Question about 2002 Cadillac Sts

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Engine hot noticed heater not heating...then engine hot message came on

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The most common overheating problem with the Northstar engine is a blocked purge line. It's job is to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.The hose goes in to the engine to a crossover and comes out the other side to near the thermostat housing,the blockage may be there.
Remember also,on the Northstar engine,the thermostat is located at the bottom hose,not the top as in conventional cooling systems.

Posted on Jan 28, 2010

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First of all you need to check your coolant return bottle level, it's probably low, and needs coolant added. Heater will be starved for coolant, if level is low, thus, cool/cold air comes out. Try to add when engine is cool, to avoid getting sprayed with hot coolant. Leave cap off for a while, turn your heater on (not defrost) and let engine run up to temperature, and add more as needed while you watch level. Rev engine slightly and hold it for 5 seconds or so, every once in a while to help circulate coolant, and remove any air in system. If you have an actual rad cap, that you can remove and watch flow in radiator, that's even better, for adding and bleeding air out same way. Make sure your rad fan is working as well, and once you get it topped up, and heat back working, I'd seriously consider having a system pressure test done, as you obviously have a leak somewhere if the level went down to the point of overheating, and heater was starved for coolant. Keep an eye on that return bottle level until such time you have it checked, to avoid more damage to engine.

Posted on Dec 12, 2009


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