LLY engine hours and air in coolant - 2 questions

[rapidoxidationman]

On engine hours: I noticed that while my truck has over 124,000 miles on it, the engine hour meter has only about 648 hours on it. Thoughts on the obvious conclusions (193mph average or a swapped out engine not too long ago)? Is resetting the hour meter something only the dealer can do? Any thoughts on ways to find out why the meter was reset (or why the engine was replaced)?

On air in coolant: squeezing the upper radiator hose makes a sloshing sound, whether hot after running or cold before starting in the AM. No signs of oil in coolant or coolant in oil, and the expansion tank fluid level doesn't seem to fluctuate. I hesitate to admit that I've gotten a slight whiff of coolant outside the truck on occasion, as has a mechanic friend, but no signs of a leak and like I said, I've not had to add any dexcool. Am I being paranoid with a new-to-me truck or am I looking at head gaskets?

[Kennedy]

My LLY has a messed up hour meter as well. Not sure on the why, but my first suspicion is the cluster itself.

The sloshing is normal and you will also hear a click from the thermostat housing as well. If the HG leaks you'll build a lot of pressure and typically will see low coolant light along with heater function coming and going.

[CoyleJR]

My LBZ hour meter reset to zero when I removed/replaced the batteries. I posted the problem on TDP and the responses I received indicated that some trucks reset to zero and some do not reset to zero when the batteries are removed. ??????

Good luck with the new truck.
John

[rapidoxidationman]

Given that they're not the original batteries in the truck I can go with the battery reset idea for the engine hour meter.

On the coolant though, everything I've read about Dexcool says it is great stuff - when it is not in contact with air, which can cause corrosion issues. Is there a way (or a reason) to bleed the air from the system? I'd've thought it would pretty will bleed itself, but maybe no?

I know there's an air bleeder plug on the thermostat housing but are there others?

I've removed the overflow tank cover when the truck is hot to relieve the pressure with the thought that as the engine cooled it would suck fluid back into the system and that repeated "depressurizing" would eventually get all the air out. Thoughts?