I have a 2000 Silverado 5.3L that is loosing coolant

I have to fill the surge take with every tank of gas. There are no visible signs of a leak, there is no oder of coolant. I have changed all the hoses. I have
pressure checked the system, it holds 15psi over night! I have pulled the spake plugs to see if one is overly clean as a sign of coolant burning off in a cylinder, they are all the same tan color. The oil is clean no milk shake. The truck runs great. It runs right at 195 as it should.
When I was inspecting my intake manifold I discovered it has as vacuum leak at some of the cylinders. My OBD2 meeter shows the O2 sensors spike when I spray break cleaner at the base. So I will deal with that in the near future but that should not affect coolant.
Any body please this is driving me nuts!
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Rossco wrote:

Check the line and overflow tank itself. One of those could be cracked and they don't get tested as they are after the cap.
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Steve W.

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On 8/24/2015 11:10 PM, Steve W. wrote:

My 98 Blazer has a leaky over flow tank. I've been using a length of hose and a two liter soda pop bottle for overflow system. My radiator has a serious leak, and I need to fill my over flow ever morning. Some time later this year, I will put some epoxy on what I think are the leaks.
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Christopher A. Young
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replying to Rossco, Rossco wrote:

signs
spake
The
at
that
Thanks guys, found it. It would hold 15 psi cold for 24 hr but when I warmed the engine up to 195 and then pumped up the pressure to 15 psi coolant dripped out from behind the water pump. Heat was the answer. So its a simple water pump job.
Good input I was leaning toward the surg-tank and cap myself. Thanks all
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