lower intake leaking

I have a 2000 Grand Prix GT 3.8 with 65,000 miles on the clock. My wife took the car into a dealer for an oil change. When i got home she hands me some paperwork from the dealer that says "lower intake leaking" $650.00 to fix. Now I am a backyard mechanic but not familiar with the GP engine. Give me an old 350 cid or 302 cid and no problems, but this new stuff, damn. I know what an intake manifold gasket is but a lower intake gasket and an upper intake gasket? could someone explain to me the difference between them? Also i have not noticed any lose of power or coolant lose. I do have a problem with a mushy brake pedal that i was going to change out the brake booster because it appears to be a vacuum problem. Could that be why the dealer is saying a leaky lower intake? thanks.

First off, going in for an oil change, you can't tell if the lower intake gasket is leaking.........you may see some oil seepage at the corners of the lower intake, or you may have a valve cover that is leaking, that may look like a lower intake leak....

First thing I would do, is just wash down the engine, in the four lower corner areas of the lower intake and then keep an eye on it....seepage happens, and many times it is nothing to worry about......your vehicle is 13 years old, and over time, oil seepage collects dirt and looks worse than it actually is....more often than not you may have an upper plenum gasket leak, or throttle body gasket leak.....

The upper plenum, is that big black composite plastic mound sitting on top of the engine.....Where the throttle body is attached to it, there is a gasket that can leak coolant on the bottom side of the joint....

The plenum sits on top of the lower intake...separating them is one big pastic gasket that tends to leak....when it does, you will see gunk built up around the injectors...

The lower intake is attached to the heads with plastic gaskets......at the far ends are pieces of rubber seal that prevent oil leakage on the outside edges where the bottom of the lower intake comes in contact with the block....a joint is formed there between the plastic gasket and the seal...in this joint, RTV is applied to prevent oil leaks....this is the general area where you could have oil seepage.......

I would wash the engine down first, then keep an eye on the engine for leaks.....also check your oil and coolant levels to see if they are dropping...

First off, going in for an oil change, you can't tell if the lower intake gasket is leaking.........you may see some oil seepage at the corners of the lower intake, or you may have a valve cover that is leaking, that may look like a lower intake leak....

First thing I would do, is just wash down the engine, in the four lower corner areas of the lower intake and then keep an eye on it....seepage happens, and many times it is nothing to worry about......your vehicle is 13 years old, and over time, oil seepage collects dirt and looks worse than it actually is....more often than not you may have an upper plenum gasket leak, or throttle body gasket leak.....


thank you for the reply. Not that i am a procrastinator but i never took the car in for the recall on the back valve cover gasket leak. I believe it was the valve cover gasket. I bet it is the valve cover leaking and not the lower intake. thanks again for the info. i will wash it down and keep my eye on the oil and antifreeze levels.

The upper plenum, is that big black composite plastic mound sitting on top of the engine.....Where the throttle body is attached to it, there is a gasket that can leak coolant on the bottom side of the joint....

The plenum sits on top of the lower intake...separating them is one big pastic gasket that tends to leak....when it does, you will see gunk built up around the injectors...

The lower intake is attached to the heads with plastic gaskets......at the far ends are pieces of rubber seal that prevent oil leakage on the outside edges where the bottom of the lower intake comes in contact with the block....a joint is formed there between the plastic gasket and the seal...in this joint, RTV is applied to prevent oil leaks....this is the general area where you could have oil seepage.......

I would wash the engine down first, then keep an eye on the engine for leaks.....also check your oil and coolant levels to see if they are dropping...

thank you for the reply. Not that i am a procrastinator but i never took the car in for the recall on the back valve cover gasket leak. I believe it was the valve cover gasket. I bet it is the valve cover leaking and not the lower intake. thanks again for the info. i will wash it down and keep my eye on the oil and antifreeze levels.

The 3.8 is known for LIM gasket failures. They are not hard to change if yours is leaking. When you replace them go to Rockauto and buy the metal gaskets and you will never have to worry about the LIM gasket again. Also check your collant elbows for leakage. These also tend to be a failure point. Rockauto also carries aluminum elbows so you won't have to worry about them going bad. I would also check and replace the upper intake gasket, vavle cover gaskets and the TB gasket for safe measure while you are in the engine. These parts are not too expsensive and pretty easy to install.

I have a 2000 Grand Prix GT 3.8 with 65,000 miles on the clock. My wife took the car into a dealer for an oil change. When i got home she hands me some paperwork from the dealer that says "lower intake leaking" $650.00 to fix. Now I am a backyard mechanic but not familiar with the GP engine. Give me an old 350 cid or 302 cid and no problems, but this new stuff, damn. I know what an intake manifold gasket is but a lower intake gasket and an upper intake gasket? could someone explain to me the difference between them? Also i have not noticed any lose of power or coolant lose. I do have a problem with a mushy brake pedal that i was going to change out the brake booster because it appears to be a vacuum problem. Could that be why the dealer is saying a leaky lower intake? thanks.

Fixing the lower intake leak is a huge revenue source for repair shops. I would imagine that every time they get one of these engines in they hand out that paperwork. I've had the same thing done to me with a '98 Malibu and I said "Thanks for pointing that out, but no thanks." Usually, it is the coolant that leaks that soon needs to be repaired. Just keep a close eye in the coolant usage. Also, check your oil filler cap for milky sludge. And finally, I thought the recall on the valve covers only addressed the front one, not the back one. The front one is the one that will get flooded when you stomp on the brake.

Fixing the lower intake leak is a huge revenue source for repair shops. I would imagine that every time they get one of these engines in they hand out that paperwork. I've had the same thing done to me with a '98 Malibu and I said "Thanks for pointing that out, but no thanks." Usually, it is the coolant that leaks that soon needs to be repaired. Just keep a close eye in the coolant usage. Also, check your oil filler cap for milky sludge. And finally, I thought the recall on the valve covers only addressed the front one, not the back one. The front one is the one that will get flooded when you stomp on the brake.

I was told it was the back one, I could be wrong. They said it was a fire hazard

The recall is for the front one.....

Next oil change I'd send a sample off to Blackstone Labs for analysis. If it is the lower intake gaskets, they aren't that hard to do. When I did mine I took pics and used a silver sharpie to label all the hoses and connectors. I didn't have any problem putting it back together.