Engine Coolant Loss

[Andy Clark]

Here's my question: is there a manual valve somewhere in the cooling system on a '95 Cummins 8.3C in a Beaver Pat with which to bleed off any entrapped air in the coolant hoses/pipes/galleries?
The reason for my question is this. Early last summer, I changed out my coolant and filter and filled the system with fresh including the overflow bottle, filling it to the "minimum cold" line. I've driven about 3000 miles since then with no overheating, and the bottle liquid level came up to the "normal" level (or a bit higher) line during/after running, so no problem, eh?
Well, maybe and maybe not. We've had some pretty cold weather recently, so yesterday I visited the coach to ensure all was well. When I looked at the overflow bottle it was empty with no signs af antifreeze on the ground or elsewhere. It was up to the "minimum cold" line when last I looked at it a couple of months ago.
I'm wondering if there's air entrapped in the sytem which contracted in the extra cold temps and pulled the bottle contents back into the engine system. Air expands and contracts a lot more than liquid and I can imagine a scenario where this air contraction could pull antifreeze back out of the bottle through the (one way) radiator cap.
There doesen't appear to be a leak within the engine system because when I undid the header tank (radiator) pressure cap, it was full, and there was slight pressure within, forcing a little coolant out. Since the ambient temp yesterday was much higher than recently, the air could have expanded and caused this pressure build-up. If the antifreeze was leaking internal to the engine, I don't think there would have been pressure in the system after not having been run for several months.
Waddya think? Am I being too "anal" (not terribly unusual for me!!).
What other problem might I have?
Thanks
Andy

[Marty and Suzie Schenck]

Andy, I can't speak for Cummins but my CAT, when refilling the cooling system the manual says to fill it slowly as not to trap air or get air pockets. I would think you could call any Cummins dealer and ask what they recommend. Marty

[Gerald Farris]

Andy,
If you have driven the coach 3,000 miles since the coolant was changed, there is no trapped air left in the system. The cooling system is designed to purge any trapped air with normal usage, especially as it goes through the hot to cold cycles. The low level in you recovery tank is just caused by the low temperatures. So remember that you will not have to worry about that problem if you stay south of Interstate 10 in the winter.

Gerald  

[Andy Clark]

Marty and Gerald, thanks for the replies. After a bit of searching, I found the bleed valve but based on Gerald's comment I have not touched it. I think that you have hit the nail on the head, so to speak, Gerald.
One thing I did note in my investigation today was that when I started the engine (with no accompanying "gronk" noise or white smoke , thank goodness), the coolant bgan to infiltrate the bottle long before the engine had ANY temperature in it. This suggests to me that I have a failed pressure cap, so I'll be ordering one of those tomorrow.
Again, thanks guys, for taking the time.
Andy