zztopo

Ok so its 102*F. outside. So of course I'm using my AC. I made couple of errands, and as I pulled into my parking lot, the HID says "Engine Overheating." I look a my water temp gauge as it is fully pegged down and to the right.

This seemed to happen instantaneously, but I wasn't checking the gauges since I have never had this problem before, so it could have been building up. Also, my AC stopped blowing cold air at the same time.

After 45 minutes, I went to check on it, and it read 220.

Water pump?

Napoleon_Tanerite

Well, step one, is it ACTUALLY overheating? The DIC warnings depend on the readings from the sensor on the driver's side cylinder head. In those ambient temperatures it certainly is possible that the car is overheating due to the C5's hot blooded nature, but it's important to ensure that you actually have a problem beyond a faulty sensor.

When it indicates an overheat condition, lift the hood and check the coolant overflow tank. DO NOT OPEN THE CAP!!!!!! Look for signs of boiling coolant (such as bubbles in the tank) or if coolant is overflowing around the cap via the pressure release mechanism. If that's the case, you are indeed overheating.

If you're overheating, there are a few quick steps to take.

1. Ensure all body work is in place and in good shape, ESPECIALLY the front air dam in the center under the front bumper. That dam channels air up and into the radiator
2. Ensure that your fans are running when indicated coolant temperatures are above 225F
3. Check for excessive dirt or debris in the radiator and between the radiator and AC condenser. Clean this area well to ensure good airflow

If those three steps are all in good order, NOW you can start looking for issues with the cooling system such as a bad thermostat, collapsing hose, or bad water pump

zztopo

Thank you very much. I was hoping for a "false alarm," but it is real. I just took it for a quick spin without the AC on, and it stayed at 218F* F. What a shitty time for the engine and AC to hate each other; we're breaking heat records with no end in sight! I guess I'll be sweating my *** off until I do what you suggested. I don't have $ for a new water pump. Question: I want to change to 160* stat. I don't like my engines running that warm in this goddamn heat. Good idea?

Again, thank you for responding.

Napoleon_Tanerite

So it's only overheating with the AC on? This makes sense since the AC condenser is in front of the radiator and serves to heat the airflow that ends up in the radiator, but still shouldn't lead to such a drastic difference. Are both sides of your AC blowing cold? It might be worth it to check the pressures in your AC system. Also did you check to ensure that the air pathway is clear to and through your condenser and radiator?

And a 160 thermostat won't do much to help. Operating temperature for the cooling system is higher than that anyway, so once the system is up to normal temp the thermostat will be open either way.

Get an IR thermometer and check the temperature of your radiator hoses. You should have a temperature differential (referred to as "delta T") between the two hoses of ~15-20 degrees.

gimp

Step 1: Get the car in the air. Use compressed air to blast, rear-to-front, all the crud out of your radiator and condenser. A fistful of dirt is enough to bring temps up 20-25F on a hot day, and two fistfuls is enough to overheat the engine.

jim993

Has there been any work on the cooling system recently? What is the coolant level?

zztopo

Good plan. The car goes in to the shop next Wednesday to do the anti venom mod. I live in an apt. and I have no garage. Plus my ex-roommate stole all my tools, compressor and all.

Do you think it is actually a good sign that the engine only overheats when the AC is on? I cannot afford a new water pump anytime soon.

Napoleon_Tanerite

Tough to say whether it's a "good" sign or not. Getting everything clean is a big step in diagnosis.

Another thing that you can do is to go to the HVAC section of the hardware store and get a can or two of coil cleaner. It will come in an aerosol spray can. It sprays on as a foam and helps clean up the radiator and condenser without any kind of harsh chemicals or abrasives that could damage the delicate surfaces. When you rinse everything out don't use high pressure, just the flow from the hose. High pressure water could be enough to bend the delicate fins and exacerbate the cooling issues.

zztopo

I have limited history of this C5. I bought it off a private seller, and he was pretty cool, but he did not give me much information. I've only had the car for 3-4 months now. I barely drove her and put a good car cover over it. I have a 4Runner that was my daily driver, but some douche sidewiped me and the car is undriveable. So I have to drive the C5 as my DD.

About 2 months ago, I had a reputable shop do a thorough check. I asked about all the fluids and the tech said everything looked good. They did have to charge the AC system though, because there was no refrigerant left. Then it worked great!
I'll find out more next Wednesday, until then, I'll have to sweat my *** off or stay home. It's over 100*F. here and humid as hell. The forecast calls for things to get hotter.

Napoleon_Tanerite

Charging the AC system is a bit of a concern. Refrigerant doesn't just evaporate or is consumed. If the system was out of refrigerant that means it went somewhere, i.e. a leak. Being low on refrigerant could be why your condenser is running hot. Still clean everything up, but at this point I'm thinking the problem is your AC system, not your cooling system.

zztopo

Ok thank you!

zztopo

That makes total sense. Again, thanks.

helga203

Well if u have a targo. That is nice cheap A/C fix that u can do for the meantime. C5 are known for heating issues even if there is no problem found. But then some dont have any issues. Looks like u got the good one. maybe u will get lucky and the high speed fan relay is burnt out. Cheap fix for these cars. Somewhere around 800 or 900 buck and 200 to install. GRINDER 11 is a sponsor on here he is the cheapest around.

zztopo

I will certainly keep that in mind! I had saved up $ to have my nitrous system installed, but this may be delayed and the money spent on a healthy engine/AC first. I just made a long trip in stop-n-go traffic. The temp only went to 215*F. on another 100 degree day. But that was with the AC OFF.

C5MSG2004Vert

Two things. The anti venom mod is easy to do so save that money and do it yourself when you get the tools. Is it over heating with ac on when driving at 50mph? With the car hot and the ac on, are both fans running at high speed?

Vetteman Jack

Moved to C5 Tech.

zztopo

Thank you, sorry!

MWWarlord

I agree with the advice you've been given. Start by cleaning everything really well. Also, If you haven't already. make sure you haven't sucked up a shopping bag or something like that. The fact that your coolant needed to be recharged is definitely an issue. It's a closed system. That means that you either have a leak, or someone bled the system for some reason. As stated, a new thermostat will do absolutely nothing. If you want to make an aftermarket cooling modification, I would start with a tune that will have your fans turn on at a lower temp. Mine are set to come on at 199 degrees. The next cooling mod would be a Dewitts radiator (they run around $800.00 though). Keep in mind though that it is normal for an unmodified C5 to get as hot as 230 in stop and go traffic on a hot day. It won't hurt anything. Anything above that is a problem though. Good luck.

zztopo

Thank you everybody! This is my 1st Vette, so obviously I'm a newb. I have an appt. with my favorite car shop next Wednesday, so I'll have them do the anti venom mod and check the AC at the same time. I know the mod is simple, but my claustrophobia makes it hard for me to get under a car unless it's on a lift. So I am ok with paying for the install.

As far as the fans running, how can I tell? (Newb question). I live in a dense retail commercial area, so I don't get over 50 mph often. But I'll hit I-65 and give it a try.

gimp

Pull off to a parking lot, pop the hood, check to see if they are spinning. Or listen for the sound of them turning on. Some people even wire a light into the circuit, though I wouldn't recommend doing that unless you know exactly how.