Gurgling heater core

Today, I changed the thermostat in my fiancee's 1997 SL2. It had not been running up to temp, vents only blowing mildly lukewarm air after running for half an hour, poor fuel economy etc etc. It now runs great, idles better, warms right up, and blows heat hot enough to make you seriously uncomfortable.

Only one problem arose. She had also been complaining of a sound that sounded like water sloshing around behind the dash. I checked the drains for the windshield wiper housing area, as that's usually what causes this noise, but it was not full of water and the drains were clear. I started poking around after I replaced the t-stat because the sound grew even louder, and it turns out it's coming from the heater core, like there's an air bubble or there's some shearing of the liquid on the way in and out. It is most noticeable upon acceleration, when I assume the water pump is pushing the most liquid through the system.

Now, the car runs fine. The vents blow hot air. The top coolant hose gets hot and the bottom stays ambient temp. It is otherwise a perfectly functioning cooling system. Is it worth it to fool around with this? Maybe there's a bleed screw on the heater core that I could vent the air out of?

The system as a whole still has some air to bleed out. Give it another bleed at whatever the highest bleed point is, even if you have to pull a small coolant line or something if there is no good bleed point, and get the last of the air out of the system. I don't think there will be a specific heater core bleeder, but as I've never played with a Saturn, I could be wrong.

Ditto, there is still air in the system and it needs more bleeding.

Air.

Let it run for 40 minutes in the driveway with the heater wide open.
Check fluids and leaks often.

The last thing you want is hot, steamy socks.

Dan

Try elevating the nose while you've got it idling in the driveway as well. Sometimes this helps to dislodge stubborn air pockets.

GM has had more than a few complaints about that. Dunno about the Saturns, but the N bodies (Skylark, etc) had a bulletin where a restrictor was added to the outlet side of the core to shut up gurgling noises. It was a cylindrical piece of what looked like zinc with a hole drilled in it, You removed the hose, stuck the restrictor in, then reinstalled the hose. If the heater hoses have been replaced, someone may very well have tossed the restrictor as well.

I had a Yukon (1995) that did that. Sounded like the last bit of water going down the drain (or toilet). A couple of attempts to get the air out of the system solved the problem.

Alright. The only access point to the cooling system is the overflow tank, which also becomes pressurized when the engine is running. Should I crack the cap slightly and run the car for a while to get the air out? I was under the impression that would ruin the water pump.

Twin_Cam wrote: Alright. The only access point to the cooling system is the overflow tank, which also becomes pressurized when the engine is running. Should I crack the cap slightly and run the car for a while to get the air out? I was under the impression that would ruin the water pump.

Really? I've never heard that one. Ruin the water pump by running with the pressure cap loose? Hmm.

On a Miata, it helps to elevate the front of the car to get the radiator cap above the engine. On a MINI, there is a separate bleed port that must be opened to let the air out of the top of the system. YMMV of course.

leave the cap off entirely and run the system. just keep adding coolant until it stays at the correct level and the car is at operating temp.

Ok, cool. I'll try it.

I assumed that running the system would burn the pump out. At work, when we use pumps to move beer or chemicals around and from tank to tank, running a pump with no back pressure after the outlet is bad news. It'll make the pump cavitate, i.e. ruin the seals completely.

Water pumps on an engine are not displacement type pumps, so running with no pressure won't hurt them. The bearings are sealed with grease in them, like an alternator bearing so that wouldn't be a problem. Running dry could possibly damage the spring loaded seal, but I'm thinking the engine will probably have much worse problems before the seal gives up.