Ok so as you guys know i live in South Tx and lately the temps have been steady at 100 degress everyday!! I have noticed something with my FB that i am now concerned about. When i have the AC off she is well below the midway point on the temp gauge (but i am sweating my ***** off). But once i turn her on (the ice cold AC) and it is 100 degrees out side during the day the neddle goes to 3/4 of the way up. What do i need to do to stop this from happening (its a little unsettling to see your temp neddle at the 3/4 mark!!) ? She has the stock radiator still and i have yet to replace the new mazda thermostat and water pump i bought recently. What would you guys recommend i do? She is an 82 GS. And no she has NEVER overheated!

 

Install the new pump & thermostat, flush & fill with new coolant, and check your radiator fins to see if they are bent or clogged with bugs/dirt. It's a good idea to check your hoses before you drain & replace the coolant.

I agree that 3/4 on the gauge is a little too high for comfort, but it could just be a combination of the high ambient temperature with the extra work the engine has to do while running the a/c. I would keep a close eye on it. Does the temp go down if you are moving, or does it go to 3/4 and stay even if you are sitting in traffic?

I was in San Antonio for a week during the summer of '90. It was 85 degrees at 7:00am every morning I was there. But it was a dry heat, lol.

 

Fab up some air ducts to blow the cold ac air back in the engine bay! lol. Actually most cars I've ever owned did the same thing on a really hot day. As long as shes not too hot u should be okay. Do you have the right amount of coolant in her? Some people just and water w/o antifreeze, not good!

 

E-fan or two.

I have a tempo fan on mine, doesn't go past 200 as controled by a Volvo themo-switch. Of couse I don't have AC, but get good efan with shroud (ford's seem to be popular) and maybe a smaller "pusher" fan from a mercedes 190e or something similar.

 

Actually plain DISTILLED water with a water wetter solution IS good, cools better than an antifreesze mix.

Thing about what ANTIFREEZE is for...

 

Man you don't know about hot until you come to south Louisiana, humidity is a bitch.

 

adding anti-freeze also raises the boiling point of the water, due to colligative properties

 

You are partly right.. It is also called COOLANT.. Why is that?????




I'll tell you why.. Normal water will boil very easily turning into vapor. WHICH IS VERY HOT and can mess up your engine.


So in hot climates where it DOESNT freeze, i would run 80% water 20% coolant.

this will keep the water from boiling but have better hear disappation then 50/50

always use destilled water!


-Zach

 

The A/C Condenser is in front of the radiator, and is emitting a lot of hot air. That hot air is flowing directly into the radiator.

IF you have some time to kill, I have found that spraying self expanding foam in the nose of the car to seal up all the little cracks and seams in there so that air can ONLY flow thru radiator and oil cooler will cool the coolant and oil 10*F each. Howz that for a runon sentance?

If the coolant system has not been Prestone Super Flushed in the last 2 years/24,000 miles, now is a good time. Could be blockage / rust scale in there.

+ what everone above said.

 

Coolant is a misnomer... the pressure in the coolant system is what keeps the water from boiling. There is a formula that I don't have time to find to explain the difference of the boiling point for a given PSI.

The only real good reason to use antifreeze in a hot climate is the oil for you pump and that ONE day it drops below freezing so your engine doesn't crack.

I guess another reason would be so you don't have to explain why you're just running water with wetter.

 

Get a new radiator. You have 23 years of rust and scale inside of that thing. It's $200 for a new rad from BDA, think of it as a $200 insurance policy. I'm not even going to start my FB again until it has a new cooling system in place.

 

I understand why cars cooling systems are under pressure. but BOTH increase the boiling point of water.. Any time you add anything to water you increase its boiling point.

Go for a hard drive in AZ with 100% water and you will understand why i recommend 20% coolant & 80% water in warm weather. I have boiled 100% water before and the pressure cap was functioning just fine.


I have also heard that some water pump's expect coolant there for extra lubracation? (prolly not relevant to RX7s)



EDIT:

Thinking about this, it is probably because the cooling system was not up to spec and the water was getting hotter then it should have gotten for the pressure of the cap..

Either way, the coolant helped keep it from boiling.

 

I'll take your experiance, and it is good that you recommend some coolant.

I understand that adding things to water raises the boiling point.

The lubracation... addressed in my last post.

I do live in the NE so I guess that's why I never had any issue, my temp had never crossed 210* even sitting in traffic on a 90* day up here.

I do, now, run antifreeze because it sucks having to change "coolant" with the seasons.

 

100% Coolant?

I run straight coolant with minimal problems on the race engine I have in my fb as a DD. Doesn't go past the half way mark in a 100* day.

The BEST Fans are the stock fans. Why do you think they run so cool when stock?

I'm looking into an electric fan so I can run an airconditionaing system but I have yet to find one that actually cools better than the stock one and looks like the right size. (Not oversized)

With all that said. I know nothing about boiling points so don't jump too hard. But I DO reccomend straight coolant NO water.

 

Some part, or more than one, of the cooling system is ageing. There have been several good suggestions here. I would start with the flush and fill, new thermostat, cleaning the fins on the ac condensor, radiator and fmoc. A can of water wetter will help too.

If that doesn't take care of it, look into having the radiator redone professionally.

3 things that haven't been mentioned: is your undertray installed and when running the ac, is the climate system set to fresh air or recirc? Recirc puts less load on the ac system, once the interior is cooled down. You may wish to have the ac checked. It might be low on freon and working harder than need be.

 

Antifreeze is what killed my 13B 4 port. The motor sat up for a while with minimal running (2 or 3 times a month), and the antifreeze slowly ate through my housing.

Notice the light where it isn't supposed to be...



Right now, on my new motor, I am running 100% water with a 180* t-stat and the stock clutch fan. I plan on adding Water Wetter or something of that sort soon.

 

Radiator is $110 from radiators.com. I've installed 2 and both cars are cooling well.

First RX-7 I drove was a 1980 rental in Savannah and the AC was cold and the engine temp stayed at 1/3. The weather was punishingly hot.

 

I use 10-15% coolent/anitfreeze The rest H20 and top it off with purple Ice, It works great for me.

 

While there have been many helpful suggestions in this thread, no one has even mentioned checking the fan clutch. If the fan clutch is not holding as tightly as it should, it will will let the fan spin too slowly, thereby not pulling enough air thru the rad.
Fan clutches can fail 2 ways. They can lock up, and spin the fan at 100% full time, or they can loose tension, allowing the fan to spin slower than designed.

 

Clean85owner'd dad has mentioned if you put a bolt all the way through the fan and the pully it is on, it will spin the same speed as the engine. I don't know if I worded that correctly. It prutty much locks up the fan with the engine so it spins the same rpms as the engine.

 

Totally locking the fan clutch will cause excess drag on the engine, robbing both HP and MPG. This "solution" should only be used as a temp method of solving a totally non-functioning fan clutch. It can also place extra strain on the water pump, causing premature failure of the bearings/seals.

 

I forgot to mention he said it was more of a last resort option. He didn't recommend it for a daily driver thing. I just didn't think when I typed that, that's all. lol

 

Holy crap $110 BUCKS!!!! THATS CHEAP!!!! Wow i may just do that. and they are direct bolt on or do i need to modify it to get it on there??



All you guys rock!!! Thank you all for the help thus far!!!

 

I have heard that 90% of the radiators.com units are direct bolt ons, while a few had to be modded very slightly. Luck of the draw, I guess......

 

I agree with most that's been said. If the rad is that old, undoubtedly you have some blockage going on due to setiment and age. Forget about having the rad rodded or professionally serviced. That would run you between $50 to $75 alone.

I'd get the new rad from radiators.com, make sure that the undertray is properly secured, and check the mouth or front opening to ensure that any places where air can escape are properly sealed. Redirecting more air helps a TON.

As far as water to AF mix, I've run everything from straight distilled water with a bottle of water wetter to my current setup of 20% AF and 80% distilled water with a bottle of WW. I added 20% AF back into my system on Steve Kan's recommendation since many of the motors that he's torn down where the owner ran straight water had an extremely high level of internal rust and corrosion. He suggests no more aggressive than 30% AF/70% water, but here in Phoenix I think going 80/20 is acceptable.

Just my .02! Post your results once you get everything installed.