I don't think this is normal for an rx7, but let me on some feedback. MY 91 rx7 convertable is ok when i drive it under hot days (virginia can be a beast for hot days). The temperature gauge shows its running normally (you know, the needle is in the middle of Cold and Hot in the dash). But it seems when i hit the A/C, the temperature rises. The needle on the temperature gauge goes from being in the middle to 3/4. (like it rose like 20-30 degrees). Whether i be at an idle or going 80 down the freeway. But seems to happen in humid and hot weather. You think the outside temperature is really putting stress on the rx7? when i turn off the A/C the temp returns to normal.
Also note, i replace the old radiator (which was the original by the way, 14 years old) with a steel radiator. My old radiator maintained the temps before it cracked

 

I have the same problem, if its hotter than 90 outside, the ac causes the car to start to overheat. I have the steel radiator too. I just dont run the AC when its that hot, i've read that anything over halfway is bad on S5 temp gauge

 

jsut on a side note... where does the temp gauge get its reading? the water thermosensor?

 

from the sensor next to the oil pressure sender under the oil filter

 

You have a cooling capacity issue. Are all the ducts in place? Is the RAD flowing sufficiently? Is your T-Stat good?

 

what? lamens terms bro. I have a higher experties on how to put a computer together from scratch then a rotary engine. I have no clue what a RAD or t-stat is. sorry

 

take off you rad cap and start the car. make sure you dont have a constant stream of bubbles coming from the radiator... if you do, then you have a bad coolant seal and that would explain why you overheat when under load. i hope you dont have anything like that going on though. i wouldnt wish that on anyone, unless they sucked.

 

rad=radiator
t-stat=thermostat(if it hasnt been replaced in awhile, replace it with a 180 degree one)

 

I've had problems with steel radiators.
Aluminum is the way to go. You get what you pay for. Either source a good used aluminum radiator from ebay/parts dismantler or upgrade to a koyo/fluidyne/pwr......
And, replacing the thermstat every couple of years is good maintenance.
Also, check your fan clutch. The fan should spin freely when cold. But, it should show resistance when the engine is hot(and off to keep fingers).

 

I think it might be the fan clutch. I have delt with those before. And as far as the bubbles, i know about that too. I took the time to make sure there was no bubbles in the radiator.

 

It is not going to be his fan b/c he is not over heating on idle. It is simply a capacity issue. Only replace your T-stat with a Mazda OEM one! An auto parts store 180f T-stat will result in overheating. As stated it could be a cooling seal blow. Best way is to use a coolant compression checker and pressures the system to 13psi and see if it holds. This is covered in links in the FAQ. If it is not coolant seals it is ducting issues, clogged RAD, Bad mixture, low coolant, Bad pump. A bad T-stat will result in overheating all the time but is still a good item to replace.

A full list of obviations is found in the FAQ sticky on this page. Please read it.

 

It sounds to me like the steel radiator just isnt up to the task, especially since that happened to both of you, and it didnt happen with the stock rad. If it was coolant seals, he would be loosing coolant which he didnt mention. Plus it would still cool while it had coolant.
Also, if it overheats when you are moving, its never a fan clutch as the fan only cools when you arent moving.

 

i've been having this problem this summer also. from what i've read and the responses i've recieved from a similar thread of mine, the fan in front of the A/C condensor is not turning on. that is why it happens when the A/C is on and goes away when its off. i'll be upgrading my rad and trying to fix this fan (if there even is one) either way it has to be fixed. i'll let you guys know when i finally fix this problem

 

A few questions. How long have you owned this car and have there ever been any other cooling issues? Your radiator has a center section, referred to as a core, and end tanks. The tanks may be the steel you're referring to, although I think that's doubtful. At any rate, very little I tell you other than the very basics will help you fix this, so we'll stick to that.

After the car has cooled completely down. Remove the radiator cap. Is it full of coolant? If not, fill it. It should be full. Now look in the plastic overflow tank. Is it half full? If not, fill it half way. Using a less than full radiator will cause the problems you see.

Open your hood. Look down past the fan. Do you see the ground, or do you see a black plastic "floor" in the engine compartment? That plastic floor is commonly called a "belly pan". If it's gone, you'll need another one. You may want to ask whomever removed your old radiator if they removed it and forgot to put it back.

What brand of radiator did you have installed?

Lastly, the temperature needle should stay in the middle regardless as to the temperature. I regularly drove my Rx-7 in Phoenix when it was 110+ outside, the AC on MAX, and in both bumper to bumper and 80+MPH conditions. It never heated up.

 

It is filled up half way in the overflow tank. And the belly pan is down there, so that knocks out a couple things. i don't know the brand, i will check on that,

 

The problem is...THE STOCK ELECTRIC FAN ON THE FC SUX DONKEY *****.
The FC is the *ONLY* car that I know that will get hotter when the A/C is turned on.
Almost all others cars...the engine will get COOLER when the A/C is turned on, cause the electric fans turn on.

The stock electric fan is PUNY.
I bet if you put a bigger electric fan up there, this will NOT be a problem anymore...


-Ted

 

I've never noticed any change in coolant temps with the A/C on, and I don't even have the auxiliary fan any more (it died and has yet to be replaced).

The main fan is still doing most of the work, as the heat rejected from the condensor triggers the thermoclutch just like heat rejected from the radiator. The e-fan runs to boost condensor efficiency at low speed, not to keep coolant temps down.

 

Aftermarket water temp gauge?
Man, I surely did notice it.


-Ted

 

i am beginning to wonder if the steel rad. is up to the task too. Aluminum does sound like a better choice. I've had the car for a good couple years with no problems. The guy before who had it before me took good care of it. The old radiator was stock before i had it replaced. Its like it has a plastic top. kinda hard to describe. The part of the radiator where the "low coolent" sensor is, it wasn't steel, or aluminum, just plastic. Hard plastic, the kind that look like it could take years of wear and tear. Fun part is when the old radiator finally kicked the bucket. There was a 7 inch crack from where the plastic part ended on the radiator and the aluminum part of it began. My sensor went crazy, constantly buzzing me of low coolent, because it was literally gushing fluid faster then what i could put in.

Looks like i might have to dish out a couple hundred for an aluminum one, unless anyone can find one cheaper.

 

Yeah, the stock rad has plastic in it. You could prob go to a junk yard and find a rad in decent shape.

 

If the top broke just cary it AD shop. They will bend the tabs and put a new top on for you.

 

kinda late to get the old stock one back now. And i have been to a few junk yards, but no rx7 around. Alot of Grand Am's, but thats about it. I thought U Wrench It would have em..... nope. Oh well, i would rather pay out the pocket for higher quality. Just throw in the Aluminum rad., and sell the steel Rad on ebay or something. The rad is only a few weeks old.

 

Have you checked your hoses recently? The reason i ask, is i blew an upper radiator hose last week (before it broke, i noticed that it swelled when hot). After I replaced the hose, I noticed the level in the overflow tank actually rose when the engine was warmed up, like its supposed to. So my coolant system is under higher pressure now, maybe the low pressure was causing my overheating problems with the AC on. I have not tried running the AC in hot weather yet, so im not sure if it fixed it. But if youre having a similar problem, maybe one of your hoses is old and expanding when hot, lowering your coolant pressure, in turn lowering your cooling capacity?

 

That might be it too. I haven't replaced the hoses when i changed the radiator. Perhaps i should do that when get an aluminum radiator. Gota wait to get paid first. If i am going to change the rad, i might as well get the hoses done too.

 

The lower rad hose on a S4 with a Koyo needs a slight bit of triming to fit. Just so you know.