I have a 97 crown vic. 4.6l
3 mos ago, the intake manifold was replaced--old one split
about month and 1/2 ago, I notice that the coolant expansion tank was dry. I have been adding coolant ever since.
I pressure checked the system. the needle holds steady.
No external leakage of coolant noted. water pump was replaced about 5 mos. ago.
notice from time to time, that the heater will blow cold. the temp gauge will climb, then fall back down--heat then felt coming from vents. still happens even after replacing thermostat.
I'm stumped. If the head gasket were failing, or if I had a crack in the block, then I would have seen a loss of pressure when I pressure checked the cooling system.