C5 Overheating HELP!!
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C5 Overheating HELP!!
So earlier today the battery in my 2004 Z51 (47k miles) decided to die. I had an optima red top battery in my garage & swapped them out instead of going & getting a brand new battery. So after I swapped them out I took the car out for a drive to get the battery charged up good. After a few miles I noticed that my temperature gauge was pegged at 260 degrees!!!! The car has never overheated so this is quite a coincidence. Does it have something to do with this battery swap??? Does something in the computer need to be reset?? I checked the coolant resevoir & it appeared full. Please help me out guys this car is my baby & I had to leave it on the side of the road tonight.
-Thanks,
Matt
-Thanks,
Matt
Last edited by 72Shark_VAL; Aug 3, 2017 at 11:22 PM.
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Was the AC on or off? Did your cooling fans engage? Did you check to see if a plastic bag or something got sucked up in front of your radiator?
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did it overheat or did the gage just read 260?
I have seen a C5 overheat....you would know. You say the coolant level looked fine.
did you perhaps run over a plastic bag that is blocking airflow to the radiator?
we need waaaay more info
no one wants to see your car sitting so help us help you
I have seen a C5 overheat....you would know. You say the coolant level looked fine.
did you perhaps run over a plastic bag that is blocking airflow to the radiator?
we need waaaay more info
no one wants to see your car sitting so help us help you
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I'm not sure if the cooling fans engaged or not. I thought about that a minute ago, is it possible that when I cranked the car with the optima in it it shocked the system & popped the fuse that controlls the fan switch? The crap battery I took out only had like 700 cranking amps. The optima I put in has 1000, maybe 1100 but I know it was considerably more. Does this sound like a possibility??
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I looked around everything I didn't see any blockages. & the gauge read 260 so I assumed it was correct...the motor was very hot to the touch. Do you think the gauge is wrong? The car didn't run or feel/sound any different when I noticed the gauge had pegged. I didn't hear any funny noises or anything alarming I just saw the reading & panicked
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I'm not sure if the cooling fans engaged or not. I thought about that a minute ago, is it possible that when I cranked the car with the optima in it it shocked the system & popped the fuse that controlls the fan switch? The crap battery I took out only had like 700 cranking amps. The optima I put in has 1000, maybe 1100 but I know it was considerably more. Does this sound like a possibility??
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I would go back, start the car, see if the fans come on....if they don't turn on the AC then they should come on for sure, if they don't then you have a fan issue and can pursue that
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At 260°, your car should have been boiling over. Was there any coolant overflowing the tank? You would have at least seen and heard the coolant boiling furiously in the tank. If not, my guess is you have something else going on with the sensor or your thermostat is stuck shut. How many miles did you drive before it "overheated".
Check for simple stuff like an obstruction in the radiator. If nothing, I would start the car and let it idle to operating temperature. Check to see if the fans kick on and check to see that the hoses and radiator heat up. If they do and the temp Gage pegs, try turning the heater to the highest setting and highest fan speed. Does that lower the temp per the Gage? If yes, you likely have an issue with the cooling system. If no, you likely have an issue with the gage sensor.
Check for simple stuff like an obstruction in the radiator. If nothing, I would start the car and let it idle to operating temperature. Check to see if the fans kick on and check to see that the hoses and radiator heat up. If they do and the temp Gage pegs, try turning the heater to the highest setting and highest fan speed. Does that lower the temp per the Gage? If yes, you likely have an issue with the cooling system. If no, you likely have an issue with the gage sensor.
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Good advice. Hopefully it is just a sensor issue.
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Alright guys so I went back & got the car this morning, took the old battery with me & swapped them out again/jumped it off & drove it home. It never even got over 205 degrees, all the gauges were working great. Oil pressure was great. So I guess the optima battery did make a difference. Very weird indeed
Last edited by 72Shark_VAL; Aug 4, 2017 at 08:29 AM.
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My 2002 did the same thing and it was a sticking thermostat. Pretty straightforward to replace and inexpensive too. Just be sure to replace the antifreeze with the correct type of Dexcool and burp the system to purge any air. Mine has been running perfect since . It did freak me out initially though. 
Thread Starter
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Joined: Oct 2016
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At 260°, your car should have been boiling over. Was there any coolant overflowing the tank? You would have at least seen and heard the coolant boiling furiously in the tank. If not, my guess is you have something else going on with the sensor or your thermostat is stuck shut. How many miles did you drive before it "overheated".
Check for simple stuff like an obstruction in the radiator. If nothing, I would start the car and let it idle to operating temperature. Check to see if the fans kick on and check to see that the hoses and radiator heat up. If they do and the temp Gage pegs, try turning the heater to the highest setting and highest fan speed. Does that lower the temp per the Gage? If yes, you likely have an issue with the cooling system. If no, you likely have an issue with the gage sensor.
Check for simple stuff like an obstruction in the radiator. If nothing, I would start the car and let it idle to operating temperature. Check to see if the fans kick on and check to see that the hoses and radiator heat up. If they do and the temp Gage pegs, try turning the heater to the highest setting and highest fan speed. Does that lower the temp per the Gage? If yes, you likely have an issue with the cooling system. If no, you likely have an issue with the gage sensor.
No there was no coolant overflowing the tank, no spewing noises, no bubbling or popping noises. It seemed to be operating fine but the gauge was just pegged. There was no obstructions in the radiator, & the fans were working. I don't know why the change to the optima battery made the gauge read that way, or if the gauge is slowly going back & it was all just a coincidence. But it sure appeared to be operating normal this morning when I drove it home. Oh & it had only been driven about 8-10 miles when I got the reading last night.
Last edited by 72Shark_VAL; Aug 4, 2017 at 09:49 AM.
Thread Starter
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My 2002 did the same thing and it was a sticking thermostat. Pretty straightforward to replace and inexpensive too. Just be sure to replace the antifreeze with the correct type of Dexcool and burp the system to purge any air. Mine has been running perfect since . It did freak me out initially though.
Last edited by 72Shark_VAL; Aug 4, 2017 at 08:43 AM.
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Ordered a new battery & 186 thermostat. I'll probably go ahead & pull the radiator out/ flush it & replace hoses if necessary while I'm at it. Do you guys think it would be worth it to go ahead & replace the pulleys too while the radiator is out? Seems like a good time to do it. It's only got 47k miles, but is 13 years old. Let me know what you think.
Last edited by 72Shark_VAL; Aug 4, 2017 at 01:45 PM.
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A good battery will not cause your problem. ALLOT of members on here use Optima batteries, both red and yellow tops.
On the other hand, low voltage can cause all sorts of electrical gremlins in the C5.
My 98 would purge the coolant tank at 245-250 degrees, even with a new cap. So, I would think if your car truly hit 260 degrees, it would have purged too. Therefore, I don't think your car overheated.
IMO, you don't need to replace anything on your cooling system but since everything is 13 years old, it sure won't hurt to do so. I believe Dex-cool's lifespan is 5 years or 150K miles, which ever comes first.
Yes, if I was in your shoes, I'd probably replace the belt, idler, and tensioner while everything is apart.
Melting Slicks
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A good battery will not cause your problem. A LOT of members on here use Optima batteries, both red and yellow tops.
On the other hand, low voltage can cause all sorts of electrical gremlins in the C5.
My 98 would purge the coolant tank at 245-250 degrees, even with a new cap. So, I would think if your car truly hit 260 degrees, it would have purged too. Therefore, I don't think your car overheated...
On the other hand, low voltage can cause all sorts of electrical gremlins in the C5.
My 98 would purge the coolant tank at 245-250 degrees, even with a new cap. So, I would think if your car truly hit 260 degrees, it would have purged too. Therefore, I don't think your car overheated...
I don't see how a good battery could cause that.Keep the temperature sensor in your short list.
Last edited by GCG; Aug 5, 2017 at 01:20 PM.