The over flow cap itself is leaking a little as it comes up to.pressure. the leak is running down the line that goes towards the firewall and dripping on the exhaust manifold. This could honestly be as simple as a Failing Cap. I am running to get a brand new one. I have not pressure tested yet only because my gut believes l have full compression and am chading a simple leak in the system. Process of illumination however if this doesn't cure my ills l will have to go get the test kit next. No options left after this.