My truck has a Black Water long block with studs and about 20,000 miles on it. Last week I changed the oil cooler (Again) and refilled all the fluids and every thing seemed good. This past weekend I was on my way to tow a truck for a friend, just had a empty trailer on back ( 2,500 lbs. and using tow tune) and I noticed a small trickle of coolant coming out of my degas cap. I bought a new cap, put the truck to stock and hauled a 6,00lb truck for 400 miles and no more leaks.
Here is where I have questions, not convinced that it was just a bad cap I did a bubble test tonight. The truck was cold when I started the test, there were no bubbles at first but after about a minute I had some steady bubbles. When I put the truck in gear, held the brake and built some boost the bubbles stopped when I let off they started again.
Is it possible that the bubbles that I am seeing are from the temperature of the coolant rising?
If I do a pressure test of the cooling system what pressure should I test it to? 16 psi?