Originally Posted by sam_sso
The truck in last 15 000 miles has new ford heads with stock gaskets and arps egr bypass and oil new cooler. Its getting cold here so I was installing new oe ford injectors and noticed some white residue near rhe degas cap so I replaced the cap last weekend. 300 miles later i have a touch more degas white residue.
I just hooked up a pressure gauage and between full throttle and a degas psi increase only happened once out of ten full trottle runs. That time though it did get up around 17 psi. The rest of the time it seams to set itself at about 7.5 psi not caring on how its driven.
Were the new heads checked for flatness? Ford heads are notoriously not flat.
I had a similar issue before I studded. Under a load I could see 22 psi in the cooling system, and the cap would vent as it's supposed to. Now I see 7 - 8 psi coolant pressure, which is just the temperature fluid expansion pressure.