bw_hunter

Thanks Injuneer...I keep forgetting the OBD2 cars can be different....

Fatdog2

I know the radiator has to be drained a bit to install the sensor,and after you refilled the radiator,and ran the engine,did you check the coolant level at the cap when the engine got cold again.Also bleed the 2 air screws for air.When I flushed my radiator(took several days draining,filling,draining,filling)with distilled water.Then did the 50/50 coolant.Shoebox has a easier way but this worked for me.I also had the heater on all the time as the flushing/coolant thing has to go through the whole system.I bled the system each time.But every day in the morning when I went to check the cap I had to add a little coolant.My coolant reservoir was level was up there but dirty,so I blew air through the hose from the radiator cap area to the reservoir till I could hear bubbling.Then I sucked out all the bad rusty stuff out of the reservoir,refilled it,sucked out the old several times till clean.After all was said and done,I was adding coolant(maybe a thimble amount)every day for 2 weeks.Been great for 1-2 years now and no more coolant light.Hope this helps.Sorry for the long post but that's what worked for me.

zootzee

Thanks guys for the input. I did bleed the screws when I started it back up there seemed to be no air in the system. Today when I opened the hood the top rad hose is collapsed a bit and the coolent level down in the rad.
Off to get some more coolent. I guess I'll add, run, bleed the system until it's steadily full.

Appreciate all all the feed back.

Injuneer

You might want to check the radiator cap. Sounds like as the radiator cooled down, the vacuum relief in the cap didn't open to allow the vacuum in the radiator to pull displaced coolant back into the radiator from the reservoir. That might explain the collapsed hose, and the low level.

zootzee

Oh Reslly???

When yiu you say check the radiator cap,, is there a way to check it. Or do you mean just buy a new cap??

I was curious about the water not being brought in from the reservoir seeing how there was suffice coolent in there.

Thanks for the input.

Injuneer

You can check the cap with a radiator pressure tester. A decent auto parts store ought to be able to do that for you. You want to be sure the cap holds 18 PSI on the pressure side, and opens under vacuum.

Not an expensive item.

You can also have problems with coolant not going back into the radiator if the rubber hose from the reservoir to the radiator is cracked, or the metal tube it connects to (under the battery) is corroded and leaking.

zootzee

Ok thanks for the help

Fatdog2

Absolutely a must do.I forgot about the cap.The mechanic I used before I did this right put a new stant cap on,but I replaced it with a genuine GM cap at the same time.