02 impala 3.8 intake plenum


Old 07-27-05, 11:08 AM
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Question replacing 02 impala Ls intake

my 02 impala LS has the 3.8 and from what I've read the intake plenum is plastic and will crack eventually. If this goes undetected it can be catastrophic and cause coolant to get into the oil and eventually cause the motor to lock up. For those that read this all series 2 3.8's have this problem. My question is, how involved is this repair? There are replacement plenums that have been reinforced and do not have this problem so I'm thinking about doing it myself when failure occurs. The car has 65000 miles on it so it won't be long.

Last edited by repbuddy; 08-05-05 at 10:52 AM. Reason: to change title
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Old 08-05-05, 10:50 AM
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Has anyone out there ever had to do this repair?
Old 08-05-05, 03:54 PM
Join Date: Aug 2005
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No you are mixed up. The plenum melts by the throttle body. There is a revised one out that has bigger passages. I know i have seen them in pepboys catalogs. usually they are around $280. Thats why most people wait till it happens to them. Some just don't melt and leak the coolant in and some do.

Yes i have done my fair share of them. Its pretty straight forward and easy to do. Just make sure you get the gaskets. If you need to know how chilton's makes great automotoive books.
Old 08-05-05, 07:18 PM
Join Date: Feb 2005
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I have done probably 100 or so. We used to replace the plenumn, but GM came out with a TSB instructing that only the plenumn gasket is to be replaced, unless, as shottys stated, the one port gets burnt and distorted. When these gaskets fail, this allows coolant into the cylinders, between the pistons and heads causing it to hydrolock. We simply pull the plugs and roll the engine over to drain the cylinders. After that, we clean the cylinders out, and blow them out with compressed air. We usually replace the spark plugs. After the repairs, we do an oil change and we're done. The new 3.8L has an aluminum plenumn which, in my opinion, and alot of others, should have been used from day one.
Old 08-05-05, 08:07 PM
Join Date: Aug 2005
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Thats right every mechanic has done atleast 1 if not a few hundred literally
Old 08-08-05, 06:40 AM
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Such a simple fix but I guess GM has a binding contract with the supplier or maybe they're making money off the repair. I'm gonna keep a close I on it until it fails and then do the repair. It seems to happen to most people before 100,000 miles so it won't be long. Thanks for your help guys!

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