Check for intake vacuum leak
Sometimes a vacuum leak will whistle or hiss and make itself obvious. But oftentimes, a vacuum leak will disguise itself as an ignition or fuel problem that defies diagnosis. Either way, an engine vacuum leak is bad news because allows "unmetered" air to enter the engine and upset the air/fuel ratio.
A faster technique for finding intake manifold vacuum leaks is to get a bottle of propane and attach a length of rubber hose to the gas valve. Open the valve so you have a steady flow of gas. Then hold the hose near suspected leak points while the engine is idling. If there is a leak, propane will be siphoned in through the leak. The resulting "correction" in the engine's air/fuel ratio should cause a noticeable change in idle speed and/or smoothness.
Aerosol carburetor cleaner can also be used the same way.
You may also have leaky freeze plug under the throttle body, causing the coolant to leak.
There are several ways to repair a leaky freeze plug.
One is to clean the surface of the plug, then sand it lightly with sandpaper, and pack it solid with a high temperature two-part epoxy such as gas tank sealer. Let it cure overnight. This trick usually seals leaky expansion plugs that would otherwise be very difficult to replace.
Another is to use a hammer and drift to knock out the old plug. Pounding in on one side of the plug will usually cause it to twist. The plug can then be pried out with a large screwdriver. Clean the hole, then apply a liberal coating of sealer to the hole and carefully drive in a new replacement plug. The plug must go in straight or it may not seal. Another option is to install a repair plug that has an expandable rubber grommet to seal the hole. You simply place the plug in the hole and tighten the bolt until it seals tight.
Monday, February 22nd, 2010 AT 11:54 PM