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coolant loss but no internal leakage

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.

Reply to
phil
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Could be air in the system- there might be a coolant bleeder somewhere, or a certain hose you need to pull to get all the air out.

When cool, pull the radiator cap and fill the system if its not full. Make sure the radiator cap is in good shape, or just replace it.

Dave

Reply to
spamTHISbrp

Yeah, the uppermost heater hose is a good place to help bleed this system. They can really suck to get the air pocket fully removed if you don't do this.

Toyota MDT in MO

Reply to
Comboverfish

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