Ford Enthusiast

[ABE]

You need a compression test on all 8 cylinders. The gauge is relatively cheap and should have a hose with the correct threaded fitting for your plug thread and a valve to release the pressure (cheaper ones press into the plug hole and give a momentary reading). The gauge screws into the plug hole (after removing the plug) and you have someone else turn the engine over for about 5 or 6 turns. You should remove all the plugs so that the engine turns quickly and easily and test all cylinders in one session. You are looking for 3 things in particular:
1. How fast the compression rises to max level, 3 turns should max out a good cylinder;
2. How high the reading;
3. How consistent the readings among all 8 cylinders.

A cylinder with about 150 psi is usually good, 80 psi is too low to fire the cylinder properly, 50 psi is basically no compression. All cylinders need to be close in reading or you have a wear problem or something is broken. Adjacent cylinders with low and identical readings usually indicates a head or gasket failure between those cylinders.

Since you have trace amounts of coolant then you need to drain the coolant to avoid coolant getting into the oil and taking out your crank and every other engine bearing. Also, drain a little oil from the pan looking for coolant which will settle in the bottom of the pan. Check the oil for a milky look, and drain it all if suspicious, and change your filter.

The coolant can enter from head being warped, failed head gasket(s), intake manifold/gasket failure. The engine compression test will allow some diagnosis. If all cylinders have good compression (150 or thereabouts) the heads and head gaskets are likely good. Coolant in the cylinders is likely then from the intake manifold or its gasket.

Hope this helps.