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2000 at 147k. Changed coolant, cleaned radiator & condenser last year. Confirmed both fans were working correctly. Most likely has stock tune. At ambient temperature of 75-80, it maxed out the temperature gauge after driving less than 5 minutes at 35 or less. I let it cool down to 183, then quickly got on the freeway. It got up to 230, then cooled down to ~200 & stayed for the rest of my trip, staying at 50 or above except for minute or two. On a 2nd trip, I got stuck at a couple of lights for 4-5 minutes & it again maxed out the temp gauge, then came back down as soon as I got up to 50.
Not sure where to start. I don’t see or smell coolant. Oil & coolant are clear & properly full. Was thinking about doing a flush in case of blockage. Maybe pressure being lost somewhere? Any suggestions? Thanks
Got this from a Bill Curlee post. HTHSitting at idle, with the a/c on, and in summer weather, your coolant temperature will cycle with the cooling fans switching between low and high speed. 235 degrees with a 50/50 coolant mix and a 15 or 18psi “radiator” cap is not over heating.
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
Do a quick look and inspect on the radiator opening under the front bumper. You would be AMAZED at what gets sucked up in there and blocks off the air.
One Forum member sucked up an empty 50 pound dog food bag which caused the engine to over heat!
- Look for leaves and trash in the air intake opening!
- Make sure that the fans are running (turn on the AC)!
- Check the coolant reservoir and make sure it properly filled.
- Check the cap and make sure that the system properly pressurizes. - You Should have firm pressurized hoses when the engine is fully warmed up!
- The hoses should NOT collapse when the engine cools down. = BAD CAP!
There is a 1" space between the radiator and the AC Condenser coil. That space is well known to get full of grass, trash, sand and dirt.
Remove the plastic cover that fits over the top of the radiator and take a look at that space.
Use a garden hose and back flush the radiator and condenser fins and flush out all the sand and dirt that gets trapped in the fins.
Thanks for the info. I did follow the procedure for burping the system after changing the coolant. My guess is that it would probably have showed up before now if that was the issue. I will follow the Bill Curlee suggestions & see what happens. Cheers!
Thanks for the info. I did follow the procedure for burping the system after changing the coolant. My guess is that it would probably have showed up before now if that was the issue. I will follow the Bill Curlee suggestions & see what happens. Cheers!
After reading your post again, I'm also questioning your T-stat. Was that changed last year, too? If not, I'm thinking you probably need a new T-stat.
While there are several potential problems when diagnosing overheating in a C5, I want to toss in my experience. YMMV. My 2003 wasn't so much overheating, but the engine temp was just all over the place, which I was uncomfortable with. I checked the usual things, including changing out to new antifreeze. One quick point here is that Dexcool is not compatible with some other types of antifreeze. Some people hate Dexcool, and I understand, but if you are not using Dexcool, you should flush all the old Dexcool out prior to changing to a different type antifreeze to be safe. Read about it. So when I checked for debris buildup, the first picture is the front of the condenser prior to cleaning. The second photo shows the area between the radiator and condenser. The third photo shows the front of the condenser after cleaning attempts. To get to the point, cleaning the radiator to improve cooling is not necessarily as easy as just blowing compressed air (carefully) or just back-flushing with a water hose. Especially look at the pic of the area between the radiator and condenser. Don't trust that back-flushing water through the radiator to clean the condenser is going to be very effective. Air has to go through the condenser to get to the radiator, so I'm going to stretch and say if you haven't removed the cover and back-flushed both the radiator and condenser seperately, you may still have debris blocking the air flow. Maybe if one cleans very frequently, this could maintain air flow, but once you get imbedded debris, back-flushing may not be as effective as you think. In my case, once I determined that debris was going to be difficult if not impossible to remove, I cut my losses and replaced both the condenser and radiator. I did go with a DeWitts radiator, and I am happy with that. I have rock solid cooling, but my problem was ultimately imbedded debris I was unable to clean out. One more bit of advice is that routine cleaning should occur more often in areas you live that may have more debris on the road. In my case, a rural area where minimal traffic may allow more debris to settle on a road, requires more frequent checking and cleaning. When I pass by a place where someone has just cut their grass and there are clippings in the road, I try to avoid it, and if I can't, I know I have to check the system when I get back home.
Condenser prior to cleaning attempts. Between condenser and radiator. View through front of condenser after cleaning attempts.
While there are several potential problems when diagnosing overheating in a C5, I want to toss in my experience. YMMV. My 2003 wasn't so much overheating, but the engine temp was just all over the place, which I was uncomfortable with. I checked the usual things, including changing out to new antifreeze. One quick point here is that Dexcool is not compatible with some other types of antifreeze. Some people hate Dexcool, and I understand, but if you are not using Dexcool, you should flush all the old Dexcool out prior to changing to a different type antifreeze to be safe. Read about it. So when I checked for debris buildup, the first picture is the front of the condenser prior to cleaning. The second photo shows the area between the radiator and condenser. The third photo shows the front of the condenser after cleaning attempts. To get to the point, cleaning the radiator to improve cooling is not necessarily as easy as just blowing compressed air (carefully) or just back-flushing with a water hose. Especially look at the pic of the area between the radiator and condenser. Don't trust that back-flushing water through the radiator to clean the condenser is going to be very effective. Air has to go through the condenser to get to the radiator, so I'm going to stretch and say if you haven't removed the cover and back-flushed both the radiator and condenser seperately, you may still have debris blocking the air flow. Maybe if one cleans very frequently, this could maintain air flow, but once you get imbedded debris, back-flushing may not be as effective as you think. In my case, once I determined that debris was going to be difficult if not impossible to remove, I cut my losses and replaced both the condenser and radiator. I did go with a DeWitts radiator, and I am happy with that. I have rock solid cooling, but my problem was ultimately imbedded debris I was unable to clean out. One more bit of advice is that routine cleaning should occur more often in areas you live that may have more debris on the road. In my case, a rural area where minimal traffic may allow more debris to settle on a road, requires more frequent checking and cleaning. When I pass by a place where someone has just cut their grass and there are clippings in the road, I try to avoid it, and if I can't, I know I have to check the system when I get back home.
Condenser prior to cleaning attempts. Between condenser and radiator. View through front of condenser after cleaning attempts.
Thanks for the great pics!!! Perfect example of a radiator/condenser in desperate need of a good cleaning.......
Y'all may want to consider getting a screen for your radiator. This is from my 89 but I put one on the 04. I see all the radiators that are junked up and this is an easy, cheap prevent.
From your original post your temps are fine above 35mph, that would prove your system is clean enough and functional. That leaves only your fans in question, suggest you recheck operation. Drivers side fan can only be seen from below, ramps or lift.
Start cold C5, a/c on, both your low side fans should run within a minute and cycle at 219psi on and 180psi off. If thats not sufficient cooling both high side fans should run at 255psi on and back to low at 219ps. If operating temp reaches 185deg both low side fans should run. If a/c is not working you'll have to wait for temp increase, both low side fans on at 226deg on and off at 219deg. Both high side fans should come on at 235deg and back to low at 226deg.
Good luck.
Overheating issue
