As the title asks - how long should the cooling system remain pressurized on a 617? I started my car up yesterday in approximately 25* (no block heater) and drove it enough to get fully warm. Today about 24 hours later I find that there is coolant seeping from a few different areas....so I take off the cap and POOF! A big wave of pressure, I would guess approximately 10-15 psi (I believe rad cap is rated at 14psi but still should not be pressurized after sitting alll night in the cold). I've already replaced the following:
- water pump, including housing
- WP gaskets
- Thermostat & gasket
- Expansion tank cap (equivalent to the radiator cap on the w123s)
- just about every rubber hose and clamp under the hood...all clamps are as tight as I can get them, or as tight as I feel comfortable getting them on the plastic radiator parts.
- radiator itself

I'm starting to go crazy now, I feel as though my engine is constantly overpressurizing...I've replaced all the above parts due to blowouts (due to excessive pressure). I figured it was just the rad cap not releasing when it should, but I've replaced that. I'm tired of losing coolant, and I can't just throw water in there because now its below freezing almost every night. Now I'm running with the cap loose to alleviate any pressure, not really a problem since its cool enough not to deal with overheating engines, but I would much rather get it under control. Any thoughts?

__________________
TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth