Tips on Auto Vacuum Leaks

Engines are essentially self-sustaining air pumps, and they'll pump their chosen medium by whatever means they can. This means that air will flow through whatever hole it can, including, but obviously not limited to the main air intake. An engine may use dozens of vacuum lines to power any number of ancillary systems, and each line juncture is a potential leak.

Suspect Areas

Vacuum leaks almost always happen where the vacuum lines connect to either the intake manifold, accessory or any junction in between. Rubber hardens and shrinks as it ages, pulling away from the metal or plastic nipple and allowing air to enter in the gap. Under constant movement, vibration and heat, the hard rubber lines may also crack and split, allowing the ends to expand and leak even worse. Finally, the line will disintegrate so far that it may completely fall off the nipple.

Finding the Leak

One of the oldest and most reliable leak detection methods involves a can of ether starting fluid -- available at any department or auto parts store -- and some common sense. If you suspect a leak, simply spray the juncture with a one-second burst of starting fluid and listen for a brief rise in engine rpm. Bear in mind, though, that there is a bit of risk involved here; starting fluid by nature has a low auto-ignition point. Perform this procedure when the engine is cold, and stop when the exhaust manifolds get too hot to touch.

Splicing and Fixing

The simplest way to fix a vacuum leak is to cut the hardened line section off of the tube's tip and plug it back into the vacuum nipple. If the line won't reach after cutting, then you'll need a new one. If that section of tubing is preformed into a specific shape, then replace it with a slightly longer piece of universal tubing to prevent kinking. If it's an emergency, you don't have the money or can't find new tubing right away, then unplug the vacuum tube, wrap the nipple with some electrical tape to increase its diameter and reinstall the line.

Prevention

If you find one vacuum leak, then odds are that there are more on the way. A bit of tire conditioner can keep the rubber tips pliant, helping to prevent shrinkage and cracking. Fill a coffee cup with a non-silicone based tire conditioner, unplug the vacuum line and dip the tip of your line into it. Point the line downward, place an old rag underneath it and squeeze the line to remove any excess conditioner from the inside. Allow a minute for the conditioner to soak in and reinstall the line; finish the job by wrapping that conditioner-soaked rag around your line and conditioning the rest of it.