How do I replace the intake manifold gasket on a 2005 chevy Colorado 3.5l 5cyl?

SOURCE: intake manifold cover

remove oil cap steam an it should just lift off

SOURCE: Torque Spec for '99 Chevy C1500 5.7L engine lower intake manifold

On 5.7L engines, install the bolts and torque in sequence as follows:

1. Step 1: 71 inch lbs. (8 Nm).
2. Step 2: 106 inch lbs. (12 Nm).
3. Step 3: 11 ft. lbs. (15 Nm).

SOURCE: lower intake manifold gasket leaking 02 Olds Silhouette

This is basicly a very time consuming job rather than a physically hard one to complete. In order to replace the gasket you must remove the intake plenum,throttle body, and misc. vacuum hoses. The wiring harness connections must also be disconnected. Finally the intake manifold is exposed. The bolts holding the manifold to the block are removed exposing the leaking gasket. After removing the push rods and placing them in the correct order to be replaced the gasket and sealants can be removed. Finally replace everything in reverse order. Be sure to consult a GM manual for correct bolt torch specs. The correct specs for the manifold bolts usually come with the gasket. Make sure to change your oil a few times after this job in case any coolant entered the block. Also,change the thermostat and the oil seal on the distributor half shaft cap while you have everything off. Good Luck

SOURCE: vacuum leak

mine is doing the same, it's your pcv receptor on the manifold. that hard plastic cover is actually part of the intake itself, if it "came off" it would cut your intake in half. that seem seals the two halfs together. you gotta pull the whole intake off and replace it... or jimmy rig it.

SOURCE: intake manifold gasket / replace

3.8L Engine

NOTE The 3.8L (VIN K) non-supercharged engine uses a two-piece intake manifold consisting of an upper air plenum which mounts the throttle body and a lower intake manifold assembly which houses the fuel injectors. The 3.8L (VIN 1) supercharged engine uses a similar lower intake manifold. The supercharger serves as the upper manifold.
Lower Manifold

NOTE Two bolts which fasten the lower intake manifold to the cylinder head are accessible only after the upper intake manifold is removed. These bolts are located in the right front and left rear corners of the lower intake manifold. Remove the upper intake manifold to service the lower intake.
The 3.8L (VIN 1) supercharged engine uses a manifold similar to the 3.8L (VIN K), but the supercharger serves as the upper manifold.

1. Disconnect the negative battery cable.
2. On 3.8L (VIN 1) engines, remove the supercharger assembly. Please see the procedure in this section.
3. Remove the upper intake manifold using the procedure above.
4. Remove the EGR outlet pipe from the intake manifold.
5. Detach the engine coolant temperature sensor wiring harness from the sensor.
6. Remove the lower intake manifold bolts and carefully lift off the manifold.

1. Clean all parts well with degreaser, especially the gasket seal surfaces on the upper and lower manifold pieces and between the lower manifold and the cylinder heads..
2. Install new gaskets to the cylinder heads and new seals to the engine block. Carefully lower the manifold into place. Apply thread-locking compound to the bolt threads. Make sure to install the two hidden bolts in the lower intake manifold. Hand start all bolts, then torque evenly to 11 ft. lbs. (15 Nm). Follow the toque sequence, starting in the center, then working outwards in a circle.
3. Install the remaining components in the reverse order of the removal process.

1. Disconnect the negative battery cable.
2. On 3.8L (VIN 1) engines, remove the supercharger assembly. Please see the procedure in this section.
3. Tag for identification, then remove the right side spark plug wires.
4. Disconnect the ignition wires from the fuel rail.
5. Remove the fuel rail. Please see Section 5.
6. Remove the cable bracket from the intake manifold.
7. Remove the throttle body.

1. Remove the upper intake manifold bolts and carefully lift the upper intake manifold from the engine.

1. Clean all parts well with degreaser, especially the gasket seal surfaces on the upper and lower manifold pieces.
2. Install new gaskets to the cylinder heads and new seals to the engine block. Carefully lower the manifold into place. Make sure to install the two hidden bolts in the lower intake manifold. Hand start all bolts, then torque evenly to 89 inch lbs. (10 Nm). Follow the torque sequence, starting in the center, then working outwards in a circle.
3. Install the remaining components in the reverse order of the removal process.