c5 overheating problem

One year ago at about 85K miles, my 2000 started to overheat. It came on suddenly. One day it was running fine, next day the temps skyrocketed into the red, even while driving on the freeway. I replaced the thermostat but likely did not purge (burp) the system properly and was still having the same exact issue. So, I replaced the water pump with a Bosch pump. I refilled and burped the system as instructed and bam, no more overheating issues. The car ran perfect as before. When the temp would hit 230, the fans would hit high and drop in back down to 220. While driving, it rarely would go over 200. I realize that if I had burped the system when I replaced the thermostat, it would have likely been fine and not needed the water pump. Lesson learned. The water pump was not leaking or making noise. When I took it off, it spun just fine and the impeller didn’t appear to be clogged. I replaced it anyway.

Now, again, at 101K miles, the car is all of a sudden overheating. Only this time, it will stay cool while driving, but then overheat in traffic. Once the temp hits 220, it skyrockets up past 240 and both fans turn on high but the temp will continue to slowly creep up to the red. I took the radiator cover off and there was a good amount of debris. I bought a long BBQ grill brush that would fit down in between the condenser and the radiator and brushed all that crap out of there and off the front of the condenser. I still had the same problem. Then I replaced the thermostat and burped the system. I still have the same problem.

If it’s debris still stuck in the radiator fins, wouldn’t I see temps gradually increasing over time instead of all of a sudden? Also, the water pump is only a year old. Now, this doesn’t mean it can’t fail, but I’m thinking that the radiator is possibly clogged inside and/or the fins are probably still full of junk that the brush didn’t get out. Both hoses are hot with the one near the thermostat being hotter as it should. The fact that it runs at normal temps while driving leads me to believe it’s not the pump.

I don’t want to spend money I don’t have to. From what I’ve described, what do you think it is? Radiator problem or the water pump again? Is there any way to clean out the radiator without pulling it? The fans appear to be turning on at the correct temps. I did the water pump myself and it was a bitch to get the gaskets lined up and a couple of the bolts back in, but an hour or so and many curse words, I got it all together. I used the opportunity to replace all of the idler pulleys as they were easily accessible with the water pump off.

Bad Overheating Problem in C4

I haven’t managed to find out what is causing the overheating. I was driving down the road when my water temp shot up to 290. I pulled over and popped the hood. The coolant reservoir was overflowing and boiling. I let the car set and cool and started back to my home. I was going 55mph and the car temp kept increasing. I pulled over again and waited 30mins. I managed to get back home safely with a temp of 170. The next day I went and tried to find out the problem was. The first thing I did was check the radiator. I figured it was blocked since as I drove, the temp still increased. The radiator was clean and unblocked. I then started up the car and let it idle. The cars temp increased fast. Both fans kicked in but they effected nothing. After a while, I heard a high-pitched whining noise. It was the water pump. I figured that was it, the water pump must be broken or breaking. I replaced the pump along with the thermometer. I let the car idle again and it stayed around 230. I then went for a drive, as I drove, the temp started to decrease. One thing I noticed though was the analog water temp gauge seemed to be broken, it went past 260 and stayed there, also when I started the car up, both fans started running and didn’t turn off. The car seemed to run fine as I drove. Near the end of my drive though, the temp hit 150 and stopped. I pulled into my drive and popped the hood. It was boiling again, steam coming from both the reservoir and engine this time. The thermostat stayed at 150 though. It never increased or decreased. I believe the problem may be the radiator but I might be wrong

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c5 Corvette harmonic balancer issues

Bad harmonic balancer symptoms include engine vibrations, unusual noises, an illuminated check engine light, and a noticeable wobble while the engine is running. You should always replace a faulty harmonic balancer right away because it can cause serious damage to the serpentine belt and engine-driven accessories.


A To Z Auto Care will take the guesswork out any Corvette Repair