There are two things that may be going wrong with my truck. (1) when I…
Coolant is leaking from under passenger side exhaust manifold. I was wondering if it would be a hose or a freeze plug? It is a 1999 Ford F150 XL with a 4.2L V6.
How to Locate Coolant Leak
There are a few things to do in order to locate an external coolant leak. Fist top of the coolant level. I recommend using water since you will loose it on the ground anyway. Once the coolant is topped off you will need to put the cooling system under pressure. You will need a cooling system pressure tester for this. Take note of the max pressure on the radiator cap. Pump the pressure tester up to the max pressure you noted from the radiator cap. Look around the engine bay for the coolant spraying out. Now that you have spotted the coolant spraying out you know exactly where the leak is coming from.
Remove the cooling system pressure tester. Repair the leak. Once again top off the cooling system with water. Then connect the pressure tester and pump it up once more. It is good practice to check for additional leaks now before putting expensive fresh coolant back into the system. Once you see the pressure holding on the gauge of the tester go ahead and remove the tester. Drain the cooling system. Re-fill the cooling system with 50/50 mix. Run the engine with the radiator cap removed for a few minutes or long enough to top off the coolant level. Replace the radiator cap and test drive. It is a good idea to check the coolant level a few times over the next couple of days to ensure a proper level is maintained.