billscamaros

iTrader: (1)

'99 Z28 M6 - there is a sensor mounted on the backside of the radiator, passenger side, beside the battery. It's a square gray box that attaches to the radiator, with an o-ringed round sleeve that inserts into the radiator.

What is the purpose of this sensor? When I got to work today, after my 58 mile commute, I backed into a parking space. I was sitting with the car idling, and all of the sudden steam came out from under the hood. I shut the car down, popped the hood and found antifreeze streaming from where this sensor belongs. The sensor itself was laying on top of the bottom radiator hose. It's got a metal clip that holds it in place. I popped it back into place, and it held all the way home tonight.

Other than the steam, there wasn't anything to indicate that there was a problem. My temp gauge was steady in the normal location.

So I'm curious as to what this sensor does.

Thanks

Bill

Tuffguy610

iTrader: (2)

Hey Bill,
That sensor you are talking about is the coolant level sensor. When it popped off did a light come on in your upper left corner of the dash that looks like a tank with an arrow on it? If so, that is your low coolant warning light and it should have went off given your circumstance. Your temp gauge read normal because 1999+ F-bodies have a dummy temp gauge on the dash that almost always shows normal temperature conditions unless your engine has basically already overheated. This would explain why your temp gauge showed a normal temperature even though your sensor blew out of your radiator. The 1998 cars were the only LS1 cars to have an accurate temp gauge and they changed it in 1999 because it was rumored that there were too many complaints and warranty claims due to the fluctuations on the temp gauge on the 1998 and earlier cars.

14k

can you put the 98 gauge in a 01? id rather have actual reading instead of a dummy

billscamaros

iTrader: (1)

Thanks Tuffguy ..... no, the light did not come on. I plan to replace the sensor as in the area around the probe looked a little chewed up.

Any idea on the answer to 14k's question ..... is it the actual guage that is different, or the sending unit?

Thanks

Bill

2001NBMZ28

The '98 system is different, simple answer is no.

Tuffguy610

iTrader: (2)

Yup, the 98 LS1 F-bodies were the oddballs out of all the 98-02 cars. They had a bunch of different features to them versus the 99-02 cars. Mainly the valve covers were different, and apparently the tune was different as well. They also started putting "black boxes" in the 99 cars that recorded a few seconds of data prior to a crash. I am pretty sure there are other differences as well and this website will be able to identify them if anybody is curious. There are good write ups and stickys around here somewhere.

Tuffguy610

iTrader: (2)

Also, I'm not sure why your low coolant light did not come on, it should have since the sensor didn't detect any coolant as it was lying on your radiator hose. I did an LT1 radiator swap when my stock radiator blew up, (LT1 radiators are thicker than LS1 radiators because the LT1s had an iron block) and now for some reason my low coolant light comes on even though there is no coolant leaking and the system is fine.

wssix99

iTrader: (5)

This is not normal... Check the flange on the sensor bung. This is what the metal clip engages. Either the sensor was replaced without the clip being on right or that flange broke. (Yep - it's plastic.)

billscamaros

iTrader: (1)

So I picked up a new sensor and replaced the old one.

Tuffguy - the old sensor was disconnected ..... the pigtail was taped off below. The indicator light has never been on .... I've had this car for years now and have never had to investigate this light or sensor. I plugged the connector to the sensor, and the indicator light comes on, even though I have verified that the coolant level is above the sensor. Any ideas?

Tuffguy610

iTrader: (2)

Hmm, not sure, maybe the sensor is bad. I have the same problem but I think my radiator dumps alot of coolant into my reserve tank on long trips and then draws it back in when it cools down.

wssix99

iTrader: (5)

Could be a dud sensor if the light goes off with it unplugged.

2001NBMZ28

They went bad all the time, that's why GM finally took them off our cars. Instead of replacing the sensor, most people just disconnected it to keep the warning light off. Assuming the new sensor/wiring is good make sure you got all the air out of the system when you installed it.

billscamaros

iTrader: (1)

So how can I check the sensor? Just check for resistance across the two terminals within the connector? I've put close to 200K miles on this car with this sensor disconnected ...... I would never have thought about it until the old sensor popped out of the radiator. So I'm comfortable leaving it disconnected.

wssix99

iTrader: (5)

If the light is off with it disconnected, then the sensor is bad or you have some wicked corrosion in the connector. A good submerged sensor should give an open circuit just like having the connector unplugged.

BTW - All parts on cars go bad over time and these are no exception. GM changed several cooling components in 2000, so saying that they were removed because they "suck" wouldn't really be accurate. Given the way engineering works in the real world, something else must have changed to the point where the sensors didn't have as much utility. All I know is that my sensor saved my bacon when my 1999 water pump started dying on me. (So, I'll be a big fan of these or a while. $35 every couple of years is far better than having to replace an engine.)