Yes, 50/50 coolant/water.

Sorry, should have mentioned - hoses are both brand new. Replaced those with the swap.

If the system was not holding pressure/leaky cap, then why would the hose bulge? Wouldn't it be the opposite?

The cap is old, should have gotten a new one when I ordered the radiator but forgot. I know it DID vent on the old radiator because I would occasionally see drips/wetness at the end of the vent hose.

Op temp before was pretty much just above 175° most of the time (maybe 180-185). Seems slightly warmer now (was running about that until my first stop/restart when it got hotter).

Can't say much about not flushing it other than I have a dirt/weeds driveway with these prickly thorn ball things that stick into everything and pop bike tires and rolling around under the car at the moment is not the most wonderful adventure. I would like to do it some time when I have a more desirable surface to get horizontal on.

Oh, one question - under what circumstances is it safe to open the radiator cap after it has been running?

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