does the WP always....

weep from the weep hole when they go? Could it somehow fail without weeping?

88 4.0 aw4 - took betsy (baatsaeh) out after sitting months, and overheated. I have serviced all but a few stock lines, and heater core, and the bottle almost blew up, but shows full.
maybe the tranny is overheating the water in radiator? is that possible?

Thanks

Ok. Renix. Pressure bottle should be no more than 1/3 full, otherwise the expanded coolant has no place to go. Has your pressure bottle cap failed? When they fail and you lose pressure your boiling point drops and coolant will come out without overheating. Try tightening down the cap--does it seem to "pop" like its stripped? Common problem. You can put a worm clamp around the cap, tighten the cap down just short of popping, then tighten down the hose clam--pretty Ghetto. I recommend you replace the cap with a Stant 10244 cap--it won't "pop" loose, lower profile so it doesn't impact the hood when the bottle expands and promote cracking of the bottle, and the pressure is a little higher and that raises the boiling point of the coolant.

Also, 50/50 mix of ethylene glycol and distilled water is just an industry winter/summer compromise. You should run 30/70 from late spring through early fall--30 ethylene glycol and 70 distilled water.

Can a water pump fail without leaking--yes, the impeller could have eroded or broken--not unheard of.

How about you describe the overheat--at highway speeds? At idle/in town driving?