FD sporadic Add coolant light
 

I recently bought my FD and have been coming across an annoying issue.
My add coolant light will turn on at times and will turn off soon after (light only, no buzzer). It will do this a handful of times while driving.

I removed the cap and checked the highest point in the coolant system (not sure what it's called, sorry) and it's all topped off.

Could it just be a sensor? if so, which one?
I recall that RX-8s have a problem with the coolant level sensor going bad after 80k+ miles, which would cause the coolant light to come on permanently or on and off randomly, but I didn't think it would be a problem for 3rd gens.


https://cimg0.ibsrv.net/gimg/www.rx7...7b86f259ff.jpg

Look straight down from the overflow hose on the filler neck (where you should have checked the coolant level). You'll see a black hex-shaped head with a single wire lead. That's your coolant level sensor.

And do you see any temp spiking or gurgling/boiling sounds from the engine...particularly after shut down?

No strange gurgling sounds. My PFC will arrive tomorrow so that will help me determine if the temps are indeed spiking.

Another thing that I noticed is that the oil pressure gauge moves around a bit when I take off from a stand still.
Is it supposed to be a dummy gauge like the temperature one? Because it moves quite fast but always ends up going back up to the middle.

I really appreciate the help by the way.

Yeah it moves. I try to keep mine below 60 or so until the car warms up. :)

I think he's asking about the gurgling sound because 90% of the time, your symptoms are the AST acting up. I see you have an aftermarket one which is good, but maybe check the cap and around it for leaks. Its the aluminum bottle/tank by the battery.

EDIT: don't touch it when it's hot!

Are you saying that one can control oil pressure?

And my oil pressure gauge on the cluster moves around when it's already warm. It will be in the middle while idling at a light, but once I start to get going again it drops quickly and goes back to the middle once I'm back in motion.

My AST tank isn't leaking or anything. Although I tried opening the cap but when I twist it it won't come off the tank. It's weird, Im not sure what's holding it back

The oil pressure sender is on the right/passenger side of the engine just below the oil filter pedestal. It has a single spade connection that tends to get fouled over time from dripping oil/dirt when the filter is changed. At times, like at idle, there's little indicated oil pressure because the signal can't get through the poor connection. When warm the oil also has a thinner viscosity and tends to produce a weaker signal. Clean it and see if your indicated oil pressure improves. Sometimes it's the sender itself.

You really should get a copy of the Factory Service Manual (FSM). Downloadable for free in the FAQ sticky at the top of this page.

The power FC came in and I've been monitoring the water temperatures.

No more turbo hesitation :)

:icon_tup:

Temps will naturally spike a bit after periods of hard boost. What isn't natural is temp spiking while cruising steadily down the highway. If you see that type of spiking I would recommend a pressure test of the system.

coolant light
 

Might consider checking the tach connector and gauge connectors in the cluster,could be loose or corroded

I've been monitoring the temperatures with the PFC and this is what's going on:
During high way cruising the light never turns on, it's during stop and go traffic that the light comes on and I see a spike in temperature in a very short amount of time (86c-98c in a minute) shortly after the light turns off, the water temperature drops back to around 86c.

I purged the system (or thought I did) and I still have this problem. What else could it be? I'm thinking that it has to be air in the system

It might be. Have you burped the system after replacing the coolant?

Have the cooling system pressure tested.

I thought I had burped it. I used one of those big funnels to get the air out.

I pressure tested it and found that pressure slowly drops. I inspected for leaks but couldn't find anything. I was looking for a hissing sound that would be caused by a puncture in a hose or something but nothing.

Could it be internal? Like somehow in the block? Although I don't smoke at all.

I did hear some gurgling noises after shutdown today. I pulled the "vent" lever on the AST cap and the gurgling got a lot louder. (I have a feeling I introduced a ton of air into the system by pulling that lever. IF that's the case, I feel like a complete idiot).

Well, the engine is at 136k miles (Yes, original. Never rebuilt)
so it wouldn't be surprising if it's the coolant seals...BUT..
does that mean that my temperatures spiking are actual coolant temps going up, (due possibly coolant being lost in the housings) not just water vapor hitting the sensor? or could it be that air is being introduced from within the block (the bad coolant seals) because like I've said, the engine doesn't smoke at all.

By the way, this engine is incredibly healthy. It runs great and starts right up, hot or cold. pushing 300whp @12psi on a conservative tune with no problems