I have a 2003 Chevy silverado with 100,000 miles. It has a slow coolant leak. I’ve had it looked at by more than one mechanic. The last one told me to take it to the dealer. They did a pressure test on it. It held the same pressure for 45 min. He said that it must be the cap since they replace the cap with another one to do the test. I replaced the cap and still it leaks. Maybe a few quarts per 200-300 miles or so. Any ideas for me to check?
Perhaps you have a headgasket leaking coolant into one or more combustion chambers. SURELY the dealer checked for that. It’s a simple test. Autozone has a tool in their rental program which draws vapor from the radiator filler through a blue liquid. If the liquid turns yellowish, then there is carbon monoxide present in the radiator, and the head gasket is blown, head cracked or block cracked. Unfortunately you have to buy the liquid.
Intake gaskets would be my #1 suspect.
~Michael
My guess is on the infamous intake manifold leak. The engine may have to be at operating temperature for it to leak.
got me by two minutes Dartman 69
Great minds think alike. Those intake leaks can be tricky until they finally let go.
~Michael