Lincoln LS No Heat at Idle

[Happster]

Had the standard degas bottle issue with an LS, but the prior owner ran it for 50 miles with little to no coolant and the fail-safe system did not kick in because the temp switch was broken clean off. I fixed the temp switch and replaced the degas bottle and thermostat. No signs of head warpage, cracking or blown head gasket (not losing coolant, runs fine, oil is clean, exhaust is clean). I filled the system and followed the air bleeding sequence from the Ford service manual to a "T". Yet, the heat only works when I revv the engine to 2000 rpms for a few minutes. Once I'm back to idle, no heat. Doesn't appear to be any heat under normal operating conditions either. Sounds like low coolant, air in the system or both, but the degas bottle is at the right level after two driving and cooling sequences and I've done all the manual says to do to bleed the air out of the system. Any help?

[shorod]

You're right, that does sound like air in the system.

You probably need to check the oil/dipstick to make sure there is no evidence of coolant in the oil. Beyond that, you're probably going to need to check the heater hoses at idle to see if the heater hoses to the DCCV remain warm, even if the outlets from the DCCV to the heater cores do not get hot.

-Rod

[clubairth]

This is the classic symptoms of a bad Aux coolant pump. It's located under the DCCV on the passenger side of the engine. It's a bit hard to change because of where it's at. Pump should be in the $100-150 range.
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