While driving to work on a cool day my temperature gage pegs in less than a minute. I pulled over turned on the air waited a minute or two and as quick as it pegged it returned to normal. After doing a search on this problem it recommended to make sure the battery was in good condition. I had the battery and charging system checked at the local auto parts store and the battery was at 69%. Had it charged and put it back in and it read 69% again after reading fully charged on the charger. The store replace the battery and showed me that the alternator passed (in car test).

I drove to get dinner later that night and again within about 7 miles it pegged again then within a minute or two it started to return to normal. When I got home I opened the hood and put my hand on the reservoir bottle and it was warm but not hot I could leave my hand on it.

This car is driving me crazy with all the phantom electrical issues it's had. Before summer it overheated on the way to work that time it was hot. I had it towed to the dealer and after two days they could not find anything wrong. Both fans came on at the right temp and all seamed ok. The check engine light came on but during the tow it was off when It got to the dealer. I had the antifreeze changed and it work normally through summer when the daily temperature ranges 105-115

I'm ready to put it in the shop on Monday but I'm afraid they'll keep it for a couple of days and again find nothing wrong. Help Please...this car has had most of the C5 electrical problems listed on the site. I'm also having problems with my fuel gage as well. I fill the tank go into a store start the car and it reads half a tank then will very slowly work it's way to full and then be ok for a while. I bought some Techron and will try that before my next fill up. I don't expect that to work as I always use supreme Chevron gas with Techron. I'm slowly pulling out what hair I have left.

 

An old thermostat which begins to stick will exhibit this temperature gauge symptom.

The fuel gauge symptom is likely caused by deposits on the tank sender unit. Techron will likely fix the problem, but it may take several applications.

You didn't list the other electrical problems, but they may completely unrelated to the fuel gauge and temperature symptoms.

I would start by changing the thermostat, particularly if it has not been changed in a number of years.

What are the other electrical symptoms?

 

The other issues appear to be corrected. But for info I had to repair the DCM harness on the drivers door inside the door jam as the pin that supplies power was not making good contact my DIC would display every problem it could list and nothing on the drivers door module worked. This problem was intermittent. So far so good.

I had a problem with the turn signals and had to replace the flasher unit a fun little job.

I also had a problem with the left headlight and had to rebuild the motor the gear was stripped. Shortly after that I had to replace the drivers door window regulator.

The right headlight motor was replaced by the dealer when it quit.

The passenger door window motor had to be replace because it quit working

I don't think any of these are connected to the temp issue and I couldn't find a connection between the fuel gage issues and the temp gage on this site but anymore who knows. They both started within the last two weeks.

I'm thinking about looking for an exorcist!!!

 

I under stand what you say about the cap and sudden temp rise and fall. Do they go bad like that this one has only been removed once since I've owned the car and that was this year when they changed the antifreeze? What color is the factory coolant wouldn't I notice it leaking in my driveway if I had cracks in my reservoir???

I agree with your opinion about the problem because I've never seem temperatures drop that quickly after reaching 260+

 

Would you recommend a pressure test of the cap and cooling system to better isolate the problem??

I just looked at the surge tank and hoses and they appear fine the same amount of fine dust on all no cracks visible no signs of seepage

 

Yeah I thought about what I asked you and yeah the cap has been doing it's thing for the last 13 years. My local auto parts store has a 15 lbs. cap for 5 bucks in stock and the 18 lbs. for 16 bucks but you have to special order the 18 pound cap. Is there an advantage to going with the 18 lbs. cap?

Also what is the easiest way to bleed the air from the system? do you feel that will be necessary if it's the cap my tank has antifreeze in it about 1/3rd from the bottom.

 

I just checked the water pump and it appears to be dry however I noticed a reddish brown seepage on the frame below the transmission lines at the block area and I have noticed reddish brown spots on the garage floor at night which I thought were condensation from the air conditioner. Now I feel there my be a slight drip from the transmission lines. they feed into a different part of the radiator correct?

also I could not find a dipstick for the transmission to check the fluid level there is one right?

 

Thanks for the bleed procedure my driveway is sloped. The 18lbs cap list as OME cap and the 15lbs meet OEM specs. $5.00 bucks would be a cheap fix. I checked the upper hose and no collapse however I had started the car about 3 hours ago long enough to more it back about 3 feet to make sure I hadn't sucked up a trash bag even though I felt pretty strong that wasn't the issue.

 

Thanks for clarification on the dip stick. I just tried the bleed procedures what a mess and I'm concerned. Pushed the car out of the garage and onto the slope of my driveway so the rear of the car was at it's lowest point. Removed the cap and ran for a minute at idle, put on the new cap and ran until 210 was reached, removed the cap and ran for a minute with antifreeze spewing out of the surge thank the temp got to 230 the next step replace cap and run until 210 again power down remove cap and top off. it never got to 210 just kept going up and the surge bottle is full to the top I'm going to have to let it cool down before I can get the cap off again.

Any thoughts

 

Thanks for the link I reviewed it and the attempts the other guy had to go through before finally getting it to work. If it's an air problem I think it's worse now than it was. Now it starts to overheat after about 5 blocks for the house when I drove it home Friday it's 17 miles from work to home and it didn't overheat coming home only in the morning going to work when it was cooler outside. Go figure. I had to stop 3 times tonight because it was reading 250+ I would turn it off and in about 15 minutes it would drop 30 degrees. I've never had a car cool off that fast once it red lined. When I turned into the garage the gage was reading 255 I turned it off opened the hood and placed my hand on the top of the surge bottle it was warm but not hot you would think I would have burned my hand and the antifreeze was not boiling like it did when it idled for 1 minute with the cap off after reaching operating temperature.

I'm not sure the temperature gage is reading correctly. I know the passenger fan was working earlier today because I checked it not 100% sure about the drivers side as it's harder to see.

At this point I think I've had enough, have it towed to GM tomorrow I don't think I want to mess with it for days on end only to get it to stop but not knowing for sure if it's fixed for good or if I got lucky for a couple of months. I've never worked on a car like this where every 3 or 4 months it's something else. I've had over 30 different vehicles and never have I had to burp a cooing system.

Thank you Again

 

Just got the call from the dealer they said the thermostat was stuck shut. However they stated that there has been a redesign of the thermostat and their mechanic recommended changing the water pump to accommodate the new thermostat design.

You don't want to know how much they quoted. I just looked on line at the price of the water pump and thermostat and unless I'm missing something I could buy several for what they quoted. I've replaced them on other cars but them I'd still have to remove the air from the system. Not sure I'd have luck with that. The water pump is 13 years old with a little over 50,000 miles could last longer or not. So I told them to go ahead.

Just thought you should know
Thanks for your time.

 

Sounds like a good time to replace the water pump. Glad the solution is at hand.

 

Vegas99,

I can see you are a recent forum member and have not listed your location. If you have read other posts you should have seen the term dealer changed to stealer, this is not a typo as you are finding out. Your car is 13 years old, I would recommend you find a good local shop that knows vetts. List your location and someone here might have a good referral for you. Also reach out to your local Corvette club for recommendations.

Changing the water pump and thermostat on this car is not that difficult. I pulled both of mine out and replaced with an electric pump a few years ago. It is easier if you have two people to guide the water pump in with the rubber "O" rings but not an overly complicated job.

One thing I have learned from this forum is to not be afraid of this car. If it is something that can be unbolted or unplugged you can probably do it yourself.

If by your handle implying that you are in Vegas you may want to consider a fan upgrade and have your fans tuned to come on earlier and use a 165 degree Tstat. I've done both to my car and am satisfied with the cooling I get now.

Best of luck.

 

You're right about my location. And yes I am a pretty fair mechanic and replaced many a water pump or thermostat in my day and I should have done this one for the price, nothing like paying triple for the price of parts at the dealer.

Using forum advice I have repaired many things on this car already. But I spent most of the weekend trying to correct this issue without success. In fact it got worse. I'm still not happy with the cost but I am happy that I wont be doing the work. There are just sometime the money isn't important. Not say I'm in the habit of throwing my money away if I was I probably never would have owned a Corvette. I'm usually up for a challenge but this time decide to throw in the towel. Besides I already had it towed to the dealer and that wasn't cheap either. If you can refer a good local Corvette guy I'm all ears

Thanks