So I decided to do a compression test on my 1990 F150 XLT 302 today, and I had the engine fairly warm(not cold, not hot). Tightened the tester by hand and tried to make sure I tested each cylinder exactly the same. Here are my readings:
4-159 8-155
3-178 7-168
2-181 6-175
1-179 5-184
Is this pretty bad off? Thanks guys.

 

Looks pretty good to me for a 27 year old engine. Did you hold the throttle open during testing?

 

No I didn't realize I had to do that until I was almost done and it was getting late so I just finished. Either way, why would # 4 and #8 be so much lower? I am leaking coolant behind #8 and it's running down bellhousing. Also I'm shooting water out my tailpipes, it misses some not too bad, and inside my oil cap is a yellow greenish color. There is no oil in my coolant and no coolant in my oil. Is that just condensation? The drops that come off bellhousing have oil but im assuming its collecting oil on the way down to the ground bc my motor has alot of old oil on it. By the way, it only has 90,000 miles on it.

 

I would say you have a leaking head gasket, and would replace both while you have it torn down. I wouldn't be concerned with the variation between cylinders at this point. I think you will be back within 10% of each other after you replace the head gaskets.

 

Ok I'll do that. Thanks man.

 

I agree you need to get another test done with the throttle blades open.

And #8 cylinder is showing low due to the #8 runner from the plenum that has the PCV valve line attached to it. There were reported cases where the #8 piston grenaded due to the sludge and contamination. I have a '92 302, that has a replacement piston in #8. It was done sometime in '98-99 according to the rod bearing. There is a TSB about moving that line to the center of the plenum and moving the brake booster line to the back of the plenum where the original PCV emission line was.

And as far as water out of the tailpipe, I'm leaning towards condensation. That also could be what your seeing on the oil fill cap. Both the water and the condensation are common and typical of an engine that doesn't get up to operating temperature.

That milky froth on the oil fill cap always seems to have people panic but most of them don't run the engine long enough to burn the condensation off inside the engine. It's always typically worst in the cold of winter and it's not a sign of head gasket leak.

Let us know what the weather has been like, how long you run the engine, and that can help us further.

 

My pcv valve is on the #4 side and on the driver side I have a hose from my oil fill to airbox. I don't know lol all I know is I leak coolant near the back of #8 head. Not a lot unless temps drop below freezing. Weather here is around 28-40 degrees right now. I don't drive far at all. A mile a day. I had heard that the engine wasn't getting heated up enough to burn it off so I have been letting it idle longer before I leave and when I get home. My temperature doesn't even go to normal. Stays between cold and normal but engine gets warm and heat works pretty good.