Need help with coolant leak
So long story short, got a 96 eddie baurer 4.0l. Started leaking coolant. I noticed a leak and by dumb luck i found its coming from under the thermostat housing. not where the hose clamps onto the housing, from undernearth and behind the housing. It trickles when the trucks idle, when you rev the engine its a stead solid stream. Any ideas where or what is causing this?