Hi guys, rookie on the site and new owner of a 93 FD... love the car. Added water wetter yesterday, checked all levels, everything is ok. Start the car this morning, add coolant and beeper sound is on until car was warm and it stopped... what went wrong??? Thanx ahead of time for the cues!

Chucklate

 

you need to add more coolant fill the neck up to the top

 

You need to check the caps on the Filler neck and the AST and make certain they are tight and have a good seal, because the filler neck is one of the highest points in the cooling system if the lid does not have a good seal or the AST is loose, coolant will run down into the overflow tank located under the passenger side headlight. If the caps are sealing well, check the lines to the filler neck, the ast and the radiator for leaks.

Here's a thread on the cooling system.
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/big-fat-fd3s-cooling-thread-571088/

I had the same conceren a week after buying my first FD, come to find out I had the AST lid partially open and I kept adding coolant to the filler neck and it kept running into the overflow tank. Eventually it ran all over the floor. Then I found the problem. Overfillinig the overflow neck doesn't always fix the problem.

 

Burp the system and continue to top it off

 

There's also a coolant level sensor near the front of the Filler Neck. Make certain there's a wire that's connected to it. If it's not, you'll always get the alarm sound and coolant light no matter how much you fill it.

If you don't see a wire connected to it, try to find the missing wire and solder it to the connector.

 

Finally had a chance to investigate this problem with my coolant light this weekend. It all kind of started out of the blue, I had been driving for a while and was just around the corner from work... and my light came on. That has happened before, and usually I just top off the neck and I'm all set. Tried that before I left for home, but no affect.

I reluctantly drove home, watching my temps the whole way... and everything appeared fine. I verified a few things when I got back from work... made sure that all hoses were tight and that I was keeping the coolant level about an inch or so from the top of the radiator cap. The level in the overflow tank is about: E --------x--F , when the car is cold.

So, I went ahead and ordered the sensor, and installed yesterday. Unfortunately, about 10 seconds after starting the car, the BEEEEEEEEEEEEP, kicked back on and the ADD COOLANT light came on. Whatever I did didn't seem to make much difference. I've been reading the forums, but no one seems to have the same solution to the problem across the board. Some say bleed the system, some say it's the sensor, others a bad ground. It's a new harness, so everything should be grounded well. Unless some wires weren't properly hooked up after the new steering rack, and water pump were installed. But that was almost a year ago, and this is a new occurrence. Temps are fine, so far as I can tell... cruises at 86-88... 91-95 when your getting boost happy... higher if you are really going nuts. Though, since the light came on, I've been very gentle with it.

I really thought for sure the sensor would do it, now i don't know where to start. The electrical system on this car is so flaky... that I really hope it's not some transcent circuit somewhere. All the other gauges, lights, stereo, ecu are behaving fine...

I'm looking for next steps.

 

my coolant light is perma on eventhough the system is full. I just check it ever so often to make sure. it's always full.

You could run a new wire from the sensor to the ecu. I've been to lazy as I've kept a close eye on the operating temps. Sounds like the wire's not correct somewhere through the system.

 

Yea... I'd rather not hack the system just yet. I've already had to do that in a few instances... and soon my car will become a wiring nightmare. Plus, with all the overheating issues I've had in the past, I want to make sure I can always be warned if the coolant level is too low, incase there is a leak. I ususally check just about everytime I go out... but you never know.

 

there have been many with loose or broken wire behind power steering pump down by the spark plugs (a black 18-20 gauge wire). an open there causes the coolant level to beep. search, there are other threads on that.

 

Ok.. I'll take a look back there and see if anything is plit. I think I know where you are talking about. If it's the same thing, I remember that being quite split a while back until we replaced my engine wiring harness. But, I'll look anyway.

Dave at KDR suggested that it could be a bad radiator cap... here are some thoughts he had:

"...what a rad cap does is under pressure allows coolant over to overflow tank but under vacumn will not allow coolant back...so add coolant light keeps coming on...real famous with pettit tank and stant cap..not so common with factory cap..but has been seen...so I would repace cap first...the other leak that is common is the overflow hose from tank to engine has a split in it...so it only leaks while driving...but whne sitting you never see it...and then when the cap opens to pull a vcaumn it leaks out that hose..so check that also...."

Can I pick up a new radiator cap anywhere, like AutoZone or Pepboys? Just one specific to my car, or is this a mazda only thing. Also, are there any differences in say, pressure sensitivity, or something like that. I'm not familiar with this, so bare with me.

Thanks.

 

How many miles do you have on your motor? When i ran into this problem, I check everything people have mentioned, but nothing worked. I brought it to my mechanic, and it turned that i had been leaking coolant into my exhaust, and even though the level didn't go down much (i thought it was full all the time), i had a leak into the exhaust.

 

Only have 25k on the motor.

As far as caps go... I'm seeing several different options. 1.2bar, 1.3bar (greddy), and the factory. Then I see there is a 13psi and 16psi OEM version, and a large and small neck.

 

You filled it before starting. It stops buzzing after it's warmed up? So the sensor would be submersed in coolant the whole time.

Because the buzzing stops, I don't think its the wire behind the power steering then.

Start your car with the coolant full and cap off. note if the coolant level drops below the sensor. of course put the cap on when the coolant begins to expand.

 

I'm pretty sure the first thing I said was check the caps for a good seal, the coolant thread I linked to at the top of the post hass info on caps...

 

Hey guys. Just put on a brand new Mazda .9bar rad cap... started up the car... about 5 seconds or so after starting the light and buzzer came on. When I put the cap on, the fill level was about an inch from the top. It didn't go down much at all after I looked under it again. Didn't run the care for more than 2 mins... but I assume it wouldn't have gone off if I had.

So, now I've replaced the cap AND the sensor. I checked the wire down below the power steering and spark plugs, it's a single wire with a white clip connecting it from what is probably the harness. Seems ok. I don't know where else to look or what else to do at this point.

The only thing I haven't done yet is to bleed the system. I'm sure there is a good post on that on here... from what I have heard - you disconnect the hose from the UIM, near the throttle body... and just put a bucket under it. Do you do this with the cap off, and just keep adding coolant/water?

Thoughts?

 

https://www.rx7club.com/showthread.p...power+steering

in this thread they talk about a short between the coolant level sensor and the ECU.

any bare wires between the level sensor connector and the harness? I had a few repairs done on that wire.

I doubt if it's anything with the coolant level itself.

 

if your coolant sensor is good and your not loosing any there has to be a short somewhere. G

 

Yea... it's starting to seem like that is more likely the problem. I'm heading to the shop tomorrow to spend some time trying to trace the problem in the wiring.

Thanks for all your advice!

 

Did you check the AST cap? That's where my problem was...
http://www.robrobinette.com/flush.htm
Purge instructions are here....

 

I've actually had the AST removed for about 6 years... so, it shouldn't be related to that problem. We removed it during my first rebuild, and was told it wasn't critical - so we never threw in an aluminum tank.

 

Problem fixed. Turned out to be a broken wire that goes into the engine wiring harness, down near the plugs/behind the power steering. I looked there a bunch of times with a flash light - but didn't see a problem. Dave at KDR went right there and took care of it in about 5mins. Heh.

 

Good deal and thanks for following up on the thread!

 

If there is no air in your system, and the caps are in there proper location and the seals do in fact seal tne there is no reason not to fill the the water pump neck up to the top. Your recovery tank level is ok but could be put to the full mark (when cold). When topping off my system I top off the AST first, place the cap on (all the way) then top off the filler neck. If there's no air being introduced into the system then should always remain at this level.