Cracked Head

I have an 1984 gmc sierra 3500 pickup/350 propane. The water in the overflow is full and my radiator doesn't seem to want to take the fluid back from the reservoir "even though the fluid is very low in my rad. I
think it might be a cracked cylinder head "propane has cracked the heads in the past". I took it to a radiator shop and he tested my coolant for hydro carbons, and found none. How accurate are those testers, and does this mean I probably don't have a crack? I'm going to change my radiator cap, see if that helps. Any help would be appreciated. It passed the emmisions test last week. Can it pass with a cracked head. Don't know if I'm losing fluid in to the cylinder or just in to the overflow.
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Have you checked the overflow hose for cracks? If cracked, it will suck air instead of coolant. Dave
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coolant to be blown out there will be a noticeable coolant loss from over flow tank. I've used leak detection systems to check for gases in the coolant the good ones are accurate.
Jim .J
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Replaced the radiator cap yet? how about checking the hose for blockage or cracks?
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Steve W.
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now transferring back and forth like it should. Thanks for your help...
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