Coolant Leak Mystery

[Twitchie9]

20141013_165339-picsay.jpg

20141013_165330-picsay.jpg My 1999 Venture has developed a coolant leak. I have to add fluid daily. The funny thing is that sometimes the reservoir is full, but I overheat like the coolant isn't getting to the engine. When I pop the hood, I hear pressure escaping from the approximate rear of the right side of the engine. I've attached 2 pictures of the engine and location from which I hear the leak and see steam escaping when it's hot. TIA!

[aleekat]

Most auto parts stores have loan a tool. Coolant pressure tester, deposit and get that back after you return it. You need to find the leak before you over heat and looking for a new engine or heat gasket repair.

[merc81]

I can't seem to click your one image for a better view, but I have had a couple leaks like yours in the past. Two locations to check on, both very hard to see from in front.
The hot water that feeds the heater core exits the manifold just under and behind the intake throat (throttle assembly). This is a steel tube that uses a simple O ring to seal to the exit hole of the manifold assembly. The O ring ages, gets hard and leaks. Very hard to get to without taking off most of the intake tubes/hoses/cables/etc. Pretty common leak and very cheap (new O ring) to fix.
The other is equally tough to reach, but maybe easier to see. On the firewall just behind the right side of the engine are a handful of coolant hoses and adapters that connect the engine to the vehicle front & rear heater cores. Those hoses will age, and small pin hole size leaks develop. Check in the back between engine and firewall for signs of coolant leaks.
If your coolant isn't getting sucked out of the overflow bottle when the engine cools, you surly have a leak, no need to test for it. Remember that a hot engine will push excess coolant out into the reservoir bottle, and a cold engine will suck excess back in. When that isn't happening, your coolant system is leaking.