[kasper37]

I recentrly replaces a radiator on my 1995 chevy motecarlo 3.1 engine the issue that I am having is that the low coolant light on the dash board comes on and off periodically I check the level of the coolant and it is normal why is it the low coolant light in the dash board keeps coming on and off.

[this8384]

The coolant level sensor in the overflow tank is bad. Go to GM; the part itself shouldn't be more than $20-30.

[kasper37]

[QUOTE=this8384]The coolant level sensor in the overflow tank is bad. Go to GM; the part itself shouldn't be more than $20-30.[/QUOT

Is this common to happen, do the sensors normally go bad when you change a radiator?

[this8384]

Not when you change the radiator, but the sensors themselves go bad quite frequently. Odds are that GM will have at least 1 already in stock because it's such a common failure part.

[CaptainRich]

DESCRIPTION
This lamp will be illuminated when engine coolant level in the radiator drops below a predetermined level. To turn lamp off, check cooling system, then add coolant to bring system to proper level.
After doing service on the cooling system, it is crucial that all the air is bled from the cooling system.

Diagnosis W/ Low Coolant Indicator On W/coolant level OK:

[this8384]

Not accurate. The sensor is mounted into the radiator.

So I was right about the diagnosis, just not the location... want to go half-sies? *lol*

[kitch428]

Specifics. We must have specifics. One wrong word will throw everybody off and disagrees start flyin'. Lol

[kasper37]

DESCRIPTION
This lamp will be illuminated when engine coolant level in the radiator drops below a predetermined level. To turn lamp off, check cooling system, then add coolant to bring system to proper level.
After doing service on the cooling system, it is crucial that all the air is bled from the cooling system.

Diagnosis W/ Low Coolant Indicator On W/coolant level OK:

The bleeder on this vehicle is broken, is there any other way to bleed the radiator?

[CaptainRich]

the bleeder on this vehicle is broken, is there any other way to bleed the radiator?

Without that bleeder functioning, purging the system will be difficult.
You may find this funnel useful in reducing the amount of trapped air:



Lisle LIS22150 Coolant Funnel w/ Radiator Fill Adapters LIS22150 Automotive Cooling System Service Tools

[kasper37]

Without that bleeder functioning, purging the system will be difficult.
You may find this funnel useful in reducing the amount of trapped air:



Lisle LIS22150 Coolant Funnel w/ Radiator Fill Adapters LIS22150 Automotive Cooling System Service Tools

Ok, well the reason that the low coolant light was illuninated was because the replaced radiator was defective, I replaced it with another one I also replaced the bleeder pipe so now I could bleed the line, however now it seems to me that the cooling fan is not coming on, I made sure that the wires were connected but I have not seen the fan come on, the temperature gage is not showing that is over heating but I feel that the engine is very hot, and like I said I have not seen the fan come on at all. What did I do wrong?

[CaptainRich]

I don't think you did anything wrong... yet. You're just not done... yet.

The cooling fans operate from a coolant temp sensor, but not the same one that controls the gauge on the dash.
Without the A/C on, the fans aren't supposed to come on until the coolant temp at that sensor reaches 230° F.

If the temp gauge isn't indicating an overheat (into the red) then you may not have reached the temp that enable those fans on. And you probably won't sitting at idle, unless it's mid-summer in the south and you don't have the A/C on.

If you seriously want to see if the fans will come on from temperature only, you need to hold the idle high enough and long enough for the coolant temp to reach that spec. It's going to seem extremely hot before they do.

I think if you are confident that you've thoroughly purged the air and the cooling system is full, just drive the car as you normally would and keep an eye on the temp gauge for the first few days or so to see if the temp does wander too high. I'm hoping you're just nervous about the repairs and simply being overly cautious. Let me know...

[Grayson301]

Welp Kasper first tings first ,the low coolant sensor is a known item to go bad as that I repair vechicals for a living.. 23 years worth of it.. I can tell you know that sensor has cost folks a many a towing bill because it uses a 5 volt v-ref that's generated out of the pcm , when the sensor DIES it shorts out the 5 volt out of the pcm and causes a no start.. for this reason I tell you just unpulg it and then make a weekly routine of checking the fluids once a week.
Now
This system will bleed itself even if the bleeder will not open. Just run it in 7 minute cycles with a 2 min. pause between the run cycles
The Cooling fan WILL NOT come on till the vehical reaches 223 plus degrees. Therefore a antifreeze mix is needed since water BOILS at 212 degrees.
When the cooling fan does come on around 223 it will stay on till it reaches 212-217 degrees
So yes the vehical does run on the hot side. Just remember that when you think of opening a radiator cap on a hot engine... silvadine rubs on fresh burns is no fun