View Full Version : filling coolant system after flush

01-04-04, 02:52 PM
I have a 1998 Aurora with the Northstar engine. I was wondering if you could help me out. I just flushed the coolant and wanted to know if there was a pressure release to loosen before filling the coolant tank or if I just pour it in? Thank you.

01-04-04, 03:23 PM
I have a 1998 Aurora ... I just flushed the coolant and wanted to know if there was a pressure release to loosen before filling the coolant tank or if I just pour it in? Thank you.
If I remember correctly, there isn't a manual coolant bleed port. In fact, if you look at the coolant recovery tank, you'll see a small diameter hose entering the top of it coming from either the top of the radiator or the coolant outlet near the thermostat. That is for allowing air to bleed itself to the recovery tank.

I do have a couple of hints, though. :yup:

First, make sure your coolant isn't the cheap stuff. While Dex-Cool isn't an absolute necessity, it does have it's advantages. If you're not using Dex-Cool, then make sure all traces of it have been flushed-out of the system. Equally important is to be sure that all traces of chemical flush have been removed.

Next, fill the system at the coolant recovery tank, and allow time for the added coolant to settle in the system. Air is removed mostly when properly filled, and whatever air is left gets forced out under pressure when the motor is running. (remember the bleed hose entering the top the recovery tank.)

When you believe there is enough coolant in the motor, (I believe your Aurora's capacity is around 10 quarts, I'm guessing), you can seal the system and start the motor. You'll need to visually watch for the level in the recovery tank dropping too much, and add more if necessary.

After a few minutes of supervised running, the motor should be almost warmed. It's normal for the cooling fans to come on prematurely when filling the system... don't worry unless the fans stay on and are only exhausting cold air on the engine-side of the fans. If that happens, you've got what is called 'air-lock'. Turn the motor off and investigate as to why the air pocket hasn't taken care of itself.

What you are looking for is the thermostat opening after no more than 5 minutes of engine operation, and the cooling fans cycling on and off.

Watch your coolant temperature gauge through the entire procedure. You do not want your engine (aluminum block and heads) overheating.

Stuck thermostats are common on high-mileage motors. Fortunately, most of them stick in the open position. You'll know if you've got a stuck-closed thermostat.

Always do the squeeze test on the upper radiator hose before opening the coolant recovery tank cap. If the hose is very stiff, be very careful.

::common disclaimer:: You are dealing wth something that, if you aren't careful, can either burn you or kill your engine. If you feel you're in over your head, get professional help. :lildevil:


01-04-04, 03:36 PM
Thank you very much. I have done other cooling systems but was not sure about this one. I had a ford diesel you had to loosen the upper hose on to get the air out while filling. I am using dexcool to refill it but do not have the seal pellets. I have been told that you need them and have been told that they only pollute the coolant. I have not decided whether to use them or not. Thanks again

01-04-04, 08:59 PM
I'd recommend them. The clogging/polluting story is from people who never maintained the system(changed coolant)til the had a problem. Then an additive gets blamed. Adding a small amount of sealant and changing coolant regularly should not cause any problems, it should eliminate them.

Aurora By Olds
01-04-04, 10:26 PM
Use the seal tabs, they DO work.
And dont worry about bleeding the system.
The recovery tank is the highest point in the system, so it will bleed itself eventually, unless you have a severe air lock for some reason.

01-04-04, 11:32 PM
Another very important but often overlooked point is......Use distilled water not tap water.

01-05-04, 02:39 PM
I have it done now and sealed up and it runs the right temperature. Should I be concerned about an air bubble in it or would it overheat if it had any air at all? Just wondering. Thanks