Thread: LIM Gasket Causing Coolant in Cylinder?

It could be the lower intake manifold (LIM) gaskets. As has been said, factory LIM gaskets were a nylon material. That nylon will fail in 100% of cases, it's just a matter of time. Replace those with the newer aluminum type, which can be gotten at a dealer or through online sources like ZZPerformance.com or intense-racing.com.

(Don't get FELPRO "updated" style LIM gaskets; they're still nylon)

It could also be the plastic upper intake manifold (UIM) itself (or the UIM gasket) . Over by the throttle body (TB) end, coolant flows up from the LIM, through the UIM gasket, into the UIM, through the TB, back through the UIM and UIM gasket, back into the LIM. All the while it flows around the EGR stovepipe coming into the UIM from the LIM. The UIM plastic in that area (and sometimes the UIM gasket also) melts/warps/cracks, allowing coolant ingestion. The plastic face where the TB attaches also can warp from heat, allowing coolant ingestion at the TB gasket.

Best easy/cheap fix for that is the Auto Parts Now (APN) replacement UIM kit, which comes with new UIM gasket, TB gasket, and a steel-sleeved EGR passage in the UIM and a special reduced-diameter EGR stovepipe for the LIM (these last items reduce the long-term tendency toward plastic meltage in that area).