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On The Road

Getting to the bottom of that leak


My dog Ronin was elated to see Pixel – she’s one of his favorite canine friends – show up at the shop on a recent morning. But Pixel’s owner, Barbara, wasn’t so happy.

Ronin wagged his tail in anticipation of getting to play with Pixel as I asked Barbara what was wrong with her car.

The following is my interpretation of what may have been going through Ronin’s mind from there.

“Matt, please let me out so that I can play with Pixel! Hey, why do you need to get her mileage? Wait, why does she keep talking about a leak? I thought Barbara came to let me play with Pixel?

“Oh, great! Matt is headed outside to check on some leak in Barbara’s car, so I can make a mad dash to party with Pixel.

“Pixel said she missed her morning walk today because Barbara brought her here instead. Barbara said the car is leaking some dark-looking fluid onto the garage floor that smells a little like rubber.

“That’s too bad about the walk, but at least Pixel can play with me while Matt explains to Barbara what’s wrong with her car.

“Matt knows a lot about leaks, including the following.”

Long list of leaks

The list of potential leaks in a vehicle is virtually endless. Leaks are a common complaint for many drivers. They can come in every shape, smell and viscosity. Some leaks are more seep-like, in which case it could take thousands of miles before the owner even realizes something is wrong. Other leaks present themselves quickly with a physical drip.

What typically leaks in an automobile? Engine oil, transmission fluid, power-steerage fluid, the fuel system, the cooling system, the A/C system, hybrid inverter cooling systems, electric battery cooling systems and pretty much any system on the vehicle that contains gas or other fluids.

The most common leaks come from the engine and include valve-cover gaskets, cam seals, crank seals and sensor seals, or from the cooling system and include radiator hoses, the radiator itself, water pumps, the thermostat and the expansion tank.

A quick diagnosis

Coolant leaks tend to be more dramatic and usually include large fluid and/or steam loss. The low-coolant light should turn on, and you can physically tell that your car is overheating by hearing a hissing sound, smelling a sweet water odor or seeing steam pour out of the engine.

Cooling system leaks are not all dramatic, however. Some coolant leaks are stealthier in nature. These tend to be internal cooling system leaks, such as head gaskets, a cracked head or a cracked block. These problems are more difficult to diagnose. At my shop, we start off with a cooling-system pressure test and move on from there.

Engine oil leaks tend to be much slower, as oil is thicker than water and thus does not move as quickly. If a car has a serious oil leak, we will usually have to do some major cleaning, as the oil coats the engine itself. We have found that if we see oil spilled throughout the entire engine compartment, the engine probably has more than one leak. By cleaning the surface of the engine, you can attempt to determine if there is more than one leak. The best approach at that point is to start at the top (surface) of the engine and work your way down.

Regardless of the type of leak, it is always best to address it early. The longer you wait, the worse the leak can get, and you’ll probably have more damage to repair. As for practical maintenance, always consult the owner’s manual and make sure to check your fluids on a regular basis.

Back to the all important narrator of this column: “So, Ronin, it looks like Barbara’s valve-cover gaskets are leaking,” I said. “The oil is dripping onto the exhaust system, and that is why she is smelling the burning smell at the end of a long trip.”

Ronin’s reply: “It was nice of Matt to explain that to me, but I don’t really care – I’m a dog. I just want to know when Pixel is coming to play with me again.”

Matt Pataky owns Sunnyvale Foreign Car Service, 83 Pioneer Way, Mountain View. For more information, call 960-6988, email This email address is being protected from spambots. You need JavaScript enabled to view it. or visit sfcarservices.com.

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