RAY MAGLIOZZI

Dear Car Talk: I have this hose with a right-angle bend that’s coming from behind the battery of our 1998 Mercury Mystique.

With it not connected, you have to really press down very hard on the brakes to get the car to stop. But I cannot find where it goes.

Any idea what it should be connected to? — Ernest

That’s the hose for your vacuum power brake booster, Ernest. And with it disconnected, you’ll not only lose your power brakes, but you should also have a massive vacuum leak.

This is confusing. A vacuum leak of that magnitude would make the car run terribly. If it ran at all. If you open the hood with that hose disconnected, the engine should be shaking like a wet dog. And you’d hear a loud sucking sound coming from the end of that hose. If you don’t, there’s a piece of information missing here.

One possibility is that someone disconnected the hose on purpose and then plugged it to fix the resulting vacuum leak. That would disable the power brakes but would allow the engine to otherwise run normally.

Why would someone do that? Well, let’s say they were selling the car to a guy named Ernest, Ernest. And let’s say the power brake booster failed. That would create a vacuum leak and would make the car undriveable.

Let’s say this same person didn’t want to spend $400 to replace the bad power brake booster. Well, they could unplug the hose and cap the resulting hole in the manifold. That would allow the engine to run, and maybe allow him to sell the car. “It runs great, the brakes are just a little hard.”

So, here’s what you can do, Ernest. One end of that hose attaches to the intake manifold. The other end attaches to the power brake booster, which is right behind the brake master cylinder. The master cylinder is the thing with the brake fluid reservoir.

If you remove whatever cap or plug has been put on there and reconnect that hose to the booster and the manifold, the power brakes should return. If nothing changes, or the car runs terribly, someone plugged up that hose to cover up a bad booster. That means you need a power brake booster.

The good news is that when you have the new booster installed, I’m sure they’ll plug that hose into the right place for you.

Got a question about cars? Write to Ray in care of King Features, 300 W. 57th St., 41st Floor, New York, NY 10019, or email by visiting the Car Talk website at www.cartalk.com.