ttmott

iTrader: (1)

Took my FD to work the other day (I do that a couple of times a month) and the Add coolant light and buzzer came on. Engine cooling system has worked flawless for years; temperature on aftermarket gauge read normal temperatures. After work started car to go home and it ran very rough and well below normal idle like it was missing ignition. Coolant light and buzzer again came on. After maybe 30 seconds it cleaned up and came to a normal idle. I shut it off and checked the coolant lever. When I removed the "fill" cap there was a lot of pressure and it blew some more coolant out; coolant was not warm or hot. Added water and got home; temperature maintained normal readings and when the AC was turned on it ran even cooler as normal.

Later that evening I took a look at the coolant level and it required about two cups to replenish. I even removed the wax rod heat hose to ensure any traped air was purged. Started car and it again ran very rough for about 30 seconds then cleaned up. Again immediatedly the cooling system pressurized when cold. I Drove it to dinner the next night and again comming home the light and buzzer came on.

Some observations:

• Normal first start smoke from exhaust; nothing unusual.
• Fans nominal
• Had all of the hoses, thermostat, water pump caps, etc. replaced about 20K ago
• Oil normal - no sign of coolant.
• No leaks except from the recovery bottle overflow.
• Running standard E-glycol anti-freeze at 40%; nothing changed here.
• Running temperatures are normal for Fl summer (185 - 215 Deg F)
• Fans cycle temperatures down as they always have.
• pulled the plugs after complete cool down; they were dry.

Baseline:

• Car 1994 - everything like new and well maintained.
• Original engine 128,000 miles
• M2 Stage III (big SMIC and duct, remapped ECM, M2 air box w/ K&N's)
• Grounds throughout the car updated.
• Never overheated since I have owned the car (3 years)
• Aftermarket temperature gauge.
• The car isn't abused; I do occasionally (ok more than occasionally) run it through the gears to redline and at the 15 PSI boost. Nothing new here...

I'm thinking may the seals finally gave up and the water jacket is being pressurized by the combustion - haven't yet checked the CO2 content in the coolant yet.... What do you guys think?????

Thanks

Pressurized

common problem, mine did the same thing, sorry i can't add more help, it's been 5yrs since i had my 7. i remember it was a simple fix though, so don't get too worried

Pdaddy43

iTrader: (3)

had the same problem 2 months ago and what i did was change my ast cap and took the lines off and blew them out with a air compressor one was pretty clogged so it was keeping the fluid in the ast tank and made the low coolant buzzer go on in the filler neck. good luck hope it helps

ttmott

iTrader: (1)

I could buy the AST theory or bubble in the engine block but the rough idle, I mean hardly idles when started then after a little while cleans up; as if the plugs were fouled...... The coolant level light/buzzer and the rough idle at the same time?? Seems something else is wrong....... I did change the AST and fill caps when the hoses were changed..

Six Rotors

iTrader: (17)

Time for a rebuild!

MR_Rick

iTrader: (7)

Pressure test your cooling system.

ttmott

iTrader: (1)

I think that's the right answer along with testing the CO2 content in the coolant. Will be dropping it off this week to get it done.... If the inevitable has happened, I will probably have a new short block with new components put together -

Is it more cost effective to purchase new Mazda short block complete or new parts and build up?

djseven

iTrader: (56)

The rough idle on cold start leads to believing it is likely a failed seal. However, replace the AST cap if you still have it and the line running to the overflow tank. Think of the simple cheap stuff before pulling the engine. If it has a rough idle on cold start you should see some smoke on cold start.

96fd3s

hello hello, you say you have a leak in your overflow talk!!?? this should be faily obvious if you indeed have a leak there.
As the coolant gets hot it expads - pushing the excess coolant into the overflow tank.
When the car cools down the the coolant retracts- the vacuum created by the retracting coolant should in theory suck the coolant from the overflow tank back into the engine/radiator/cooling system. This is where i believe you have your problem.

The coolant is not getting sucked back into the system as it should. This leads to low coolant levels and a coolant buzzer sounding. (since the excess coolant didnt get sucked back into the system as the car cooled down you will now get the "coolant buzzer" sounding as the level slowly goes down.. The buzzer will proerbly turn off shortly after startup as the coolant once again begins to circulate through the system.
Im sure this is the case especially if its the AST to overflow tank line that leaks.
Best of luck to you.

96fd3s

to add to my previous post - if its the actual overlfow tank that leaks - when the coolant gets hot and pushed into the overflow tank and leaks out. the car cant suck this lost coolant back into the system once again resulting in low coolant buzzer.

ttmott

iTrader: (1)

Clarification:
The expansion overflow tank has an overfill tube that dumps to the ground. Coolant was being discharged from that tube after I added additional antifreeze and water to the engine fill cap and ran it again.... The tank became too full and dumped to the ground.