This is a common problem when you have an intake gasket leak. The intake manifold can leak coolant into one of the oil passages or externally. You are correct that the vehicle will pass a compression test if the intake manifold gasket is leaking.
Your first step should be to confirm the intake leak by pressure testing the coolant system to verify the leak. If no external leak is found then you should pull the oil dipstick and verify that there is no coolant mixed with the oil.
There is a Technical Service Bulletin to replace the lower intake manifold gasket with an updated gasket.
Here are the updated parts required for the repair:
Here is a diagram of the lower intake manifold
Here is the procedure to replace the intake manifold gasket:
Remove the upper intake manifold. - Upper.
Remove the valve rocker covers.
Remove the fuel rail with injectors and position aside.
Remove the power steering mounting bolts. Position the pump aside.
Remove the inlet cooling pipe from the coolant outlet housing.
Remove the heater by-pass at the coolant pump and the cylinder head.
Remove the radiator hose from thermostat housing.
Remove the water outlet housing. Important: Retain the washers in the same orientation on the center bolts.
Remove the lower intake manifold bolts.
Remove the lower intake manifold.
Loosen the rocker arms. Important: Keep the pushrods in order. The pushrods must be installed in the original position.
Remove the pushrods.
Remove the intake gasket.
Inspect the flatness of the inlet flanges.
Clean the following items:
- Gasket material from the mating surfaces
- Excess RTV sealant from the front and the rear ridges of the cylinder
- The block
- Sealing surfaces Use degreaser in order to clean the sealing surfaces.
Please let me know if there is anything else that I can do to assist you.