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Reads low coolant level when not. Bad sensor??

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Old Jun 9, 2013 | 07:53 PM
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Default Reads low coolant level when not. Bad sensor??

I've got a 98 and after changing out all the coolant and flushing the system along with transplanting the coolant level sensor to a new coolant reservoir it now keeps reading low coolant level when it's not low.
Bad sensor???
Looked fine when I pulled it out and checked it
Input would be appreciated
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Old Jun 9, 2013 | 08:21 PM
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I don't think so, the new tank came without one and the old tank with sensor out looks exactly the same, the sensor has a rubber o ring to seal it just like electrical connections do in the cars. And you push it into the tank opening for it and then plug on the electrical connection.
I was trying to figure just how it works though.???
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Old Jul 15, 2013 | 09:27 PM
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Originally Posted by nyelectrify
I've got a 98 and after changing out all the coolant and flushing the system along with transplanting the coolant level sensor to a new coolant reservoir it now keeps reading low coolant level when it's not low.
Bad sensor???
Looked fine when I pulled it out and checked it
Input would be appreciated
I have same issue with my '98. Did you figure it out?
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Old Jul 15, 2013 | 10:37 PM
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Originally Posted by nyelectrify
I don't think so, the new tank came without one and the old tank with sensor out looks exactly the same, the sensor has a rubber o ring to seal it just like electrical connections do in the cars. And you push it into the tank opening for it and then plug on the electrical connection.
I was trying to figure just how it works though.???
Originally Posted by Dads C5
I have same issue with my '98. Did you figure it out?
Wrong year tank.
The 00-04 tanks likely use the same molds as the early tanks, but the spot where the sensor gets installed is sealed off on the 00-04. You can not simply swap the sensor from a 97-99 to an 00-04 without modifying the tank.
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Old Jul 15, 2013 | 10:38 PM
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I have a 99 and the sensor was part of the tank, the newer ones don't, could be wrong on that. But, you probably got the wrong tank as mentioned.
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Old Jul 15, 2013 | 11:15 PM
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SOLVED --- I had this precise problem on my 99 recently. Solution is to buy a new overflow tank. It comes with the sensor installed/attached. The sensor is not sold separately from GM yet.

Of note, there are some large vendors here who have good prices... but I got mine direct from AC Delco via Amazon PLUS shipped it 3 day for less than the discount price elsewhere.

Alternative - connect the wires to themselves. Apparently, from searching the forums here, the indicator only lights up when the connection is broken. Connect them and you'll never have the signal pop up again.
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Old Jul 16, 2013 | 12:30 AM
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I get the low coolant warning from time to time on my 99. It always/only seems to happen when I am stopped in a somewhat nose down position, like the end of my driveway. Never had any temp problems so I have left it alone.
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Old Jul 16, 2013 | 08:53 AM
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Originally Posted by f6john
I get the low coolant warning from time to time on my 99. It always/only seems to happen when I am stopped in a somewhat nose down position, like the end of my driveway. Never had any temp problems so I have left it alone.
I was going to mention this, this is one known "malfunction". I have had it happen to my 1998.

I am thankful that the Corvette has a low coolant level light and a low oil level light, all cars should have these important warning lights!
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Old Jul 16, 2013 | 12:25 PM
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99 6mm Had the same problem with the low level. After much adjusting and fooling around, I finally found out that the level WAS actually LOW ! Added a small amount of fluid and have had no more problems. I know this sounds goofy, but it actually happened. Add some fluid and see what happens.
My 2 cts.
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Old Jul 17, 2013 | 09:21 AM
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I've had this problem with my '99 for a long time as well. It seemed to happen at the same stoplight everyday on my way in to work. It's definitely a "nose down" stop so I thought that or one of the sensors in the road messed with it. I always just cleared it because I knew I wasn't low on coolant. Recently the plastic T for the hose hookups on my surge tank cracked so I replace the surge tank with one from '97-'99 and it came with a new coolant sensor and sure enough it still goes off daily even though the coolant level is fine. I am seriously considering just wiring the terminals together to never get it again.
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Old Jul 17, 2013 | 10:20 AM
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For what it's worth, try adding a small amount of fluid, even though it reads full, and see if it solves the problem. It did in my case.

The Big Guy !
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Old Jul 22, 2013 | 06:09 AM
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I had replaced the coolant reservoir and found out that they gave me the wrong one. Problem solved. Turned out that from 97 for a few years they have sensor. After that they don't.
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Old Jul 22, 2013 | 04:01 PM
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Originally Posted by f6john
I get the low coolant warning from time to time on my 99. It always/only seems to happen when I am stopped in a somewhat nose down position, like the end of my driveway. Never had any temp problems so I have left it alone.
There was also a technical service bulletin many years ago for the earlier model years that involved shimming the tank with washers. If I can find that old bulletin I'll try to repost it here.

Here's another forum link that discusses the low level issues as well. It's an old posting but may help.
http://forums.corvetteforum.com/c5-t...t-message.html

And another link to owners with the similiar problem
http://forums.corvetteforum.com/c5-t...urge-tank.html

Also just another FYI. Sludge can build up on the float inside the tank on the earlier models. Just removing the tank and rinsing with clean water and shaking it a bit may free up the float. Just something to try before anything else and it costs nothing.

Last edited by MG RED 99; Jul 22, 2013 at 04:21 PM.
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