Finding and Fixing Leaks

Identifying Fluid Types

If you’re reading this article, it’s likely you’ve seen a puddle or spot under your vehicle. The first question to ask is, “What fluid is that?” There are several types of fluids in your vehicle, most of which are colored to aid in their identification.

• Engine oil is usually brown or amber. The older it gets, the blacker it seems to turn. If you see a blackish fluid under your vehicle, it’s likely to be engine oil.
• Automatic transmission fluid is usually red. As it gets older, it can appear brown or a very dark brown, depending on how old it is.
• Manual transmission fluid can come in a variety of colors. I cover this topic more in the section on manual transmissions below.
• Coolant can also be a variety of colors these days. Traditionally, it’s been green, but we now have red, orange, yellow, and blue as possible coolant colors. I’ll talk more about this in the section on coolant leaks below.
• Power steering fluid is often a light amber, but some systems use automatic transmission fluid. It can be confusing if you have automatic transmission fluid in your power steering system. As with most leaks, you would need to put your eyes on the source to know its true origin.

No matter what fluid you find, you’ll likely have to go on a search to find where it’s coming from. Identifying the color of the fluid is only the first step, as it gives you an idea of where to start looking. For now, let’s start with engine oil.

Engine Oil

Engine oil usually appears either black if the oil is old, or a clear amber if the engine oil is new. Then there are a bunch of shades in between. Engine oil usually has a slippery feel when you rub it between your fingers. Sometimes it can have a distinctive odor, like old coffee. Most people know engine oil when they see it. If you’re in doubt, you could remove the dipstick from your engine and compare the fluid on the ground with what you see on the dipstick. If they match, it’s probably engine oil that’s leaking.

Engine oil normally leaks from the engine. However, it can leak from other places depending on the vehicle. Some vehicles use a separate cooler for the engine oil. If that’s the case, the oil might route to a different location away from the engine itself. Some oil filters are located away from the engine as well. If you have one of these systems, be sure to check the plumbing going to these external filters or coolers when looking for your engine oil leak.

Also, in the case of a turbo-charged vehicle, there are oil supply lines running to the turbo. I realize that the turbo is often located in the engine bay, but if you’re looking for a hard-to-find oil leak, it pays to know all the possible places that oil can leak from or into. If the seals go bad inside the turbo, oil can leak into it, where it will be burned. So if you have an oil leak you can’t find on a turbo-charged engine, be sure to include an inspection of the turbo. The turbo is one of those places oil can leak into and out of, so be sure to include it in your list of things to check when looking for oil leaks.

When searching for an oil leak, I start high and work my way down. Oil leaks travel, usually aided by gravity. You might be surprised at how far an oil leak will travel. I’ve seen oil leaks end up by the rear muffler. So if you discover your engine is leaking oil, start looking toward the top of the engine for the source. Valve covers in particular are known to leak from time to time. Since the leak is near the top of the engine, it will then travel along the outside of the engine on its way to the ground. This traveling can mask its true origin. So be sure to start high on the upper parts of the engine when looking for the source of your oil leak.

The PCV System and Oil Leaks

The PCV system is designed to vent and control the pressures inside the engine. Any time you have moving parts in an enclosed space, such as inside your engine, you need to vent the assembly. If you don’t, excessive pressure builds up inside the system. PCV stands for Positive Crankcase Ventilation; in the case of the automotive engine, the PCV system is used to vent the crank case and control emissions.

Before the days of the PCV system, they used to vent engine pressure to the atmosphere via an oil draft tube. A problem with the PCV system can cause pressure to build up inside the engine. This excess pressure can aggravate existing engine oil leaks, so if you have a lot of oil leaks on your engine, it’s worth checking the operation of your PCV system. Consult your service manual for the procedures necessary to inspect and repair the PCV system on your vehicle.

Finding Engine Oil Leaks

Leaking oil can trap dirt and debris, covering your engine with a black muck. This muck can mask other possible leaks along the way. This is the real challenge when it comes to dealing with leaks: finding the source. In many cases, it can be multiple sources. For that reason, it’s a good idea to clean as much of the engine as possible when looking for leaks. This way, you’ll expose any potential leak sources and make them easier to spot.

There are a few ways to do this, none of which are particularly environmentally friendly. The first is by using a pressure washer at a local car wash. This can cause other issues, so I suggest you proceed with caution if you decide to go this route. One of the main concerns is that you might force high-pressure water into some of the electrical components on the engine. Do what you can to stay away from the ignition system and any other sensitive electronics if you decide to clean your engine this way. I can’t tell you how many times I’ve had people come to me after washing their engine only to find it wouldn’t start when they were finished. So be warned and stay away from as many electrical components as you can to avoid this issue. I’ve heard of people putting plastic bags on their distributors and other sensitive electronics when washing an engine this way. It’s a step in the right direction.

In addition to pressure washing, there are also degreasers available. You spray these products on the dirty engine and then rinse them off with a garden hose. The same cautions apply here. Also, be sure to read the instructions of the product you’re using to make sure you use it properly.

Once the engine is clean, you’ll have a much easier time finding the source of the leak. You might try running the engine for a while after your cleaning. If the leak is big enough, just running the engine for a short time might reveal the source of the leak.

If that doesn’t work, you might consider one of two options. The first is installing dye into the oil. There are fluorescent dyes available that you can put into your engine. As the oil leaks out, it will also carry the dye. You then take an ultraviolet light and shine it on the engine. The ultraviolet light highlights the oil leaks, making them easier to find. This is a very effective method.

Another method is to spray leak detection powder on the suspected area of the leak. You clean the area first, dry it off, and then spray this leak detection powder over the suspected area. Once the spray dries, it turns a very pure white. When the oil leaks, it becomes very visible against the white background. This is a good method if you don’t have one of those special ultraviolet lights to use with the dye. It’s also less expensive as a result.

Either method will work to help you locate the source of the leak. FYI, leak detection spray is often just repackaged athlete’s foot spray. Yeah, no foolin’. So if you can’t find the spray at your local auto parts store, you might consider hitting up the drug store for a can of athlete’s foot spray.

Once you find the leak, you’re faced with the task of fixing it. This can be an easy O-ring replacement or it can involve removing the transmission to get to a leaking oil galley plug. That would be a worst case scenario, but it does happen. For now, we’ll just focus on finding the origins of that puddle on the ground. I’ll leave the repairs up to you.

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