I've noticed that the overflow tank has been boiling when I turn off the engine (I can hear it IN the car!). Obviously, something in the cooling system is not working as it should. The coolant level is a decent green, and if anything, a little too HIGH. I recently had a problem with the system and had the cap and a thermostat replaced because they'd been shot by prior high temperatures. Oddly, the temp gauge only rises above normal levels on short trips and when idling for long periods. (see next paragraph)

I don't know if it could be related, but I've had a loooong history of A/C problems, and I still have A/C problems on short trips (minimal cooling, if any, in parked, idling position). Perhaps the engine is getting too warm to properly allow for cooling?

At any rate, I'm concerned about the boiling first. Can someone please suggest and/or list possible causes? I'm just SURE that it's going to be something BIG! But, I'm reasonably handy, so if it's something I can do or replace myself, I'll gladly save myself the trip to the expensive shop.

Thanks for all responses!

 

make sure that the radiator fan works
be sure that you have atleast a half gallon to a gallon of antifreeze in the cooling system along with the water
also check your belts and water pump. if you have a bad belt (or a missing belt) it could cause the water pump not to be moved

if all else fails, when you get home, on occasion that you would notice the boiling, dont shut the car off but instead pop the hood and investigate possible causes while its running (ie: fan or water pump)

as for the AC issue, you might just need to have the freon recharged

the only thing i could think of that comes back and relates to everything would be a bad or under-tensioned serpentine belt system (if you have it)

 

Could also be that the new thermostat was put in backwards. That will result in overheating. Likewise, a collapsed radiator hose can cut off coolant flow. If it's collapsed on the inside, it may not be readily apparent.
Check for leaves and crud on the radiator. That could also affect A/C performance.
Worst case, a blown hwead gasket. Rule out all the other stuff first.

 

Seems like great advice from both of you - thanks very much!

 

One vote for a blown head gasket.

 

The previous problem in the cooling system, the one that caused you to replace the thermo and cap, could definitely be caused by a faulty electric fan. Both overheating and a/c problems are symptoms of fan failure. See, the fan pulls air throught the radiator at high temps, such as when you are stopped or in slow traffic. At high speeds, the air is forced through the a/c and then the radiator, along with any transmission cooling grids. Check your fan and then check the thermo and cap. 50/50 mix of antifreeze is suitable in most of the country. Too much coolant and the temps will be higher, too little and you run the risk of freezing. If the coolant has boiled, you will need to re-adjust the mix. Oh, running the heater on high will help control the overheating problem, as long as you can stand it...

 

Thanks again for all this advice! Here's an update:

First, I see I did not specify that this car is a 2000 Cirrus LX, 2.4L engine. (whoops) Don't know if that's even important to know, but it can't hurt.

From reading online info for about an hour on blown head gasket symptoms, I don't think that's my case. I have no coolant loss whatsoever (except perhaps some in boil-off), and the engine seems to be performing just as it always has. At first I though, "Heyyy... this could explain my slow loss of oil...", but upon closer inspection of the engine area, I see the affected spot, indicated by its black, shiny appearance - more on this in a moment.

Yesterday, I popped the hood, inspected every hose I could find for cracking, bulging, collapses - anything that didn't look normal. Nothing. I removed the radiator cap... there was the normal, green coolant color there, but the inside of the cap itself was coated with a muddy-rust colored slime. (?!) I put it back on and started the car up with the A/C completely off. This car has dual fans behind the radiator grill, one passenger side, one driver. Neither fan turned on start-up. I then cranked the A/C to 4 (of "Off, 1, 2, 3, and 4" settings) and both fans fired up. I inspected their movement closely with a flashlight. The passenger fan looked strong and steady, but the driver fan, though turning, seemed slightly slower and a little wobbly on its axis. I turned the A/C to 1, only the driver's fan stopped. Checked at 2 and 3, no change... driver's fan still off. Hm. Back to full 4 and it STILL didn't kick on again. I can't help but wonder if I'm losing this fan's full function. Granted, it was maybe in the high 70's at the moment (cool for Florida), so I don't know if it KNEW it didn't need to come on yet for cooling.

At any rate, I replaced the radiator cap with a Stant safety release cap, in case it was a simple pressure leak from the old (well... 6 months old) one. I'm holding off replacing the (also 6 months old) thermostat, to see if the cap was the culprit. Seems like a lack of pressurization, coolant flow, or proper fan operation could explain the A/C issues as well as the boiling overflow.

Can anyone tell me what behavior I should expect from these radiator fans? Are they supposed to run together, or do they decide to come on individually, based on feedback from the cooling system?


As for the oil... it's a slow loss, occasional drips... about the time I'm ready for an oil change, it could use a quart. It seems to be dripping from something I'm not familiar with though. Straight ahead of the steering wheel, near the front of the car, almost directly under the battery, there is a square (slightly rounded corners) metal box, best seen from underneath. The box is about the size of a man's head. This is where the oil drips from. It is separate from the engine, so it doesn't seem likely that this part should even HAVE oil in it, so how could oil be getting to this part to drip off? It's quite covered in shiny, slimy black gold, so it's getting a good exposure from somewhere. I don't know this box's name or function. There is a sad shortage of labeled engine diagrams for this car, I've found out.

Thanks again to all who reply!

 

Specifically for this car, I'm not sure about the exact task of the fans at low coolant temperature or with the a/c switched on. Most cars, when the a/c is switched on, the coolant fans will come on full speed and serve two purposes:1. to get the full function of the a/c at low speeds or while stopped;2. to provide extra engine cooling due to the extra strain that the compressor puts on the motor.

I need to know what these fans are doing at full operating engine temperature with the a/c on, and off. We'll go from here, but initially it's sounds like a bad fan. Don't let her overheat again, if it starts to, crank the HEAT on high and rev the motor up to about 2k-rpm's until the temp is back down. Leave the heater on while shutting her down to prevent boil over.

 

Maybe someone more familiar with the engine bay on this car can help with your oil leak but I'm guessing and engine oil coolant line is probably to blame. Remember, only guessing on the leak...

 

You mention it only boils when turned off.....this is not boiling over it is just releiving the pressure within the cooling system. if the temp runs fine at idle and driving down the road it is working correctly.
When the engine is shut off, the temp rises and the cap is designed to release pressure at about 16psi. this would be considered normal.
happy motoring

Glenn beasley