JCON

After letting the car soak, I put the spark plugs and COPs back in, connected all electronics and then drove the car hard for 20 minutes to burn off the ATF and get the car hot.

disconnect fuel injectors and COP's then remove COP's, I laid them across the plenum in the order that I took them out

From there, one cylinder at a time:
remove spark plug and insert compression tester (hand tighten only) (you will need to special order the Ford Triton engine adapter, standard kits don't have the 16mm)

I laid the gauge near the windshield so I could see it from inside the car
turn key on and hold the ignition on until you see the needle stabilize, usually 3-4 seconds (will increase pressure with each turn over of the engine)
write down result
remove compression tester
reinsert spark plug
move on to next cylinder and repeat

Once you have all your results, the variance of your highest to lowest cylinder shouldn't be more than 10% (although a lot of repair shops let 15% fly as good)

Any cylinder(s) that is more than 10% needs to be wet tested to pin point the leak. to do this, you get a funnel and motor oil (although ATF fluid works also) and pour one cap full in to the cylinder. This forms a seal around the piston rings when compressed. Follow the test steps above. If your pressure increases to the same or higher than the rest, it's a piston ring issue. If nothing changed, it's a valve guide or seal issue.


While this test returns high numbers for healthy cylinders, this test should really only be used for checking variance among cylinders and to determine if it is a top or lower problem. For actually pressure, a leak down test should be performed.

BlindGUYnAR

It will be interesting to see if your results are long lasting. Like in a month or so repeat the test. I've got my fingers crossed for you.

JCON

Yeah I am hoping for the same.

Simon1

So not to make you feel bad, but check and change your oil a little more often will ya?

Best of luck with the compression issue. Very interesting and informative write up.

JCON

I plan on it now. I haven't had the issue prior to last November so I never thought about it (been running oil changes to 10-15k at a time or one year which always comes sooner). Now, I'll be looking at every 6 months.

Simon1

Try 3-5k depending on how you drive and your mods.

JCON

Definitely going to do soon then start looking at 3-4k changes. I only drive it about 6-7k a year

Simon1

I drive mine less generally. This past oil change was Jan 4. I pulled the filter and I had written the date and mileage on it. It was one day longer than a year since the last change and 3000 exactly. Just a coincidence, but my son and I had a good laugh over it.

moosestang

I used to change mine every 3k, but have since moved to 5k. Reason being I changed to 10w30, which will not shear as quickly as 5w30, everything else being equal of course. I am not nice to my motor either. I regularly beat on it before it's up to operating temp. I live and work less than 1 mile from the interstate and I can't use an onramp without wide open throttle in 3rd gear.

I have never had to add oil between changes and i check it often.

JCON

I never had to add until last fall. Something happened and I am not sure what. Going to check my level in the morning and see if it's still full. Has been for a few weeks now. It's so strange. Car definitely feels solid. I absolutely love opening it and letting it roar with the top down.