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Q: Roland, does the 2007 4.7 liter with the plastic intake manifold have coolant passing through to cool the manifold?

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The teenage daughter ran my 2007 Jeep Commander hot. After inspection, I discovered coolant in almost every cylinder. After vacuuming all the coolant from the cylinders (approx. 1/2 cup of fluid total) A compression check on all cylinders shows no compression loss. this has me scratching my head as I was expecting blown head gaskets. A local mechanic suggested that the plastic intake manifold may have gotten warm enough to melt or warp allowing coolant to travel to all the cylinders and suggested replacing the intake manifold. I don't believe this plastic intake manifold even has coolant passing through it. Am I wrong and what do you suggest my next move should be? Thanks in advance for any help you may have to offer.

A: Hello. It does not appear that the intake m...

Hello. It does not appear that the intake manifold on that model has coolant passages, so it is unlikely that that is the cause of the issue.

I would still carefully examine the intake manifold for any signs of warping, however, as plastic manifolds are more susceptible to warping than aluminum ones.

If the compression test was performed on a cold engine, it may be possible that a cold engine helped seal the pressure. If it feels safe to do so, I would start the engine, warm it up to operating temperature, and then retest the cylinder compression. There are certain cases where the head gasket is blown or the cylinder heads are warped, however, only once the engine is warmed up and the metal expands. If you’d like a second opinion on the car, a certified expert from YourMechanic can come to your car’s location to inspect the overheating problem and diagnose the issue properly.

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