Annoying Coolant Light/Buzzer
 

My add coolant light won't shut up! The radiator is full. I've checked five times. One time, with the motor idling, I opened the bleeder screw on the side of the radiator. Nothing came out but coolant. As soon as it was out a little bit, coolant started dripping out. There weren't even any air bubbles. The wires on the top of the coolant sensor are exposed, so I'm thinking it could be that it's going or gone bad. The temp gauge never goes over 1/4. It's an s4 N/A. When the motor starts to get warm, it'll stop for a minute or so, then start again. Any suggestions?

Its easy for air to get stuck in the system on the RX-7. You have to keep trying to top it off a little at a time. The sensor on top of the radiator needs to be in the coolant to shut the buzzer off. If you disconnect the wire from the sensor and ground it to the chassis, it will stop the buzzer, but only do this if you are sure the sensor is bad. Then replace the sensor ASAP and connect the wire back to the way it should be.

Wouldn't the air come out of the bleeder screw on the side if you opened it with the motor running? That happened once with my car. I opened it, and air came out for a few seconds. Then, coolant was coming out. Now, it's just coolant.

There is a thread in the archives that answers all your questions.

Yes bleed the air out of the system with that bleeder screw on the side of the radiator. You can also crack the coolant hose that is on the back of the Intake. You'll see it there are two coolant lines towards the fire wall.

Another thing that I have found. I use a turkey baster to squeeze coolant in there before starting it up.

Here is the bad news. If you continually have to put coolant into your system. this could be a sign that your coolant seals have gone bad ane you need a complete rebuild.

I changed the thermostat, lost coolant then, so I had to fill it up. Never since. I've just been bleeding the air since then. No bubbles in overflow tank. Coolant smells like coolant. Coolant is green.

Could just be bad wiring opening up on you. Follow the one-wire harness down as far as you can and look for any breaks (or fixing to break)...

Possibly be the sensor, too...

Check the warning system as per the instructions in the Body Electrical chapter of the FSM.

Bubbles may not "BE" in the coolant system as so many describe. It only takes on very small leak in your coolant seals to make a bubble form and eventually 'gather' where the sensor is in your radialtor.

Tell me this. Do you bleed the system and then you are able to drive a while?? Then after about 200-300 miles you have to bleed agian?

Did you read the Archives?? In it I describe how to bleed while the motor is hot. You touched on that technique in your first post. If you are driving and the motor is good and hot and the buzzer starts, you can then.....very......slowely open that blleder valve and your'll see steam first, then bubbles ore coolant and air gurgling out, then just a coolant drip. You have bleed the system at that time and the busser should be silent. IF you go for about 300 miles and this procedure has to be repeated then you may have trouble.

I tried to bleed it when it's hot, the only thing that comes out is coolant. Not a single air bubble. Just drops of coolant.

BERRY INTERESTING. Gotta be the sensor. does it ever shut up or is a constant??

It's quiet when it wants to be. If I'm crusin at 3K RPM, it'll turn on or off as it pleases.

try having the front end elevated in order to try to get the radiator to be the highest point. Check the connections per the FSM to make sure that your are getting a good connection. a short will make the buzzer sound.

I heard an interesting point that might have something to do with my problem. Is it possible that there could be too much water in the system? And that's it's evaporating in the cooling system, creating air which would set off the buzzer? Just a thought.

No, totally wrong physics. As your motor warms up the water heats and "expands". The extra pushes the radiator cap (the spring part) open and it goes into the coolant resivior. (the plastic white bottle that you add coolant too). When you shut off the car and it cools it draws water back in as needed.

If you say that you have all the air out of the system then you need to check the electrical connetions to see if it is not shorting on something.

take a length of wire and wrap it around a ground bolt and tighten the bolt down, next strip off a bit at the other end and shove it in the coolant level sensor connector(top of the radiator) and drive it, if the buzzer still comes on then you have a problem in your wiring, if it stays off then you either have a bad sensor or an air pocket still in the system. bad coolant seals develop air pockets in the cooling system while driving relatively quickly and no matter how hard you try you will not be able to keep them out.

I tried the coolant seal test. The one where you pop off the cap, and pull the EGI fuse, and crank the motor. No surging. Also no hot start problems at all.

I have a similar problem. But the coolant light only comes on when I'm idling or cruising at 3k or less. As soon as I wind the engine up a tiny bit it goes out. Could something like a water pump be causing that? Where is the sensor.

I just had a compression test done at Mazda, and everything was between 8 and 8.5 on their scale, which I think is good. Would dying coolant seals show up on a compression test?

Normally I would just do more research, but I'm test driving the car over the weekend and have to make a decision tomorrow.

mine did that before and it ended up that the coolant sensor got disconnected (the one on top of the radiator) so make sure that is fully connected before anything

1986 rx 7's
 

My 86 rx7 did the same thing when it was brand new.I took it back to the dealership and they added a contraption next to the radiator.Before this was done the service people advised me to remove the wire from the sensor and then place it back on thus resetting the system.Point is if you have an 86er with this contraption it may not doing its job properly.