Hello. I have a slow loss of coolant. I can't find where the leak is. I rented a pressure tester and could not build pressure. I thought it was the seals from the water outlet housing, which was a cause in the past, but after replacing the seals this time, I was still unable to build pressure with the tester. I used the tester to check the cap from the reservoir /expansion tank and it properly holds pressure. The oil on the dipstick is a normal color, not milky.