I changed the rad, thermostat, water pump and fan and the rad cap. It can sit idling for hours with out over heating. The temp guage needle stays low 1/4 way from c. I can take it for a drive with no issues untill about an hour into the drive the coolint light lights up, i rev it up and the coolint light shuts off. I can keep driving with out any problem then the temp guage starts to creep up till it reaches the H coolent starts come out of the reserve tank.

The car has 154,000 miles on it. It runs really good no leaks anywhere. Starts right up everytime.

 

Did you try pressure testing the coolant system? This could find an internal leak and if not then you have peace of mind at least. Maybe one of the belts is slipping, did you get a new water pump belt with the water pump? Did you replace both rad caps if you have two? Did you make sure to put an OEM mazda thermostat in? (Stant ones are known to be faulty for the rx7.)

 

i just went over all this in my car...check the following


clutch fan: spin it with your hand fast..if it moves for longer than a second or 2 then replace it

efan: make sure its the right size and has proper ducting

water pump belt: grab the pulley where the water pump is and spin it with your hand, if you can spin it either way with your hand, the belt is too loose

belt: check that the belt isnt too badly worn and that the rubber isnt hard on the side where it contacts the pulley system

thermostat: make sure you have a 170-180 degree tstat

leaks: even the smallest leak will lower the psi in the system obviously and therefore lowering the boiling point in the system causing it to overheat....check the heater core lines that run from the engine block to the firewall on the driver side then check the firewall to the radiator on the passenger side, if you have a turbo check the feed/return lines for coolant leaks, also check the water port on the back of the housing if you have one...

when fillin the system with water: make sure you top it off at the lowest point, cap it off, then move to the highest point in the system and top off the coolant there and leave the cap off...inside the car turn the heater to full blast and start the car...let it idle for about 15-20 min to purge the air from the system...keep adding coolant to the highest point and never remove the lowest cap etc...when you are done replace the cap and drive it around...let it cool...and add water if needed

overflow bottle: fill water to the max line, this will help you to understand whats going on with the system...if there is added water then there is a leak somewhere or your radiator cap is broken

radiator cap: if its old...replace it....the cap is what helps keep the system pressurized so your boiling point is raised....therefore allowing you to run cooler

often overlooked: engine bay temps...if you have a turbo, esp a big one like i have...you need to get that heat out of the engine bay else your temps will stay high no matter what you have going on...so a turbo blanket, exhaust downpipe wrapping, no exhaust leaks inside the engine bay, etc...turbos can get super hot on the highway and cause more heat than you can imagine....this is my issue with my car when it gets too hot these days..

my idle temp is 165 degrees, highway when its cold out, 180 degrees tops, when its hot...210+ if i go over 2500 rpm

 

Thanks for the replies. The belts are good. I'll try and turn on the heater at full blast while filling it with coolant. Thanks again. I'll let you know if this helps the problem.



Should I be worried about the engine in any way...I mean the coolant seals or something.

 

yes if you still overheat after checking everything i described...those are the first steps......

 

Done what you described this past weekend. Thermostat and rad caps though not Mazda they are new. I found a leak in the hoses at the top of the intake and fix them. Drove it for a while the temp stayed well-below the 1/4 mark. (I found that kind of strange.) I took it on the public roads and then took it on the highway. After a while the add coolant light came on and off couple times then the temp began to rise slowly to a 1/4 ways but no more than that. I parked the car left it alone over night. I took the car to work for the first time. The whole way to work, (1 1/2 to 2 hr drive to and from work) no issues until i got to the exit of where I work the temp began rising again. Parked left it alone. On the way to home Mostly highway no problems. As soon as I hit stop and go traffic it began to rise again. Pulled over and waited for it to cool. Started out again and no issues at all no over heating even in stop and go traffic.

I don't know what else it could be other than a rebuild.

 

I'd revisit the thermostat before giving up.
The symptoms you describe can all be explained by a wonky thermostat and I don't see how the engine internals could act so randomly- bad coolant seals don't get better when they feel like it and worse when they don't, they just fail. And when they do, you see smoke- lots of it.

Just last week my car was acting exactly like yours...temp was randomly going up and down, unrelated to load/speed/ambient temp.

Naturally, my local Mazda dealer didn't have a thermostat so I went to NAPA.
The part their computer insisted was right wasn't even close and I had to return it.
The part # for a third gen thermostat got me exactly what I needed, an exact fit and it had the jiggle pin, which Stants lack.

For $16 it's worth a try.

 

Hmmm....makes lots of sense. I bought the thermostat at an Autozone. I'm going to try and get the right thermostat.


Thanks, much appreciated...may the rotary Gods look upon you and bless thee.

 

Well Its been awhile since I last posted on this issue but I managed to solve the problem.
When I bought the car it had overheating issues already. The oem radiator was in the car and it had no ho to connect to the reserve tank. The filler neck has the hose for the reserve tank. Anyway I replaced the rad in hopes that it would solve the problem. I stalled the new rad and connected everything just the way it was. Only the new rad had a connection for the reserve tank. I blocked it of and went on my merry way still over heating.
So after being stuck on the side of the road in the rain for an hour waiting for it to cool. I decided to connect the reserve tank hose directly to the rad. and block off the hose that came from the filler neck. Problem fixed. no more over heating.

 

Wouldnt that be a sign that the filler neck cap is bad?