hissing and steam!

[OldsJax]

Hello All! A few months ago I bought an 01 GLS with the 3.4 (I guess all GLS models are) and while it doesn't overheat it usually runs either a smudge below halfway on the temp gage or a little above (not true accurate readings, I know).

I have noticed that when the AC or Heat is on it will typically run at a lower temp but when the ac system is off it will increase especially at idle.

The issue: I was at a stoplight the other day after the car had only been running about 15 minutes or so and the temp gage was just around half when I heard a loud hissing noise like a pressure cooker and saw white smoke or steam billowing out from the front of the car. I drove home with the heat on the rest of the way (20 miles city traffic) and it stayed below half. There were no leaks or loss of coolant.

Yesterday I replaced the water pump, fuel pressure regulator (was getting that fuel smell) and PCV valve and hose (casualties during regulator being replaced). I drove the car today about 20 miles and was fine with the heat on but noticed a weird noise at one point like a gurgling while idling.

I tried to burp the system using a spill proof funnel (lisle brand) with the heat off, about 5 minutes of idling and the temp still below half (was about 50 degrees F in Florida today) I hear the hissing and steam coming out again. It seems like it's in the lower part of the engine or possibly under.

Are there any ideas on where I should look next? Should I try burping the system again with the ac/heat on? I've also heard of possible similar issues with a heater hose. I'm just hoping it's not the radiator or head gasket.

Thanks and sorry for the super long first (2nd) post!

[01OhioAlero]

Could it be the quick dis connect leaking on one of the heater lines, going towards firewall? Mine was and hit the rear exhaust manifold and made steam and hissing sound.

[shinnick66]

I flushed my coolant a few weeks ago. I went to run just water for the 3rd flush and filled the system from the cap hole and my system was all messed up, temp started climbing and it was gurgling and I burped it from the valve. When I put coolant back in it I fill the radiator from the upper hose, then filled the motor through the heater core from a heater hose. Covered the ends with my hands and got them on without much coming back out. Topped of the tank, bled the valve with the cap off till I felt warm water then bled it with the heater on. Long post I know. Maybe it helps? My car runs just under 1/2 unless I'm in traffic then it goes over 1/2. Not over 3/4. In the summer though a/c on and climbing it will get over 3/4 tell I stop climb or turn the a/c off drops quick with the heater on.

[OldsJax]

Thanks for the replies, I'll check out these suggestions. I forgot to add, that when the hissing and steam start if I turn the car off it immediately stops almost as if it's high pressure steam leaking out from somewhere.

[Garfield]

When I had steam start coming from under the hood on my car it was the quick connects on the heater core hoses. (Mine was leaking on the block side.)

I just popped the hood with the car still idling and looked for where it was dripping/steaming.

[OldsJax]

Thanks, I'll pick up a couple and replace them, looks like there's two hoses coming from the heater core with them back there.

Are the hoses and connectors from the heater core under more pressure when the heat/ac is off? Both times I've had it steam on me the system is off but with the head/ac on I've been able to drive it for trips up to 25 miles with no issues.

[zzyzzx]

Can't you just remove the crappy plastic connectors on those hoses and clam them on like it should have been from the factory? Should I do this as PM?