3.8L replacing upper intake manifold & gaskets

I have a 99 3.8L grand prix. It may be getting oil in the coolant, it looks muddy and started running sluggish. The low coolant light came on briefly and went off. The oil seems to be over-filled. Mechanic has said this is a common problem with a lot of GM vehicles. My husband and son are going to attempt to replace the upper intake manifold and upper and lower gaskets. They will be needing instructions and diagrams to do this. I was hoping someone can help or point me in the right direction. AND, how difficult of a task will this be? My son has rebuilt quiet a few 4-wheeler, dirt bike and lawn mower engines, but is not very organized. My husband is also mechanically inclined, but not very patient. What they lack together is compatibility under pressure!!!! And this is MY CAR they will be working on!!

Any help or guidance will be greatly appreciated.

Thank you,
Peggy

try autozone's website, they have some repair proceedures posted there. If not, buy a repair manual (under $20) and follow the instructions. You will need a torque wrench capable of going down to 89 in/lbs. I just recently did one of these jobs and was done in less than 2 hours. It is not a difficult job, but it does require the fuel rail to be removed, so make sure you replace the fule injector o-rings to avoid a possible fuel leak.

Welcome to AF.

Doesn't sound good. After the repair work before sure to drain/change out the engine oil and replace the oil filter. Also, just to be safe you may need to do a cooling system flush.

As Rich mentioned a UIM plenum and gasket/throttle body job may take roughly two hours. However, if you plan on doing the lower intake manifold gasket it will take longer.

Send me a PM email. I have the UIM/LIM R&R procedure in a PDF file format to include all applicable GM TSBs, parts listing and torque specifications.