I have an LDK in my 09 ss. It was installed by the dealer in Nov 2018. It had cooling issues, the temp was bouncing around but no check engine light so i just drove it. It never blew up, it stayed cool and made boost. This year the cold weather moved in and i noticed my temps are all jacked up. New LDK from ZZP came with all new sensors and tstat so i was confused. First i thought there was air in the system. I called my Dad, a GM Tech. he said it sounds like the tstat is bad. So i replaced the tstat 2 weeks ago and same thing, sh**. Tonight we made it happen. I called popps again told him whats happening, my lower hose was ice cold, one fan is hot, the other is cold. Obviously its air. I tried to make it move by hand, but that was not working. He mentioned putting a coolant pressure tester on while hot. I would recommend if you're low add some coolant before doing this. If you're starting from cold, when the upper hose starts to warm up hold your lower radiator hose shut by hand to build pressure in the system to help the flow. When you feel the lower hose start to warm up hook up the pressure tester cap for your tank and wait till it gets up to temp where fans kick on. When fans come on connect pump and pump it 17 psi and let sit, it will drop, try to keep at 17 psi. This will help aid the pressured system push the air out and force the tstat open so when hot The fluid level should go down a bit or how ever much you need. keep track and dont let it get empty. Keep the process going until both fans come on and both blow hot and you should be good. These motors are known for this problem air gets trapped in the head. Hope this helps anyone with cold lower hoses or overheat after installing cooling parts.

 

Next time you do coolant work I would use a vacuum bleeder, pulls the entire cooling system into a vacuum and you fill it, no bleeding necessary, collapses every hose flat and gets to both sides of the thermostat

 

The dealer did it and thats what they did and it still had air.

 

Aren't you supposed to fill the coolant tank and radiator and then the top hose, then reattach the top hose to the radiator?

 

Thats what is weird, some places list to fill the radiator thru the hose (unhook from engine side), some say fill engine (unhook from rad side). I believe pull the hose off the rad and fill the engine is the correct way?

 

<This> from what I've read on here & have done. Pull upper radiator hose from radiator & fill engine. When full reconnect hose & continue to fill through expansion tank until it's @ the cold fill level turn on with heater running. Watch coolant & fill further if necessary. Also helps to Jack the front of the car way up. I didn't do it this way when swapped radiators & had problems as well. Jacked up the car really high in the front & had heater running with no heat. Car temp went up to 235° f & finally started to stabilize stayed @ 225° for like 30 minutes. Finally started getting warm air.