over heating and no heat in car

[big sven]

1992 cadillac deville has new water pump and thermostat we had heat for a few days but then it went away now my coolant temp lite comes on and i get no heat from the heater. no visible signs of leakage or puddles when parked. no coolant in the oil and will not pull from the resevoir will add to resevoir it seems. what could be the problem is there a sensor or vacumm vale acting up is the heater core plugged ???????
please advise if can
. thanks big sven

[caddydaddy]

Check the coolant line that runs from the radiator (right below the cap) to the overflow tank. If that gets plugged up, it can cause the coolant to go into the tank, but not fill the radiator back up when it cools.
I had this problem on my '94 Deville 4.9 a year ago. There was gunk plugging that vent line right under the radiator cap. I could see it when I took the radiator cap off.

[DFBonnett]

Assuming the coolant level is OK, I'd suspect a defective thermostat. With the engine running, are both the upper and lower hoses hot? How about the hoses to the heater core?

[caddydaddy]

Originally Posted by DFBonnett

Assuming the coolant level is OK, I'd suspect a defective thermostat. With the engine running, are both the upper and lower hoses hot? How about the hoses to the heater core?

Except he stated it adds the coolant to the resevoir, but does not pull it back to the radiator. That's the sign of a clog!

When it did this to my car, there was a lot of air caught in the radiator, causing the overheat. My guess is there is also little or no coolant in the heater core, and that explains why the car has no heat as well.