Q & A #50 With The Auto Specialist
Q & A #50 With The Auto Specialist
Thanks for joining me for today’s installment of the Auto Specialist. Several weeks ago, I mentioned that I had driven past a few dealerships in my area and wasn’t surprised that the lots were empty. This was after the “Cash For Clunkers” deal had ended and a lot of folks expected sales of new vehicles to remain brisk. We now know that sales were destined to slump after the CFC deal had expired. That suggests there are millions of people driving older cars with components that will soon begin failing.
The goal of this column is to educate you about your car and the parts that are responsible for keeping it on the road. Eventually, you should be able to replace parts, such as your fuel pump, oil filter, and catalytic converter. You should also be able to troubleshoot minor problems with your engine and transmission. Today, we’re going to help Dennis understand what an engine leak down test is. We’re also going to help David with his Maxima’s battery. Let’s get started.
Question: I own a 2002 Ford Explorer with 89,000 miles. I took it to a local repair shop a couple of weeks ago to have them run a few tests. They said that my engine has a compression leak and that I should have a leak down test done. I told the mechanics to hold off for now. I’ve been through the archives of the Auto Specialist and can’t find anything about a leak down test. Could you explain what it is?
Answer: Thanks for writing, Dennis. An engine leak down test measures the loss of compression from your cylinders. All cylinders lose a little compression. But, if the loss climbs above 30%, your engine needs serious attention.
With the right tools, you can perform a leak down at home. Visit any auto supply store and pick up a leak down gauge. Then, remove your spark plugs and rotate your engine so that the target cylinder’s piston is at the top center of the combustion chamber. When it is, the intake and exhaust valves should be closed.
One end of the leak down gauge goes into the hole in which the cylinder’s spark plug rested. When you apply air pressure, the gauge will identify the percentage of compression leak. If the leak is significant, you’ll need to diagnose the root cause. That’s a matter of identifying where air is escaping. Hope that helps.
Question: I drive a 2000 Nissan Maxima and there’s 121,400 miles on it. Yesterday, I was stuck on the freeway because there had been an accident. I wasn’t involved in the accident, but it turned the freeway into a parking lot. Nobody could move an inch for over two hours. I kept my car on because it was cold and I wanted to listen to the radio. Eventually, my battery died. I got my car towed home and this morning a friend jump-started it for me. The battery seems fine. Did I do any damage to my car by letting it die like that?
Answer: Thank you for your question, David. In short, probably not. From what you have described, it sounds like you simply ran the battery down by keeping your car on without driving. Driving charges your battery. Now that your friend has provided a jump-start, it should be fine.
That wraps up another segment of the Auto Specialist. Thanks again to Dennis and David for sending in their questions. As always, we’ll have a new batch of car problems to help diagnose in the next installment. Until then, drive safely.
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Tags: Car Q & A, Car Q and A, Q and A
