I am working on my sister's 2003 Mercury Grand Marquis 4.6L. I just finished replacing the intake manifold due to broken plastic next to a gasket below the thermostat housing. The thermostat seal was split in multiple places, and I thought that was the problem originally. I want to clarify the car had no interior heat prior to any repairs, and still doesn't. Now there is a new manifold, new thermostat, and seal. The coolant reservoir is full, and the car warms up quickly (normal), much faster than before with a bad seal. The engine never got hot (above normal operating temp) before, and still doesn't. There are no coolant leaks after replacing the manifold, and no leaks from the cap.
I am not dumb, I do this with caution (and don't recommend anyone else doing this), but with the car fully warmed and still running I can remove the coolant cap. By remove I mean remove it quickly, because there is almost zero pressure built up.
Here are my thoughts, but please give yours. I think there can only be 3 possibilities.
1- Bad cap. I think this is likely.
2- A clog somewhere. Maybe...
3- Bad water pump. I don't think this is the case. If this is, shouldn't it overheat?
I don't think it's the heater core, but I'm not 100% positive. No, there is no coolant in the lines going to and from, but both are very hot. If there was a clog in the heater core, one hose should be colder, right? And if it's leaking, it would wet the passenger floorboard, and that's not happening.
Thanks in advance for any advice and help!
I am not dumb, I do this with caution (and don't recommend anyone else doing this), but with the car fully warmed and still running I can remove the coolant cap. By remove I mean remove it quickly, because there is almost zero pressure built up.
Here are my thoughts, but please give yours. I think there can only be 3 possibilities.
1- Bad cap. I think this is likely.
2- A clog somewhere. Maybe...
3- Bad water pump. I don't think this is the case. If this is, shouldn't it overheat?
I don't think it's the heater core, but I'm not 100% positive. No, there is no coolant in the lines going to and from, but both are very hot. If there was a clog in the heater core, one hose should be colder, right? And if it's leaking, it would wet the passenger floorboard, and that's not happening.
Thanks in advance for any advice and help!