Inside the engine (i.e. engine rebuild).

 

well for starters....whats the T-stat? and yea the fans work...i dont get it. the car was running at 91 to 95 this morning and now its at 91 and jumps to 101 and back down to 91..i dont understand it. could that be an air bubble?

also what other signs are there that i can look for concerning o ring failure?

 

T-stat = thermostat

First off, 101 C is not a temp problem. In stock form, the cooling fans don't even kick on low until 105 C. Next, the problem is the coolant expelling from your car, not your temps. That's the problem you need to be addressing.

 

(Note: this post cannibalized by dgeesaman, content by scotty305)


7. Optimum Temps
65C (150F): too cold. According to service manual, EGR valve is non-operational below 150F, "to improve drivability when cold."
82C (180F): getting warm. Thermostat begins to open, circulating coolant through the radiator. Some coolant is still bypassing the radiator.
95C (203F): fully warm. Thermostat is fully open, not bypassing the radiator at all.
100C (212F): boiling point of pure water at atmospheric pressure.
105C (221F): getting hot. Stock ECU will activate fans to cool the car down. Fan speed will be low, or medium (if A/C is already on).
108C (226F): hot. Stock 93-95 coolant thermoswitch activates, changing fan speeds from low>> medium (or med>>high if A/C is already on) (switching to an FC thermoswitch will change this temp to 203F)
115C (240F): getting dangerous. OEM temp gauge begins to rise.
117C (243F): dangerous. boiling point of pure water with 13psi pressure cap.
121C (250F): too hot. OEM temp gauge will point to white line. Boiling point of pure water with 16psi pressure cap.
124C (256F): way too hot. Boiling point of pure water with 19psi pressure cap. Boiling point of 50/50 coolant mix with 13psi pressure cap.
127C (260F): way too hot. OEM temp gauge will point to red line.


A Mazda competition preparation manual, dated 1980, gives the following recommendations. Note that this is for a non-turbo 12A motor in a racing environment:
Warm the engine up at an idle speed of 2000-2500 RPM, until the oil temp reaches 160F (70C).
Recommended coolant temperature (outlet side): 160-195F (70-90C).
Max coolant temperature: 205F (95C).
Recommended oil temperature (oil pan): 195-230F (90-110C).
Max oil temperature: 250F (120C).


Pure water at atmospheric pressure boils at 212F (100C).
Pure water at 13psi (0.9bar) boils at 243F (117C). This is the standard pressure cap for many 3rd Gens after the cooling recall.
Pure water at 16psi (1.1bar) boils at 250F (121C).
Pure water at 19psi (1.3bar) boils at 256F (124C). This was the original pressure cap for the '93 RX-7s before the recall.
Pure water at 30psi (2.0bar) boils at 273F (133C). This is what Carlos Iglesias is using on his car. Many race cars use even higher pressures: I've heard that F1 teams run their coolant (pure water for efficiency) at 50 psi or higher (boiling point over 290F).
^^Remember, these numbers are for pure water; a 70/30 mix of water/ethylene glycol (standard yellow-green coolant) will raise the boiling point by about 8 F, and a 50/50 mix will raise the boiling point by about 13F.

i found this on another thread....

i think my coolant spill is coming from the overflow ....i have a 16 psi cap should i go higher? perhaps 19 or 20 psi cap?

 

I would try changing the T-Stat as stated before. I have seen them break and cause issues.

 

question..... i extracted some coolant out of the overflow tank and i noticed small little black stuff mixed in with it... is that just gunk or could that mean something terrible to come??

 

Ive been told not to go higher psi cap than stock or it can put extra pressure on your seals.

Did you bleed the coolant when you put the AST in?

 

That's fairly normal. The vent hole in the neck of the overflow tank gets in some road dust and crude over time. It's a good idea to flush out that container when you do your coolant flushes.

 

As was stated, I'd begin by changing the t-stat. Put in a 180 degree. It dropped my temps a couple degrees right off the bat.

Secondly, I agree with the o-ring failure diagnosis, unfortunately...If that's the case, you're going to have to pull the motor, separate the rotor housings/irons, and replace the coolant seals (assuming nothing else has been damaged).

Also, you should be running a 13 psi cap, NOT a 16 psi...Again, as was stated, check to be sure your radiator fans are coming on properly.

However, what typically happens as a result of an o-ring failure is coolant forces its way out through the overflow...Unfortunately I can say that I know this from experience.

What happens is the exhaust forces its way past the bad coolant seal, and gets into/overpressurizes the coolant system. The path of least resistance for the coolant to take is the weep hole in the top of the overflow. After all, the overpressurized coolant has to go somewhere, and that's typically where it goes to and leaks from (assuming you have no leaks elsewhere). Then, when the motor cools down and draws coolant back from the overflow, it's no mystery why the coolant level is low and the coolant alarm is triggered.

I, too, share 82-84 degree temps while cruising, and 85-87 in traffic (even on a hot day). Investing in a Fluidyne radiator, 180 degree t-stat, and PFC (adjusted my fans to come on at 180) was the best thing I ever did for the car.

By the way, do you have any problem with hot starts? Does the car like to start and stall a few times before it stays running (If it does that's because coolant is getting on the spark plugs, and coolant doesn't burn)? Are you blowing lots of white smoke during hot/cold starts?

 

While road dirt getting in there is a possibility it isn't a correlation to your coolant loss unless it's getting trapped under the radiator cap seal. Typically when you find the black oily crusty debris in the recovery tank it indicates carbon that was once in the coolant o-ring groove being pushed into the coolant system by combustion gases. Since you changed your coolant (twice) replaced your cap and (thermostat ?) not sure on that one,used your funnel to burp the system and get all the air out of it (always best to do this with the heater on full) and made sure the level in the recovery tank was no lower than the low mark when cold ( it will be just over the full line when hot and you should be able to see it move to these marks under these conditions. If it is going to the full mark and staying there when cold you have a leak in the cooling system that is preventing it from drawing the coolant back out of the recovery tank. The black stuff you mentioned has a tendency to get under the radiator cap seal when being pushed into the recovery tank and prevent the cap from sealing when it cools down and won't pull the coolant back into the system. Since your temps aren't that far out of line for a front mount inter-cooler (without proper radiator ducting) your main goal is to get all the air out of the system, let cool top off, make sure the recovery tank is filled to the proper level cold, make sure your cap seals properly and that coolant moves to and from the recovery tank as it should when hot and cooled off. If it's not working right then after the car heat cycles the first time it will then have air in it and won't maintain the proper temps after that. Moves up and down with spikes. Hope this gives you a place to start, and helps isolate the problem.

 

yea i was unsure about the whole changing the T-stat and what methods do you recommend finding the leak....my temps have been 80 -83 with coolant...ater some coolant is lost from the overflow tank my temps spike to 96 and again to 106...but drops down to 90 again.. i did some ducting work and i have to say it was the best idea!! idk why i didnt think about that....thanks!

now what causes coolant not to return to the system?

 

Coolant getting pushed to the overflow tank is definitely a symptom of o-ring failure. Basically exhaust gasses from a combustion chamber are escaping into the coolant system and overpressurizing it. My car had the same sort of symptoms yours had with the temperature going up and down on the PFC and doing the champagne test (search forum for this) showed that I definitely had o-ring failure. Another symptom of exhaust gasses bubbling through the coolant system is black goo on the overflow tank dipstick and sticking to the insides of the overflow tank.

 

ok....heres something that happened this morning

i started the car this morning after 2 days without it started and it was spuddering.....it was at 700 rpms right at the start and it seemed like it was gasping for air and i noticed a little bit of smoke but couldnt make out the color in time before it was gone.... my o-rings are shot right......

 

ok so i just did that champagne test and here are my results..at about 55 degrees i would see medium sized bubbles popping up 2-3 seconds at a time... once it reached 84 degrees i would see the same sized bubbles if not bigger 15 seconds at a time but i did not see any tiny bubbles as you would see in actual champagne...does this mean my o-rings are ok? also i checked the bottom of my rad. cap and it was pretty slimy but no dirt. im thinking it was slimy due to the coolant being like that.....im getting my cooling system pressured checked today do you guys have any other ideas as to what it could be?


thanks

 

True of a completely stock FD. Mazda changed from 16 lb to 13 lb as a TSB IIRC, as the stock rad hoses could not take the pressure. This is especially true if they are old hoses.

Replace with some high quality silicone hoses for the rad, and replace all the other coolant hoses with quality new hose, and 16 lb should be fine.

Personally, I am running 16 lb with 75/25 water/coolant. Temps have stayed pretty good.

A few weeks ago on the dyno coolant temps never got above 95c.

This is on a v-mount setup, koyo rad, stock fans.

 

Have you tried a hydrocarbon test?

i had a similar problem after buying my FD last year. after doing all the basic cooling mods and tests for overheating..the one that sealed it for me was the hydrocarbon test. the test came back positive for exhaust gasses in the coolant. i subsequently pulled the motor out and found a small crack in one of the water jacket seals. the leak was very small and the temperature only rose drastically when driven hard or stuck in traffic for prolonged periods.

i hope for your sake its not the o-rings...good luck

 

For me once it got past 55 degrees C it was a constant stream of bubbles probably 1/4" in diameter. Once the temp was about 80C it looked like the coolant was boiling. So if the bubbles stop after a while you may not have a o-ring problem but as mentioned in the previous post a hydrocarbon test will give you a definitive answer.

 

how is the hydrocarbon test preformed?

 

with a hydrocarbon "sniffer" i beleive. I think you would have to take it in for that.

 

It seems that one rotor is getting coolant during heatsoak.When you try to start the car the spark plugs of the rotor are wet with coolant,so until they dry, the car runs in one rotor.That might explain the spuddering and the smoke.Let the car heatsoak,and the next morning remove the spark plugs from each rotor.If they are wet,time for a rebuild...

 

Basically, its a glass tube filled with a "special" mixture, normally dark blue in colour. The glass tube is kind of like a big eye dropper, once filled with the special liquid it is placed over the filler cap to the cooling system and it
"sniffsin" the gasses from the cooling system. if there is carbon in the gasses it tuns the dark blue liquid to yellow within a few seconds.

as said before, a good radiator shop should be able to do it. most often its free of charge, but if not, its very inexpensive.

 

ok heres the update

-I got the pressure test...........passed
-i did the champagne test........passed
-I did the Hydrocarbon test......passed that too


the car is still acting up. i have to bring a bottle of water with me everywhere i go just in case

do you guys have any more suggestions as to what i can do? i already got a new cap and thermostat and i ordered new hoses already and i eliminated my AST.

 

anyone....??

 

Install back your AST

 

what about you oil cooler"s"...??