Thanks for responding I did read a post from you from another forum when you checked yours (2 years old I think-- maybe more).
First would you agree with this statement. If your pressure gauge goes up very quickly during WOT and stays up (like 15-16psi) after then you have blown head gasket(s). AND most likely if your gauge goes up and then back down quickly after WOT then not a blown head gasket?
I have been taught that if the pressure rises rapidly and drops rapidly, correspondingly with the acceleration pedal, it is probably an EGR cooler. If it goes up and stays up, or is slower to dop, it is probably head gaskets.
To use the pressure as a test, you must have a good degas bottle cap.
Do you still have an EGR system?
Ok mine_ On my test second day-- I know the first day I had a bad cap.
ECT was 190-195F During WOT test.
Was able to get it to 13 psi only on one time on a long up hill. The rest of the time I could only get it up to 10psi on WOT test. It would go up as soon as the boost kicked in and come back down just as quick when boost came back down. The coolant psi responce was like it was connected to boost press. (I know it is not but just try to explain what it did).
This sounds like an EGR cooler to me, but that doesn't mean that you also could have head gasket issues.
Not sure what psi was when ECT was 165-175F. But do know it went up as temp did.
To vary with temperature is normal
Also after I did my WOT test and ECT was running 190-195F and parked and let it idle the PSI came down to 5. After shut down it would drop to 4psi and stay there. It would run a steady 7psi without getting onto the gas hard when ECT's were 190-195F.
I'll have to see if I get a drop in pressure when idling. I do not think I do. One thing to understand is that when a cap relieves, it will weaken. To me it sounds like you have a weak cap again, but I am not quite sure how many caps you tried. I really prefer the "revised" OEM cap. They hold up pretty well, but Ford still says replace them if they have relieved very many times (at the 16 psig set point). I have no experience with the aftermarket caps and their reliability.
level in your degas bottle Level is 1/2"-3/4" below new sticker line when cold. When up to operating temps it is in middle of old min and max lines.
My level varied that much when I had gas in the system (didn't purge it completely after a coolant flush. Now, I do not see quite that much of a variation in level.