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Pontiac Bonneville SE 1998 - Intake Manifold Issues

I’ve currently have 114,000 miles on this Pontiac Bonneville and I replaced the intake manifold last summer. Recently, I have been having issues with the intake manifold leaking a fluid on the right side of it (facing the engine) and been having dirt or some other type of fluid mixing in my fluid tank. The leak has been causing some smoking issues. Also, when I start the car in the morning white smoke comes out of the back of it. I just need some assistance in narrowing down where I need to start so that I can get this fixed. I’m assuming something went wrong in the replacement. But if anyone can direct me where to start or how to research this issue I would appreciate it. Thank you for time!

Leaking fluid on the right side…Sounds like coolant.
Dirt or something in the fluid tank…sounds like coolant/oil mix. Pull the oil filler cap, is there any white greasy, icky stuff there?
White smoke “out the back of it”…sounds like coolant in the combustion chambers. Blown head gaskets? Coolant mixing with the fuel flow in the intake? Once the engine warms up, and everything swells and seats properly, the coolant mix might go away.

I don’t want to say there are lots of problems, but it seems like there was one problem, and it might have developed into a couple more. Could still be minor at this point.

I’m not positive, but I don’t think oil flows through the intake. Coolant, most likely (probably). Replacing the manifold might have caused a problem with the gasket leaking, but that was almost a year ago now. These other issues just showed up? Did you torque everything properly, or just slap it together, and assume tight enough was good enough (not a slam, lots do and it works fine)?

I don’t think the leak and the smoke are the same issue, although they might have the same cause. Don’t ask me to explain that rationale…lol…you’d have to be in my head to get it. Yeah, they’re related, but different. Get it?

It’s normal for some white smoke out the tailpipe on the first start of the day, especially if the temperature is cold. That’s due to the steam from the normal combustion of gasoline. Combustion byproducts are CO2 + H20, and H20 is steam. It should only last a minute or two. That’s enough time for the exhaust system to warm up and turn the steam into invisible water vapor. If white smoke goes on longer than that, the faulty intake manifold gasket may be leaking a little coolant into the intake manifold too. I think you are on the right track, the intake manifold replacement may have gone bad and needs another look.

That wouldn’t explain a contaminated fuel tank though. That must be a different problem.

The coolant tank is what is contaminated, or whatever that plastic container on the left side that I put the coolant in is called. That just has a whole bunch of dirt and grime in it now. Even after cleaning it out. I’m going to try to tighten the bolts accordingly and I think that might assist with the issue. I won’t know any more information until then. Unfortunately I won’t be able to get back out until the weather clears up. Freezing rain as of right now. Thank you for your guy’s suggestions and I will report back asap.

Sorry to say but it sounds to me you have a leaky head gasket. That will allow combustion vapors into the coolant and cause the issue you see. If you do a block check that will confirm the trouble if it is so.

Take a look at your oil. Does it look like chocolate milk shake? Did you at any time overheat your engine? Why did you replace your intake manifold? You may have a blown head gasket(s).


Could also be somebody got too aggressive cleaning the sealing surfaces

I just remembered something . . . there are MANY tsbs concerning intake leaks and the GM 3.8 V6. One of them concerns some kind of passage that degrades, and you have to actually replace upper and lower intake manifolds. Not just the gaskets, but the entire intake manifolds

Were the upper AND lower intakes both replaced?