How to replace intake gasket on 99 Pontiac Grand Am

you have a GM common problem and that is a bad intake manifold gasket. GM change the gaskets to plastic and they crank and leak causing over heating. here is a picture of one i took from a 2005 pon. bonneville with 74,000 miles on it

Did you try Head gasket fix I had 99 3.4 works well?

If you haven't replaced the thermostat yet, try that next.

Please see my tip at http://www.fixya.com/cars/r5929960-s_thermostat . These are generic instructions. If you get stuck or need specific instructions for your car, please get back to me with model, year and engine info.

there ia a procedure for this in a repair manual at your local auto parts store

upper or lower e-mail me at bigwheels4now@yahoo .com

i think you have an air leak with this new gasket you fitted that would make the engine run faster as its running very week and drwing secondery air , witch is why you have low presher,, the thumping you get when you put the car in gear is becouse its ticking over too fast it could brake a drive shaft if you dont sort the manyfold gasket out soon, check all the bolts around the intake are tight first, but my gess is its leaking badly

Are you really wanting "FREE" information? or are you wanting "GOOD" information?
Replacing intake manifold gaskets on a 3.1L or 3.8L Pontiac Grand Prix is no walk in the park for someone with little or no experience. There are a lot of problems with these engines that only experience can teach. I recommend having it done professionally.

However, if you really want to try to do it yourself, you are going to need the best information available and you will probably have to pay for it.
An excellent option is to go to http://www.alldatadiy.com/
There, you can subscribe to a single vehicle for $26.95
This will get you all of the repair information for your car that is available to professional shops including component repair instructions, wiring diagrams, vacuum diagrams, Technical Service Bulletins, etc.

did you bleed the air from the system? how do u know u don't have a leaking head gasket, have u had it checked with a gas analyzer?

Are you sure it needs a head gasket? These are common for just having leaking intake gaskets and that is alot easier and cheaper to fix.

That is an intake backfire, meaning you have the valve timing wrong. Not quite sure right now on what it should be but check timing belt position and valve timing gear positions.