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Old 12-13-2012, 09:45 PM   #1
Mustang_Eater
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Default Low Coolant sensor?

Hi All,

I keep getting low coolant on my dash on and off randomly. Every time I check the the coolant if full? Although I do notice some very small drips of coolant when I park on a angle.

Is it just the 1 sensor stuck into the front of the radiator? I'm thinking of replacing the sensor.... anyone have any ideas?

1989 Coupe

Thank you,
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Old 12-13-2012, 10:17 PM   #2
jesredvette
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I have the same issue with my '88 vert; full coolant and still get the intermittent 'low coolant' light. I'd be interested as well to get input on this.
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Old 12-14-2012, 12:04 AM   #3
leesvet
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huh uh-huh
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Don't go buy another sensor...these are stupid simple.

They can get crud caked around the tip so its not making contact with the water.
This is a simple electrical circuit..water is up high enough to cover the tip of the sensor, circuit closed. Water drops down low and the tip is exposed, circuit open and that gets you a lite.

You can pull that thing out and clean. Its just a rubber plug with a thin metal tab pushed thru the center. Not special at all. Re-insert with maybe a smear of RTV silicone sealant around the rubber and pop it in.

There is the possibility that your system is actually low....at rest the water can be up to the filler neck. Looks full when engine is off and cap is off. Leave cap off and start up...the level suddenly drops 4" when the pump starts pulling it out of the radiator and pushing it thru the block. Theres your void the sensor "feels". Sometimes its just time for a little water in the overflow, or it may be an indication of a leak. The water went somewhere...thats the question. Fill bottle, fill radiator, run engine at fast idle, top off and place cap on while engine is running 1000-1200 rpm. If you top it off at that rpm the pump is full and so is everything else. Next, drive and see if this happens again. Hopefully not, but if it does go low again, look at the cap, see if its getting out thru the over flow tank or if there is an external lean in a hose or gasket.

Sometimes you can just pull the wire off the sensor and push it back on and thats all it is....
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Old 12-14-2012, 06:26 AM   #4
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Quote:
Originally Posted by leesvet View Post
Don't go buy another sensor...these are stupid simple.

They can get crud caked around the tip so its not making contact with the water.
This is a simple electrical circuit..water is up high enough to cover the tip of the sensor, circuit closed. Water drops down low and the tip is exposed, circuit open and that gets you a lite.

You can pull that thing out and clean. Its just a rubber plug with a thin metal tab pushed thru the center. Not special at all. Re-insert with maybe a smear of RTV silicone sealant around the rubber and pop it in.

There is the possibility that your system is actually low....at rest the water can be up to the filler neck. Looks full when engine is off and cap is off. Leave cap off and start up...the level suddenly drops 4" when the pump starts pulling it out of the radiator and pushing it thru the block. Theres your void the sensor "feels". Sometimes its just time for a little water in the overflow, or it may be an indication of a leak. The water went somewhere...thats the question. Fill bottle, fill radiator, run engine at fast idle, top off and place cap on while engine is running 1000-1200 rpm. If you top it off at that rpm the pump is full and so is everything else. Next, drive and see if this happens again. Hopefully not, but if it does go low again, look at the cap, see if its getting out thru the over flow tank or if there is an external lean in a hose or gasket.

Sometimes you can just pull the wire off the sensor and push it back on and thats all it is....
Yep what he said. Also the FSM says it may take up to 3 cycles to pull enough back from the recovery tank before light stays off. ( cycle is full operating temp to complete cool down ) It works, ask me how I know.
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Old 12-14-2012, 07:38 AM   #5
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Quote:
Originally Posted by leesvet View Post
Don't go buy another sensor...these are stupid simple.

They can get crud caked around the tip so its not making contact with the water.
This is a simple electrical circuit..water is up high enough to cover the tip of the sensor, circuit closed. Water drops down low and the tip is exposed, circuit open and that gets you a lite.

You can pull that thing out and clean. Its just a rubber plug with a thin metal tab pushed thru the center. Not special at all. Re-insert with maybe a smear of RTV silicone sealant around the rubber and pop it in.

There is the possibility that your system is actually low....at rest the water can be up to the filler neck. Looks full when engine is off and cap is off. Leave cap off and start up...the level suddenly drops 4" when the pump starts pulling it out of the radiator and pushing it thru the block. Theres your void the sensor "feels". Sometimes its just time for a little water in the overflow, or it may be an indication of a leak. The water went somewhere...thats the question. Fill bottle, fill radiator, run engine at fast idle, top off and place cap on while engine is running 1000-1200 rpm. If you top it off at that rpm the pump is full and so is everything else. Next, drive and see if this happens again. Hopefully not, but if it does go low again, look at the cap, see if its getting out thru the over flow tank or if there is an external lean in a hose or gasket.

Sometimes you can just pull the wire off the sensor and push it back on and thats all it is....
Let me get this straight, it just "pulls" out? I thought it was bolted into the radiator and I would have to un-bolt it to take it out? Your post reads like it is just pushed into the radiator? Help, please?
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Old 12-14-2012, 07:46 AM   #6
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It's not bolted ,its only plastic, it just snaps into the hole in the radiator..There are 2 prongs that snap over a small ring on the outside of the hole, this holds it in.It's pretty fragile and you can break the prongs fairly easy , so be carefull....WW

Last edited by WW7; 12-14-2012 at 07:49 AM.
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Old 12-14-2012, 08:58 PM   #7
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I had a similar problem a few years ago with my '94.

On mine it turned out to be a faulty reservoir pressure cap. Because of that the radiator wouldn't pull in more coolant and the light would come on. Changed the cap and no more light. It drove me crazier trying to figure it out.

Good luck.
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Old 12-15-2012, 01:45 AM   #8
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Quote:
Originally Posted by QCVette View Post
On mine it turned out to be a faulty reservoir pressure cap. Because of that the radiator wouldn't pull in more coolant and the light would come on. Changed the cap and no more light.
My '86 doesn't have a reservoir like the later models, but I fixed my low coolant light problem by replacing the radiator cap.

There are two kinds of sensors. The first one has hooks that snap into a groove. The second screws in:

Click the image to open in full size.

Click the image to open in full size.
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Old 12-15-2012, 11:09 AM   #9
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Use the proper radiator burping procedure (see attached) AND, drill the small holes in your thermostat as directed and your Low Coolant light problems will be solved.
Attached Images
File Type: pdf Corvette L98 Radiator Burp Procedure.pdf (72.8 KB, 44 views)
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Old 12-15-2012, 11:54 AM   #10
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Awesome, thanks all. I try all you ideas and let you know what happens.
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Old 12-15-2012, 01:06 PM   #11
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The plastic prongs will break after the sensor has gone through a years worth of heat cycles. After replacing mine twice, and numerours false positive alerts, I fabricated a grounding wire for the connector.

When the circuit is complete to ground the lite stays off. Maybe not the best solution but when I know the water level is correct and the alarm lite continues to stay on, I have a temporary resolve.

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