sdgraham Posted August 17, 2011 Report Share Posted August 17, 2011 Whereever the car is in idle, water backs out through the cap on the coolant tank. Even when i turn the car off. It usually empties out the coolant tank. Link to comment Share on other sites More sharing options...
BodybyFisher Posted August 17, 2011 Report Share Posted August 17, 2011 Is the cap new? Is the coolant concentration at least 50/50%, has pure water ever been used? Has the thermostat been changed? Is the water pump belt good? Does the system have any leaks?, does it hold pressure (does the upper hose get hard?) Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Ranger Posted August 18, 2011 Report Share Posted August 18, 2011 Another '99! Is it overheating when you drive it? Link to comment Share on other sites More sharing options...
sdgraham Posted August 18, 2011 Author Report Share Posted August 18, 2011 Is the cap new? Is the coolant concentration at least 50/50%, has pure water ever been used? Has the thermostat been changed? Is the water pump belt good? Does the system have any leaks?, does it hold pressure (does the upper hose get hard?) The cap is not new pure water has been used water pump belt is good does not have any leaks upper hose does get hard the water concentration bubbles out of the expansion tank whenever car is at idle or turned off after being driven. Link to comment Share on other sites More sharing options...
sdgraham Posted August 18, 2011 Author Report Share Posted August 18, 2011 Another '99! Is it overheating when you drive it? It does not overheat when i drive. Gauge usually stays at 12:00. Link to comment Share on other sites More sharing options...
BodybyFisher Posted August 18, 2011 Report Share Posted August 18, 2011 Straight water boils at a lower temperature than water with a 50/50 mix of coolant. Coolant raises the boiling point and drops the freezing point. PRESSURE raises the boiling point. Lets assume that your system is holding pressure since the upper hose gets hard, but if your cap is old, replace it with an OEM cap. The system MUST hold pressure at 15 to 18 PSI to suppress boiling with a 50/50 mix. When the car sits after being driven the temp increases greatly and it will spontaineously boil if it does not hold pressure or the coolant concentration is low (like you have done with adding water). I have seen temps around 245 after I turn off the engine, straight water will boil, especially if the system is not holding 16 to 18 psi. I believe that is what you are seeing. The correct thing to do would be to have your cooling system pressure tested by a good radiator shop to see that it holds pressure to determine if your system has any leaks. If your system is only capable of holding 10 psi, you will see these types of problems. The CAP must also hold pressure, caps go bad. You need to add coolant to bring the mix to at least 50/50 and you could bring it up to 60/40 in hot conditions, but the water has to go. Keep in mind that you will NOT be able to get the remaining straight water out of your engine, so your new coolant mix needs to consider that. I would mix the new coolant at 60/40 to compensate for the water in the engine. You are going to need to dump all water out of the system from the low point in the cooling system, to get as much water out as possible. Buy a coolant test gage to test the coolant when you are done balancing the system. When was the thermostat replaced now would be a good time to do that since you are dumping the water Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Ranger Posted August 19, 2011 Report Share Posted August 19, 2011 Another '99! Is it overheating when you drive it? It does not overheat when i drive. Gauge usually stays at 12:00. It is not overheating, but still overflowing coolant? Does this happen when the engine is cold or just after it is hot? Is the gauge still at 12:00 when it overflows? Link to comment Share on other sites More sharing options...
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