption, a waste of money, and serious engine damage when not caught in time. But trying to confirm or find the source of a leak can take you hours sometimes, especially with plastic covers bolted around engine and transmission components, plus road grime and oil covering the engine, transmission, and other components.
Sometimes, a leak problem may become self-evident because of the greasy or oily spots it leaves behind on your garage floor or driveway. But you'll find it difficult to detect a small or internal leak unless you regularly check fluid levels regularly and notice that a particular fluid or oil is gradually going down.
Either way, trying to find out where a leak is coming from may prove difficult at times without a good strategy. When you suspect an oil leak—or you're sure about it—and want to find the source, apply these practical steps at home to find out where that potential leak is coming from.
|Common Oil Leak Sources|
Deteriorating seals or gaskets
Broken or stripped bolts
Abnormal crankcase pressure
Bad installation of components
Preparing to Find the Oil Leak
First, you want to search for a leak on clean surfaces so that you can easily spot a greasy stain.
However, if oil, grease or dirt covers the surface of those components you suspect of leaking, get a degreaser from your local auto parts store and clean those surfaces to better trace the leak. Take your car to a car wash facility with a source of pressurized water, if necessary.
Spray degreaser all the way around components, hoses, brackets, oil pans and under the chassis. Following the manufacturer’s instructions and with the engine cold, power wash all the necessary components. Washing the engine when cold minimizes the chances of creating steam, which may lead to electrical faults.
Finding the Leak
With your engine or those suspected leaking components cleaned, now you need a starting point to begin your search. If you are suspecting a leak because of a few oil spots you’ve found on your garage floor, place some old newspapers under your car to help you better locate the oil source.
Do this the night before you plan to start your visual inspection, if necessary, to allow the dripping leak to leave its trace. However, keep in mind that some oil leaks will only occur during engine operation.
This will be your starting point in finding where the leak comes from. If you know you have a leak in a particular system because of low oil level--engine, transmission, steering or braking system--you already have an area to concentrate on.
When ready, raise the front of your car, secure it safely on jack stands and block the rear wheels with a couple of wooden blocks to prevent your car from rolling.
Note: Some people, especially professional car technicians, use dyes to find difficult to locate leaks. Watch the next video so you have an idea how they do it. You still can use this technique on your own car, but it's a little more expensive than the techniques we offer here.
Tracing the Leak
If you placed newspaper under your car, begin your visual inspection directly above the oil stain left on the paper; otherwise, start doing a general inspection on the suspected areas. Look for any traces of wet, shiny spots of oil around the system or components you suspect with a leak.
- Look for wet, darkened areas under the engine, transmission or steering system. Follow the wet area upwards to its highest point. See where the trace of oil leads.
- Pay special attention to gaskets and seals around those areas you suspect of leaking. They will cause problems as they wear out over time.
- Engine oil leak usually leaves behind clear, light brown (fairly new oil) or dark brown (used oil) spots behind. Depending on the location of the oil spot on the floor, look around the oil pan, the front and rear crankshaft seals, around the timing cover, and the area where the cylinder head and block come together (the seam) for a possible head gasket leak.
Also, if you recently changed the engine oil, there's a couple of things you want to look at: First, double check for a tight filter or that the gasket from the old oil filter wasn't left behind; otherwise it's going to leak. Use a mechanics mirror or any small mirror to inspect the mounting base of the filter, if necessary; then try to turn the filter counterclockwise with your hand to confirm it is tight.
Other common places for oil leaks are the oil drain plug, cylinder head gasket and valve covers around the top of the engine.
- If your vehicle has an automatic transmission with metal lines that connect to the oil cooler on the radiator, inspect those lines for damage, as well as the front and rear of the transmission for leaking seals, and the oil pan gasket under the transmission. Transmission oil in good condition has a reddish color. Old transmission oil has an opaque, dark brown color, and possibly smells burned. It's easier to detect when the oil drips on a newspaper or piece of cardboard placed on the floor under the transmission.
- A steering system leak will leave a clear, yellowish fluid on a piece of cardboard or newspaper. If you suspect a leak in the system, start the engine, engage the parking brake and block the wheels if necessary. Then have an assistant to turn the steering wheel slowly from side to side without hitting the stops at each end. Meanwhile, look around hoses, metal lines, the pinion shaft, pump and reservoir container. If there's a leak, system pressure probably will make it obvious. Frequently, a steering pump that squeals whenever you turn the steering wheel points to a fluid-starving system. So check the steering fluid level.
- Brake fluid is similar to steering fluid in color. If the fluid leaking has a light, yellowish color but the steering system has the correct amount of fluid, take the leak seriously and carefully look around the brake system. Check the brake master cylinder, follow the brake lines connected to it, each brake caliper and wheel cylinders.
Fixing the Leak
Once you have found the leaking source, you can decide whether this is something you can fix on your own. You can fix some leaks with little effort, even if you have little or no mechanical experience, for example, when replacing a damaged valve cover gasket on most vehicle models. Also, some products can successfully stop some small leaks. If you are mechanically inclined or have some auto repair experience, you may fix an oil pan leak with the help of your vehicle repair manual, depending on your particular vehicle make and model. Replacing a crankshaft or transmission seal, however, requires more skills and perhaps special tools and experience, depending on your particular make and model. Still, check the repair manual for your particular vehicle to see if this is something you can tackle on your own.
If you don't have the manual, buy an inexpensive aftermarket manual at your local auto parts store or online.
Usually, oil leak problems are not a concern on new or fairly new car models, but as the engine accumulates miles, components age and deteriorate, making leaks a common maintenance problem from time to time. So, learning how to find them may prove a valuable skill. Whether you can fix the problem yourself or need to have someone else do it for you, knowing the source of your car’s oil leak will help you make a better repair decision. And you still will save money and valuable time in the future.
Test Your Knowledge of Car Oil Leaks
For each question, choose the best answer. The answer key is below.
- An internal oil leak may cause what smoke color:
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
Question: How do I find automatic transmission oil leaks?
Answer: You may need to pressure wash the transmission and then trace the oil as it begins to leak. Usually, you'll find it around the pan gasket, front or rear gasket, or around the cooler lines.
Question: How can oil wind up in my coolant reservoir?
Answer: Usually this comes from a blown head gasket or leaking oil cooler inside the radiator tank. Oil leaks into coolant passages, circulates through the system and ends up in the reservoir. Test the engine compression to check for a blown gasket and have the transmission oil cooler checked.
Question: How do I know if the leak is coming from an engine or from a transmission filter?
Answer: Transmission fluid is red and has a smell like petroleum. After it's been leaking for some time, you'll notice a drop in the level.
Mr M Poynter on July 27, 2019:
Hello, after my Mot I was Advised I had a had an Oil leak, but it is not Excessive (8.4.1 (a)(i) they have put it down as amber condition and have advised I have a have a diagnostic test. I book in for a test with KWIK FIT who said a diagnostic won’t come up with anything but they were willing to have a look at my car for me, after leaving with them while I went for lunch I was told they thing it could be coming from the sump. I have an automatic Vauxhull Meriva it is a 63 plate. Can anyone advise me any further with this please.
Dan Ferrell (author) on July 27, 2017:
Excellent tip. Thanks for sharing.
AL LECOU on July 26, 2017:
Awesome articles on Vehicles.
I recently fixed a common problem on a 05 Nissan Titan. The oil cooler is a canister with coolant lines running to it. The oil filter attaches via a through bolt. Behind the canister is a gasket and over time it deteriorates and leaks. Nissan's solution is a $ 400 new part when you only need a $ 5 gasket and 22 mm deep socket.