Cooling Systemin 1999 Caddy DeVille.

Asked by Aug 05, 2014 at 01:06 PM about the 1999 Cadillac DeVille Concours Sedan FWD

Question type: Maintenance & Repair

My check coolant level warning is coming on.  I am not overheating but I need to add a gallon of coolant every 50 miles.  Had a pressure test done and all was O.K.  Radiator cap seal was bad so he replaced with a Motorad 16 radiator cap.  I'm still getting the warning every 50 miles and the last time I had to add 3 qts. of coolant.  Could the new radiator cap be the wrong one?

2 Answers


The most common cause is a bad thermostat. You can purchase a thermostat, gasket, and some blue rtv and do the job your self. After the car has cooled, locate the thermostat housing, remove the bolts and remove the housing. Remove the thermostat, and the old gasket. Be sure to clean the surface thoroughly. If the surface of the housing has corroded then that will need to be replaced as well. Assemble the termostat, gasket, and housing using the blue rtv. Allow it to cure for an hour at least. Add coolant and crank. Drive 30 miles, leave the car running, check all hoses, hose ends, around the thermostat housing and the water pump for signs of leaks. If you smell a sick sweet smell then antifreeze is leaking out and burning. If the tailpipe has that sickly sweet smell then you may have a warped head or blown head gasket.

1 of 1 people found this helpful.

Thank you, I will tell my mechanic what you said.

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