Monday, September 17, 2007


Intake Manifolds perform a very basic function. Simply put, it's job is to take the air as it enters the engine and direct it through intake passages into the runner ports located in the cylinder heads. Air entering the cylinders is mixed with fuel and power is produces from the combustion process. Intake manifold design greatly influences the performance of the engine throughout it's operation range.

One of the keys to making power in an internal combustion engine is to increase the flow and speed of air entering the engine. This can be accomplished several ways. One is to force the air into the engine by mechanical means such as a supercharger or a turbocharger. Both of these mechanical devices compact the air molecules, providing a denser oxygen charge and thereby producing more power. Air is also drawn in as the pistons descend in the cylinders, resulting in natural aspiration (breathing).

Driven by government specifications for fuel mileage and emission level control, new vehicle manufactures are forced to lighten automobiles. To reach this goal, the use of lightweight materials such as aluminum, plastic and other space are materials are utilized. One of the areas targeted for weight reduction is the engine itself. the use of plastic materials in engines includes areas such as valve covers, switches, ignition systems, fuel injector components and intake manifolds.

Dissimilar materials, in this case, plastic and aluminum, have different expansion and contraction rates. The use of plastic for intake manifolds has created problems unique to this material. Subjected to poor/improper service, deteriorating anti-freeze, inadequate ventilation and under hood temperatures that can average between 210 degrees and 247 degrees Fahrenheit, plastic intake manifolds are jailing. Original equipment manifolds have thin wall construction throughout the whole casting. deterioration anti-freeze in high mileage poorly maintained vehicles, thins the walls of the coolant passages resulting in coolant entering the combustion chamber and/or and external coolant leak. Another common failure is a result of exhaust gasses, (directed through the exhaust gas recirculation passages during normal engine operation) corroding the thin walls of the original equipment manifold resulting in loss of coolant. Engine backfires that occur can cause distortion of the intake manifold with resulting damage to the fuel rail assembly and have the potential to cause an engine compartment fire.

Results can include but not be limited to; external coolant loss, overheating, engine misfire, coolant entering the combustion chamber and out the tailpipe, wet spark plugs, warped sealing surfaces, damaged fuel rails and/or severe engine damage.

Symptoms will vary with each vehicle. Use the suggestions below to aid in diagnosing the vehicle.
*The beginning of any quality repair is always a visual inspection. Pay special attention to the area beneath the throttle body. Look for obvious coolant leaks.
*Perform a coolant pressure test. CAUTION: Not all coolant leaks are external. If coolant is entering the cylinders via the intake, the engine may be subjected to hydrostatic lock (Coolant cannot be compressed) Severe engine damage could result.
*Heavy steam vapors escaping from the exhaust system indicate coolant loss via the cylinders. The cause can be either intake manifold or head gaskets. HINT; after removal of the intake manifold, thoroughly inspect the area around the EGR passage for damaged coolant passage ways (3.8L)
*Blown head gaskets typically will affect only two adjacent cylinders. Two wet spark plugs in adjacent cylinders usually indicates a defective head gasket or possible warped cylinder heads.
*Defective intake manifolds would produce wet spark in all the cylinders. Pull 2 or more spark plugs at random cylinder locations and check for fluid (Anti-freeze) present in the plug.
*If repairs to the head gaskets are deemed necessary, replace the intake manifold as a preventative measure to avoid a potential and costly comeback (the manifold may fail shortly after the repairs).
*Misfiring engines will set the MIL (Malfunction Indicator Light) on and misfire trouble codes will be present. A scan tool will be needed to erase the codes and turn out the MIL light after repairs are completed.
*If no coolant loss is present, suspect vacuum leaks at the mating surface areas (Manifold warping is common here).

Shop for your new replacement Intake Manifold at Monster Auto Parts
Monster Auto Parts intake manifolds have been redesigned and improved. The wall material has been reinforced in the failure prone areas commonly found on original design intake manifolds. All coolant passages are reinforced to prevent leaks from reoccurring. Thicker intake walls over all and a better fillet design help to prevent warping of the manifold at the gasket mounting surfaces.

Information provided is designed and intended for professional installers. If you are unsure about terminology, procedures or other instructional references, please consult a professional installation repair facility.


Post a Comment

<< Home