AScarlett08

I have a 1999 F150 4.2L V6 that I just replaced the Water Pump and Thermostat and their respective Gaskets. I used Ultra Black RTV with the gasket on the W/P but just the gasket on the thermostat. We got everything back in and torque to specs. Let it sit for 24 hours. I then poured 1 jug of coolant in and everything was fine. I thought I had a second jug and I didn't so I drove to the local oreilys and grabbed one and came back. Still no leaks. Awesome! Right? Well I then start to pour the second jug in and about half way through that jug its like someone opened a faucet and coolant was just pouring out onto the ground. Sweet!
I looked everywhere to see it and the leak is hidden just out of site. However, I do see it pooling below the thermostat just above the w/p behind slightly farther back towards the engine itself.
Because of the amount of flow I had with no "seeping" Im guessing there might be a tare in a hose or I just barely missed fitting a hose just right? The fact that is was fine until I put about 1.5 gallons of coolant in but it was ok with 1 gallon mean I have something not fit on there correctly at the upper end of the coolant system. Right? Or am I crazy? I will be double checking my hoses this afternoon but I thought I would reach out here and see if anyone else might have seen a similar issue.

white89gt

I suspect you may be leaking on your crossover piece. There are gaskets on them that can go bad on you. Sniff around in that area and see if you can see anything.

It is the metal piece in this picture below

AScarlett08

That appears to maybe be a component on a newer model truck or larger engine. I have a 1999 Ford F-150 with the 4.2L V6 motor

Southernhunter9

Mine did that because I didn't change the o-ring on that metal peice that comes out the top of the water pump.

bill06447

x2 I always put a touch of sealant on the pipe before squashing it in the hole. Otherwise they leak on me.