I was coming back from a 1 1/2 hour trip when my low coolant light kept coming on around corners so I figured it was low. I filled it with a 50/50 of anti freeze and water like I'm supposed to and it went off. I filled it while it was running with the heater on and tried to pour smoothly so I would not add air bubbles as I have had before. a little while later (20-30 minutes) the low coolant light started coming on and off randomly in corners and on straights. not too many bumps so its not jumping around too much and the coolant is still full. whats going on here, it comes on for like 10 seconds and goes off then another 20 seconds then 2 seconds, etc. the time between it coming on is random. sometimes it does it a bunch of times close to eachother and then its fine for 5-10 minutes. I have looked at a few threads on this but none of them sound like this really and I have already gotten the air out of the system and checked for leaks everywhere. what could this be?

 

so there are no leaks?
and your coolant is full?
lookks like an elect. issue. i would first test the sensor to see if it is woring correct. look up the specs in the FSM. if the sensor is good i would next take a lookat the wiring.

 

Sounds to me like the coolent temp wire is grounding itself out. Check the wire ontop of the radiator and see if the shielding is shaved off, or if there's a bad connection to the sensor.
That's what mine was

 

ya, there are no leaks I can spot. definitely no coolant on the floor of my garage and I can't see any on any hoses or block either. I just checked it all again but still can't find a leak. it must be electrical. I will check the radiator sheilding first and then move to the sensor itself I suppose. thanks for the help guys.

 

a teeny little pinhole leak will cause this. coolant will get low enough to turn on the buzzer at certain rpms, but you only add a little.

i suggest you find/borrow/rent a cooling system pressure tester, pump it up to like 15-20psi, and let it sit for a while.

a leak like this can be small enough it wont make it to the ground

 

wow, that sucks. it doesn't seem to be using excessive coolant, the level has remained the same I am pretty sure. but if its a pin hole leak, it probably wouldn't spill much coolant. I already ordered another sensor so I will see if that works first. if it doesn't I will test the pressure.

 

If it's an S4, are you using the bleeder valve on top of the radiator when filling the system? If not, you will keep a nice little air pocket right near the sensor. Not sure for the procedure on S5's. Do you notice the coolant level in the overflow bottle going up? Either way, +1 on the pressure tester to check for leaks.

 

yeah mine was small enough not to really affect the level

 

coolant sensor issues are not to be taken lightly on rx7's i had a similar problem and was going crazy looking for a leak.. but there was no leak, it was burning coolant slowly... Take your time and if you absolutely can't figure anything out at all, and it is holding coolant perfectly and there is no loss in coolant whatsoever, just ground the sensor out so it will shut up, then youll need to make sure you check your coolant level at least once a week

 

I replaced the sensor and have driven it around 10 miles so far with no warning light. its still holding coolant and my engine is actually running a hair on the cold side. I tested my engine temp sensor(thermostat?), the one that gives the gauge the engine temp anyway (my bro told me which one it was), and it tested okay so I think it might be fixed. I need to drive it more to know for sure though. thanks for the help guys.

I'm working on a t2 rebuild now and I'm going to swap this summer I hope. I think I have a leaky injector anyway because I always rev up before I shut her off but it still floods when I go to start it the next time. I have to keep pulling the eng inj fuse and cranking to burn the fuel and then replace it and she starts right up. I'm going to try and get the rebuild done fast before my engine gets any worse. I have a friend helping me so it won't take too long I hope.