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Intake / Exhaust Manifold Leaks
You'd be AMAZED at how many times an errattic idle can be tracked down to intake gasket leaks where the bolts have just loosened up over time. This happens due to vibration, heat / cool cycles & the relatively low torque that keeps the bolts snugged down.
You can easily check for this by using a simple squirt bottle filled with water and set to 'stream' (not spray). With the engine running (AND acting up....) you simply squirt water along the seam between the head and intake manifold and listen for any change in the engine's behaviour.
You may have to do this from the bottom too but make sure the vehicle is securely supported and the emergency brake is on.( Do NOT do this with the vehicle in gear!)
DO NOT OVERTIGHTEN!
The studs are ESPECIALLY prone to snapping off! If you cannot seal a leak at these torque values you need to replace the gasket or inspect the manifold/head for cracks near the port.
|Component||Engines||Torque Values in Foot / Pounds ( ' / # )|
|Exhaust Manifold Bolts / Nuts||2.5L||23 ' / #|
|Exhaust Manifild Middle Nuts||4.0L / 4.2L||30 ' / #|
|Exhaust Manifild Outside Nuts||4.0L & 4.2L||23 ' / #|
|Intake Manifold Bolts||2.5L, 4.0L & 4.2L||23 ' / #|
If you have pics of your own repairs or can suggest other methods - please contribute your ideas (and pictures) to this article!
January 29th, 2007