How to add coolant to radiator when recovery tank may be defective?

Asked by Dec 29, 2016 at 08:57 PM about the 2004 Cadillac DeVille Sedan FWD

Question type: Maintenance & Repair

2004 Cadillac Deville 4.6 Liter V8. DIC says "Check Coolant Level". There is
no heat from the cabin heater. All prior suggestions imply Coolant Level
Sensor is defective. My coolant reservoir is full. Car will overheat quickly, on
3 to 4 mile trip indicating very low coolant level in the radiator itself. I will
certainly replace the coolant tank and sensor. But it would be more
comfortable if I can determine that it is indeed defective. What test can I
perform that will provide proof that it is indeed the problem? What should the
sensor (Thermistor) resistance be to allow coolant to flow into the radiator?
Replacing the sensor requires replacing the tank of which it is a part, a $300
to $500 repair. To spend that amount because it MAY correct the problem
doesn't make sense without positive identification of the defect. Also, I find it
impossible to add coolant directly to the radiator. What procedure will enable
me to do so? Through the tubing connected to the recovery tank? Is air
pressure preventing coolant from flowing into the radiator? To have a vehicle
costing upwards of $50,000 when new to be made inoperable  because of a
single relatively inexpensive component that is designed so as to cost many
hundreds of dollars to be replaced is an inexcusable design flaw.

2 Answers


The coolant reservoir is under pressure, so any amount you add to that it will suck the coolant into the radiator once it is running. Is your cap cracked? Did you have a mechanic look the vehicle over to make sure it's not a coolant issue but maybe a blend door on the HVAC? But you mentioned it overheats. You might want to perform a cylinder pressure test as Cadillacs with the Northstar V8's are known for head gasket issues, which would contribute to the overheating.

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Best Answer Mark helpful

Pressure from a bad gasket pushing into the cooling system. The casting walls are too thin and gaskets fail. Like said before check compression leak down and test for exhaust in coolant test before replacing the tank & sensor.

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