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Perhaps I’m not the most mechanically inclined person in the world but I do like to do my best to fix what’s broken before calling a mechanic. Usually, I can get the job done cheaper if not faster, than would otherwise be possible. Then again, sometimes things take a little worse turn.

About a week ago, my wife told me that her Passat had a check engine light on, a new occurrence for that car. It bugged me a little, but not enough to be overly worried. That evening when she got it home, I took a look and found the light still on. So, it wasn’t a case of a loose gas cap or something that simple. I started it up and did some looking/listening under the hood.

Gasoline engines run on a mixture of fuel and air balanced just right so that it burns inside the engine. There’s a sensor just behind the air filter called a Mass Air Flow sensor that keeps track of how much air the engine is pulling in so that the computer knows how much fuel needs to be fed into the cylinders. (Bare in mind that this is a gross oversimplification of the process.) Since gasoline engines need so much air they create a strong enough vacuum that it can be used to do other things on the car. You’d be amazed and just how many things are vacuum powered on your average vehicle. Everything from parts of the air-conditioner to the fuel pressure regulator have a tie in. Most of these vacuum powered devices are hooked into the system upstream of the MAF. When one of them springs a leak the computer detects that more air is reaching the cylinder than should be and tells you something is wrong with a nasty orange light on the dashboard. If you’re lucky, you can sometimes, not always, hear a distinct hissing sound in the engine compartment near where the leak is.

In my case, the hose feeding into the break vacuum booster went bad on me. I’ll have to get some shots of the old hose and add them here later. Here’s the new one installed with a replacement grommet:

Do you see that shiny new host there in the middle attached to the shiny new check-valve and the shiny new grommet/gasket that it’s seated into in the break vacuum booster? If that doesn’t mean much to you, the only “clean” hose a little to the right is the one that I’m talking about and the big black thing that it is hooked into is the booster. It doesn’t look like much but the booster puts extra power into the breaks when you’re stopping. Not something that you want to have fail!

A vacuum hose isn’t really anything that complex to replace, or at least that’s what I thought when I started this mess. Of course, the local Volkswagen house didn’t have the part in-stock and couldn’t identify it for certain either. The part’s manager was nice enough to order the two parts his diagrams said it could be, since he’d sold both of them in the past, and let me take the one I needed. That took a week to finally show up.

That Saturday, I spent a good two hours trying to get the other end of that hose out of the engine. It’s buried up under the back side of the engine where it is almost impossible to get to unless you’re all but hugging it. Once I finally figured that little bit out, it came off pretty easily and the new hose hooked up just fine. By this point I was probably running a little low on blood sugar as I hadn’t had breakfast yet and found myself having trouble with the check-valve end. So, as an experiment, I pulled the little grommet out of the break booster and put it on the check-valve thinking that I might be able to seat the valve more easily that way.

Nope.

Between trying to seat the valve and realizing that I would have to put the grommet back, I dropped it. As cars have a tendency to do, it ate the grommet. I’m still not sure where it landed though I did find it when I finally got the vehicle running again. After a good ten minutes of fruitlessly looking with a flashlight around the engine and under the car I gave up. Even in broad daylight there are enough nooks and crannies in the engine compartment to turn hunting for a lost something into cave exploration. So, I went looking for a replacement. No luck. Another call to the Volkswagen house and another order, they didn’t have the grommet in-stock but could order it, and I was stuck waiting until the following Tuesday.

The new grommet went in perfectly and I didn’t drop it! Yay! It also seemed like the check-valve went in a good deal easier with the new grommet as well. So, two plus weeks and the check engine light is gone with about forty dollars in parts. If you factor in my time, it was much more expensive than the about two hundred or so I would have paid a mechanic to do the job, but that’s the way things go! On the other hand, I can say I’ve replaced a vacuum booster check-valve which is a little unusual for your average author/computer programmer.

~ by Chris on .

Tags: car trouble