My 455 is leaking coolant. I only find it the next morning after I run it. It does not leak after sitting for an hour or so. I only find coolant on the front of the oil pan and of course the floor. It seems to lose less than a shot glass at a time. I initially tried to slightly snug the water pump bolts (large and small) and the lower hose. It still leaked. I then checked the bypass, thermostat housing, upper hose and the weep hole on the pump (all dry). All seems fine. I removed the pump yesterday as I noticed the gasket was split on one spot. I thought I had it licked! I put sealant on the timing cover bolts through the water pump and very, very thin skim of RTV on the water pump gasket. This morning I checked, the same thing! I see no trail anywhere! This engine is pretty fresh (Oct16). I have some UV dye and I am going to borrow a pressure tester today. Has anyone had a mystery leak like this? Thanks for the help..
So I figured it out today. Put the presure tester on and the driver's side long water pump bolt was leaking (dripping), it was leaking between the timing cover and the block. The gasket, from the outside, looks fine. Even when it was leaking it took me 5 mins to see where it was coming from! I cleaned the bolt again and put the sealant higher up the bolt and just a little more. Now pressurized for 5 mins and no leaks.
John mine leaks the same. Pressure holds all night long hot or cold. Fluid gathers in the distributor top of water pump area. Frank
