Thread: LIM Gasket, Head Gasket, or bad sensor?

Originally Posted by GTFiske

For those who read this in the future with any of the above symptoms.. the problem turned out to be the Upper Intake Manifold (Plenum). When the old one was taken off, the LIM was FILLED with coolant. Scary stuff.. it could've ruined the motor. Luckily it wasnt running when it hyrdolocked.

An easy way to test is to take off the the intake... open up the throttle body to see any signs of coolant (fresh or residue). But that isn't always the case.. just mine.

For those who don't know (which I didn't prior to this) the plenums are defective and melt/corrode fast around the EGR valve. The new valve is much narrower so the heat of the aluminum won't melt the crappy plastic intakes.

New LIM gaskets, UIM/plenum with new gaskets, thermostat, plugs, and 3 oil changes... the system is running great. SES light went off on its own and now getting 25+ mpg.

dang.... learn something new everyday.... was it sorta like a black sludge looking stuff? because ive had that coming out of my throttle body before. i just cleaned it out and didnt really think much of it.... ill have to check my egr if thats the case you think just changing the egr will prevent it from failing totally?

Originally Posted by GTFiske

It was weird.. it was literally straight dexcool coolant ON TOP of the lower intake manifold. Oil I believe is a sign of the head gasket beginning to deteriorate.

The throttle body had crusted orange/pink residue in the grooves and around the sensor. But there was a black build up on inner side of the throttle body.

For the EGR valve.. you could replace it to prevent any further damage. But you should check the plenum when you have it off anyway to see any signs of corrosion around the valve. The two holes opposite each side of the actual valve was where the problem truly was. The coolant was boiling around the valve to the point that it would splash up and corrode it. Over time.. it just completely wore through the gasket and plastic.

i just replaced my headgasket not too long ago it blew... so it explains the black sludge. that was there before it blew though.... i replaced my egr there wasnt corrosion on the manifold but there was on the egr im getting better gas milage and its running smoother too. this a problem with any 3x00 motor? btw the whole corrosion issue is new to me never heard of it happening before.