1999 Cadillac Deville over heating

Tiny
JGILLES
  • MEMBER
  • 1999 CADILLAC DEVILLE
  • 160,000 MILES
Radiator had a crack by the top hose so I replaced the radiator. I filled it up turned it on and it started overheating again. Both top and bottom hoses were very tight after it warmed up. The thermostat is good so I figured it was the water pump. I tried to take the water pump out but it is rusted in place. Does anyone have any suggestions or solutions for this problem?
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Friday, August 23rd, 2013 AT 10:55 PM

5 Replies

Tiny
CARADIODOC
  • EXPERT
The water pump is the last thing to suspect. Chances are there's an air pocket under the thermostat that needs to be burped out. Thermostats don't open in response to hot air, just hot liquid. Look for a bleeder screw or plug near the thermostat housing. If there isn't anything, look for a sensor that can be unscrewed, then refill the coolant.
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Friday, August 23rd, 2013 AT 11:16 PM
Tiny
JGILLES
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I also removed the thermostat. I didn't see a bleeder screw or plug but will look tomorrow. Thanks
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Friday, August 23rd, 2013 AT 11:24 PM
Tiny
JGILLES
  • MEMBER
Couldn't find a bleeder screw of sensor that can be unscrewed around the thermostat. I bypassed the heater core and the thermostat is removed. Both hoses are tight when radiator cap is on. Water starts to boil in overflow when the car gets hot. After I turn the car off and remove the radiator cap the water shoots out as if it is under a lot of pressure.
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Saturday, August 24th, 2013 AT 1:33 PM
Tiny
CARADIODOC
  • EXPERT
The next thing to consider is a leaking cylinder head gasket. That will put combustion gases into the cooling system under higher pressure than normal, and the air can cause a thermostat to fail to open. Your mechanic can do a chemical test at the reservoir. That involves drawing air from the cooling system through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present that liquid will turn bright yellow.
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Saturday, August 24th, 2013 AT 1:57 PM
Tiny
JGILLES
  • MEMBER
I guess that could be the reason for the recent random misfires.
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Saturday, August 24th, 2013 AT 5:00 PM

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