Q: engine coolant loss on 2005 Chevrolet Silverado 1500

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loosing coolant, clicking noise in motor for a few seconds, and now "whitish-blue" smoke coming from exhaust after truck has been sitting for a while in cold weather. Has 115,000 miles on it and noise quites down or doesn't at all in warm temps. or when its still warm. New surge tank cap and water pump installed. compression test done on surge tank and passed. Any ideas? Bad lifters or head gasket? Also, I use synthetic oil and added lucas oil stablizer on last change nothing curing the noise.
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(2) Comments
Do a chemical block test to see if there is any exhaust in the coolant, this is a Pro level way to check for a head gasket issue. Then pressure test your cooling system and find the leak. Does your truck use coolant with out it leaking on the ground? If you are not getting it on the passenger floor from the heater core, then it may be getting consumed by the engine, which is another sign of a possible head gasket problem
Is the chemical block test something I can do? cooling system pressure tested ok. No external leaks have been noticed. Is the lifter noise a problem?, its really annoying and it only does it when the motor is cold. the noise is starting to prolong till about 10-20 seconds now till it warms up.
have you had truck sence new if not some body might not have changed oil like every 5000.miles motor could be nasty gunky inside