Re: Leeaking on hill only!!!
If the bollte is too full, for sure it can leak out when up hill. There is an overflow line at the aft side of the bollte which for some strange reason ends on top of the PCM connectors. If the level is ok, there can be a crack or other damage to the overflow bottle. Thermostat or radiator cap should not cause a high level in the overflow reservoir, as far as i know. A stuck thermostat causes a too high or too low engine temperature and when the radiator cap doesn´t work well, there will be no pressure buildup in the engine cooling system, which could cause a little higher level, but not that much that it will flow out of the reservoir.
JEEP Grand Cherokee 4.7 Lmtd 2004
HID 8000K in low and fog / Quad Squad member
Monroe Reflex shocks /
Pirelli Scorpion ATR 245/65/17/
Transgo reprogramming shiftkit.