Pontiac 3400 Engine Problems

by Edmund Gary

General Motors deployed the 3.4 liter engine in many of its U.S. built cars. Cars in the Pontiac line that used the 3.4L engine included the Pontiac Montana, Aztec, and Grand Am. Owners of Pontiacs with these engines reported on websites such as Car Complaints.com that they experienced coolant leaks and overheating problems with these engines.

Intake Manifold Gasket

The intake manifold gasket failed on many 3.4 L engines and caused either an internal or external leak. An internal leak will allow the oil and the coolant to mix together. An external leak allows the coolant to leak outside of the engine. The leaks occur around the intake manifold gasket.


The failures are linked to DexCool, GM's long-life coolant. DexCool corrodes the intake manifold gasket from inside and the plastic casing around the intake ports breaks down. The coolant seeps past the silicone tracing and gathers around the intake ports.

Check for Leaks

Checking the condition of the engine can lead a person to discovering the early signs of gasket failing. If the coolant level is constantly low in the coolant reservoir, it is a sign of an internal leak. Looking at the area between the cylinder banks may reveal whether or not the intake gasket is still sound. Puddles between the banks or under the car are signals of an external leak of the intake manifold gasket.

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