Big radiator tube shrinks when switching modes on heater from vent to defrost


Asked by Sep 21, 2014 at 06:36 AM about the 1990 Lincoln Town Car Base

Question type: Maintenance & Repair

Refreshing coolant after heater core replacement. Add 1,5 gallon of distilled water in
radiator to flash to remove residues of old coolant. Put heater on max in mode "vent".
Start engine. Then after 10-15 minutes of engine idling, I've turned heater mode from
"vent" to "defrost' and upper radiator tube shrinks extremely and engine sound is
changing. Coolant temperature is always in normal. And bubbles always coming out in
coolant reservoir. By the way one of heater core tubes that goes "in" is hard and hot,
but other tube that goes "out" is quite soft. Any versions? Thank You!

4 Answers


But hose and termostat are new

took that down just as you posted because I got to -re'thinking it, and not so sure of myself, Your statement proves it, I was wrong. so.. the hose collapsing is from when radiator dumps coolant in to overflow and creates a vacuum. Maybe a new radiator cap, could be that simple because since it's not overheating the cap should hold the pressure and not dump in to overflow tank

2 of 2 people found this helpful.
Best Answer Mark helpful

As far as the part about the heater core hoses, the one going in is pressurized and hot, but after passing through core, which is just a small radiator, it's cooler and not as much pressure

2 of 2 people found this helpful.

Sounds like you possibly have some air trapped in the cooling system.

2 of 2 people found this helpful.

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