Engine Overheat - keywords lower manifold PIP3909

This PI was updated to include the L26 engine. Please discard PIP3909.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some customers may comment about a possible overheating condition. Upon inspection you may find that while the coolant temperatures on the I/P cluster and Tech 2 appear normal, the engine appears to be running hotter on the front bank and in severe cases, sounds similar to an incomplete combustion event may be heard.

On the L32 Supercharged Engine: After the engine has been allowed to cool, remove the thermostat housing and thermostat. See SI for information on thermostat removal. Once the thermostat has been removed inspect the inside of the lower intake manifold for a casting flash in the coolant passageway. If present the casting flash will appear in the area shown (1) in the picture provided. If the casting flash is present you must replace the lower intake manifold. Do NOT attempt to remove the flashing. If the casting flash is NOT present, then something else is causing the overheat condition. See SI for additional diagnostic information.

On the L26 (non supercharged) 3800 Engine: After the engine has been allowed to cool, remove the lower intake manifold. See SI for information on lower intake manifold removal. Once the lower intake manifold has been removed, using a flashlight, look for the presence of a casting flash or partial casting flash inside the coolant passageway in the manifold. There is one passageway on each side of the manifold where the manifold attaches to the cylinder head. Each passageway connects to a main passageway that runs parallel along the center underside of the manifold. If the casting flash is present it will appear where either side passageway connects to the main passageway. If there is a casting flash or partial casting flash present, the lower intake manifold must be replaced. Do NOT attempt to remove the casting flash. If the casting flash is NOT present, then something else is causing the overheat condition. See SI for additional diagnostic information.

All 3800 Engines:

If a lower intake manifold is replaced because of a casting flash, contact Jim Kelly on (586) 492-5612 and he will supply you with a parts waiver and shipping information on where to send the old manifold.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.