My "Add coolant" light started acting up recently. I found some info on here but nothing that seems to fit...

The light comes on after the car has been sitting. After a bit of driving it goes away, I want to say maybe around 50degrees, but I'm not 100% sure that's always the case.
But it does always stop alarming after a bit. Sometimes if it stops alarming and I come to a stop shortly after, and stayed stopped (like at a red light) it might start again. But after I start driving again it goes away for good.

It came on randomly, nothing happened to make it start doing that. I was actually really confused about this loud alarm that just started up. The first time it started doing this i was driving and turning into a gas station.

First thing I did was check the coolant levels, they were fine. I added a bit more to be safe.

I then checked to see if it was overheating, it isn't PC says 84-85. It isn't heating up any faster than usual either.

I then tried burping it to make sure there were no bubbles. Opened the AST and Filler cap ran the car for a while. Still no fix.

Should I just assume that the sensor is dying or something? I haven't looked at this yet as I don't know where it is or what it looks like.

My other worry was maybe a small blockage. At first I thought maybe ice, but that doesn't make sense considering how the sensor works...

Any ideas?

 

The sensor is on the front of the filler neck looking down from the bumper. It is a black plastic sensor with a single black wire coming off of it. The connector is a single tab white connector. They are known for getting brittle where the wire connects to the sensor

The sensor creates a ground when coolant is present. The wiring route connects the sensor to the emissions harness but it then goes through it and connects to the engine harness via what is called the coolant disconnect, beside of the PS pump. The wire from the engine harness is brown with a white stripe. Confirm this single wire plug is not loose. You can also connect a multimeter to each plug and confirm there is continuity. Giggle the harness to ensure there isnt a semi-break in the wire.

 

Also, since it comes on after its sitting, check the filler neck level of coolant before starting your car. If it's always a little low, you have a coolant leak or your engine is burning it.

 

It is usually the sensor in this situation. Spend the $30.00 to replace it and if that doesnt fix it run a new wire from the sensor over to the battery harness. 99% of the time it is the sensor.

 

I just did a quick look and the black cable at the sensor has exposed copper...
I guess Ill just get another sensor.

Thanks guys!

 

This is the part I want right?

Sadly it isn't 30bucks hahah, but I want that buzzing gone!
I'll call Ray Crowe

 

I want to say mine was around $70 from Ray

 

Or there's a clog in the line between the AST and the overflow preventing it from sucking coolant back from the overflow after shutdown.

Or you have a bad radiator cap that is not allowing the system to suck coolant back from the overflow.

 

If the line was clogged, it would never fill the overflow to begin with.

I agree with the radiator cap, but eventually the overflow would start puking coolant as he continued to add it. OP mentioned he checked coolant levels and they were fine.

 

Wouldn't the car overheat too with those two issues?

 

Thus my concurring with the sensor.

 

My car was giving me a light/alarm at startup and it was a restriction in the line. In my case it seems that there was enough pressure being generated to force coolant past the restriction to the overflow, but not enough suction being generated to overcome the restriction and pull it back the other way.

 

What did you do about it?

 

Yeah, that does make sense. Easier to push than pull.

 

I had an intermittent buzzer and had a slow leak at the sensor so I replaced it and still had the intermittent buzzer even with full up coolant. I put a stick pin through the wire and grounded it and it still buzzes when it feels like it, so the issue with that car is somewhere else, not the sensor. The exposed copper on the wire on your sensor is not a big deal, I would not replace it for that.

Replacing the sensor can be a lot of work since the plastic tends to deteriorate over 20 years and it can crack apart upon removal which means you have to remove the housing and get all the plastic pieces out before installing a new one.

Another issue is that the threads on the housing can get a little tight which means you probably want to run a tap in the hole to clean them up before attempting the install of a new sensor. An alternative to buying a tap is to find a bolt of the same size, cut a little groove or grooves in it with a dremel cut off wheel and use it like a tap to clean up the threads. Again, the sensor is plastic and therfore can't take too much torque on installation before cracking (guess how I know this, but I was able to salvage and use it).

It makes more sense to test the circuit before spending $80 with shipping for a new sensor and lot of time replacing it if the problem might be somewhere else.

 

Did you ever find a solution as to why it goes off on your car?
I mean it only stays on for 2-3 minutes then it goes away so I guess if I just have to live with it, I will. It sucks but if thats the only problem...

 

Not yet, but I think that the buzzer is also tied to the oil level sensor and I ohmed that out when I changed the oil last week and it read the same whether the sump is full of oil or empty, so I want to check that out as well as the wiring on top of the engine.

 

That's interesting...
Keep me posted as you do this.
I'm a bit worried if there is a clog how it might affect the car. I kind of doubt that's what it is. I really think its electrical.

 

Pulled the hose off at the AST, blew air through it which sent the clog back to the reservoir.

 

This solved your issue? What was the clog, that gross black stuff that's common on these cars?
How'd you get it out of the reservoir?

I'll have to try this. Which hose from the AST, the lower one?

 

i just recently opened up a harness and noticed that that plug coming off the water level sensor doesnt go anywhere in the harness except back to the motor. i just dont know WHERE exaclty the other end goes.

you say next to the ps pump but where? could you post a picture or something please?

 

Small update.
Tried the blowing air through the AST hose, no restrictions there.
Decided to add coolant to all 3 spots. filler neck on block, AST, and Overflow tank.
Added coolant till it was full at all 3 spots, while the car was running, burped it.

Alarm went away. For exactly 2 weeks. Today it started back up again. I haven't looked at the levels though.

This leads me to think there is a leak. Is that right?
Now I need to figure out where, and hope that it isn't the engine itself... I can't afford a rebuild right now.

Any ideas?

 

In the big fat fd3s cooling thread there is a diagram that shows the coolant path. I used it to find leaks on mine.

 

I'll take a look at that. I might go buy some coolant dye and a black light too.