Ok recently my car starts to overheat after about 20min driving. It goes to about 3/4 of the way up the temp guage but no higher so far. One thing that puzzles me is that if I turn on the heater it will run at almost regular temp like 1/4-1/3 of the guage. I know that the heaer runs of the hot coolant from the engine and uses a fan to blow warm air into the car but can it really cool the car's temp that much or is it that by turning on the heater something else happens. I want to figure out what the hell is wrong I am not comfortable running the engine so warm. I have filled it with as much coolant as I can. Could it be the thermostat and how would I check that. I appreciate your help and thank you in advance.

 

Fill it with LESS coolant. Considering you're in Texas, it shouldnt dip to -20 like here (brr). If it constantly stays warm, then have more water. Not sure the exact numbers, but for texas in this time of year (what's your lowest temp?) run 50/50. In the summer when it gets really freaking hot run 85% water. Water is the best liquid thermal conductor. Almost twice as good as straight coolant.

 

I know its from our evil enemy cars site www.mkiv.com (i give credit to them) but here's the facts and numbers.

"5. why is such a low concentration of coolant recommended? i always thought that a 50/50 mix of coolant and water was the best protection for my cooling system.
maybe it's the best protection if you want to store or drive your supra (or 7 -Steel) safely at -40 degrees fahrenheit, but it's not the best mix to help your cooling system get rid of the engine's heat. first, understand that water is absolutely the best heat transfer fluid commonly available - bar none. all other heat transfer fluids can "carry" only fractions of the heat that pure water can. the effectiveness of a fluid's ability to "carry" heat is called its "specific heat capacity". for example pure water has a specific heat capacity of 1.0 and pure glycol (coolant) has a specific heat of 0.6. mix them in equal proportions (50/50 mix) and you have a fluid that will perform only about 80% as well as pure water in carrying heat away from the engine to the radiator. a 15/85 mix will perform 94% as well as pure water, or to put it another way, about 14% better than the 50/50 mix.
back to start
6. doh, i didn't sign up for a course in heat transfer. just tell me the right proportion of coolant and water to put in my system.
okay, here's just the facts: run the "least" amount of coolant you can in your system that will provide freeze and boil over protection "for your climate", throw in a bottle of Redline water wetter too, and fill the system the rest of the way with "pure distilled" water. here's a table that's pretty accurate so you can pick which proportion will work best for your climate. all figures are in degrees fahrenheit.

% Coolant Freeze Boil

20% 16 253
33% 0 256
50% -34 265
70% -90 277 "

edit - along with that, check your thermostat.. Aw hell, replace it with the mazda oem one, and make sure your radiator isnt blocked. But if you're running a shitload of coolant and not much water, then that could be the root of the problem.

 

Does your car start cooling down while driving, and heat up while idling? That could indicate a failing fan clutch.

 

Make certain that you always use distilled water in your coolant mix, or you'll rot your cooling sys from the inside out.

Find and use Redline Water Wetter. Excellent stuff.

http://www.redlineoil.com/products.htm

Click cooling products, then 'Water Wetter' at the start of the first paragraph for lotsa 411. I used two full bottles in my last coolant change and she's running as cool as she ever did (never gets over 1/4.)

When was the last time you stuck your head under the front of your 7 and looked at the front of the rad (and oil cooler, too?) Who knows what roadkill might have been scooped up in there and is now reducing airflow...

My own trick for cleaning the rad is to remove it from the car and spray the hell out of it (just the fins!) with aluminum rim cleaner (rim as in the big round thing your tire goes on) and then let it sit for 20-30 minutes. Then spray it out with a garden hose. It's great for getting out dirt build-up. I don't recommend using compressed air on a rad - I tried it once and all I did was bend fins.

A new thermostat is a good idea. Make sure you get one from Mazda - aftermarket units are widely reputed to be garbage.

 

Well the lowest temp recently was 31F and I think since I added some premixed prestone50/50 mix but then Ithink it had like a 60/40 mix before and the stuff I topped it off with recently was 100% cooliant.

How hard is it to replace the thermostat?

My car (right now) will actually cooldown alittle while cruising at 50mph but turning on the heater also cool it to norm temp as long as it is on but then if you turn it off it heats back up. I guess I will flush the rad. and see if that helps and run a higher water content I guess I will try 30/70 .

TO remove the fan clutch do I just remove the bolts on the pully and pull it off or do I have it wrong? I have a spare used clutch from the gxl I just bought and could swap it to see if it is that. I don thinkso though because it will still overheat at low speeds like 30mph.

Could having a 1200rpm idle make this happen? or running rich or lean?

 

You'll always run cooler on the highway (unless something is seriously messed up.) All that airflow with relatively lower revs. My '86 NA hits 182F while city driving (then the e-fan kicks in) and drops to as low as 160F once I get out of town and get cruising.

As for checking the clutch, hang on...

Here: https://www.rx7club.com/forum/showth...ght=fan+clutch

Your 7's idling at 1200? It should be at about 750. When was the last time your TPS was adjusted?

 

never do not have multimeter I am pretty sure it is messed up now.

 

zthanks for the link preciate it.

 

actualy sometimes it is at 1200 but then when it is running a bit warm it idles at about 780rpm at the stoplights. I dunno but my acv is also fu@#ed up so I dont know what is really up but I am trying to figure it out.

 

Not done with you yet!

http://fc3s-pro.com/TECH/HOWTO/TPS/tps.html

And bookmark this site: http://home.rmci.net/panther/tech.htm

 

cool thanks but will it be the same thing for my N/A s4?

 

Here's one for the NA!

http://www.johnr.com/tps.html

 

Looked at the thread again.

Idle drops at stop lights? Meaning it drops when you have the brake on? That circuit draws a fair bit of current (it does on my 7.) The BAC is supposed to kick the engine speed up when there's a heavy electrical load. Maybe your BAC is bad and that's fudging the rest of your set-up...

 

Sounds like you got the same problem as me. I just asked a few people what my car's problem was. I talked to a guy out here in the Bay Area who is the Rx7 guru--everyone has delt with him at least once. He told me something pretty depressing. He said its a leak in the water jacket into the combustion chamber. Said that once they overheat--its all bad. Half the engine is Aluminum and some parts are iron and when they overheat, they become different dimensions. So guess what he said to do: NEW ENGINE. I'm just gonna run it to the ground. His prophecy may be true though, I just replaced the coolent with fresh, and Its already looking dirty....

 

Woah! Woah! Woah!

Overheating does not instantly equal cooked water jackets! There are several things to be checked first. I'm sure that the guy you talked to knows his stuff if he comes so well recommended, but telling 1987RX7guy that his motor is stewed based on the little info that he's given us is not doing him any favours.

A quick and easy test to see if your water jackets have failed is, with the engine both off and cold, take off the rad cap and then start the car. If coolant spews out (not farts, SPEWS!) then the jackets are fucked. If it doesn't, the cause of your problem probably lies elsewhere (pulling the cap is far from scientific, so rather than saying that the jackets are 100% I prefer to say that they officially become the least-likely culprit.)

Don't throw your motor away yet!

 

I love it when someone brings sanity back into a thread. Thank you!

 

I am pretty sure my engine is not fudged up dude. Reason is because my engine has never gone past the temp it is running at right now and never will as long as I drive it. I will do that test tommorow and get back to you guys but I seriosly doubt it. Besides doesn't your motor's exhaust come out with a lot of smoke and such. My car has only smoked twice on start-up 1.Replaced pulsation damper 2. the one time my car got flooded and never on anyother occasion.

and yadaman
Exhaust Leak means something I did not give advice to other people until I had more than 5 posts dude (way more)

"A wise man learns in silence"

 

oh amur my car returns to normal temperature when I turn on the heater. You would not happen to know if this is a problem with the heater core or somthin.

My car (at stop light usually idles where it is supposed to but I usually do not use the brakes I just hold the car with the clutch or nothing at all. Life up there in canada is different so are the roads I live in texas(dessert country dude) flat *** roads.

 

The exhaust can spew a lot of white 'smoke.' The way to diagnose it is simple - smell the cloud. Burning coolant is very distinctive and a scent to fear.

When bought my first 7 3 years ago, the motor had a cooked water jacket. But I didn't know anything about rotaries and the guy I was buying it from was a crook. The exhaust dumped tonnes of white smoke on start-up, but I didn't understand what it meant. The motor died 2 weeks later.
I found a replacement engine in a matter of days. I'm still running on it in my 2nd 7 (first one was greased in a collision that was not my fault.) I've had temp issue with it that I managed to finally resolve this past summer.

So, my point is that I've already been through the water-jacket nightmare and I'm not just talking through my hat.

I still remember when I took the car, just after I'd bought it, to a shop and this kid yanks the rad cap while the motor was running. GOOSH! He ducked and ran pretty fast.

Have you given the sys a once-over yet? Looked for blockages? Checked the fan clutch yet? Come on, young man - I don't have all day.

 

I'm sorry, but I can't stand this anymore....Complete lack of logic and proper troubleshooting.

Please see http://www.aaroncake.net/rx-7/cooling.htm before going any further.

 

I am at school and posting this stuff durring the breaks in between. I am going to buy some more soolant so I can do the flush and will test the fan clutch when I get home it should be warm by then if it is that I have a spare one to swap in the belts look pretty new maybe a year with them on the air pump is still not off so both are pulling the water pump.
Aaron cake-c'mon man I am still kinda new to this stuff I just wanted your help you don need to be a dick all the time dude. I read your site and it was helpful so thanks for the link man even though you're kinda harsh sometimes I appreciate it.
Amur--I will get back to you all tommorow after the radiator flush.

Anyone know why my car would cool down when the heater is on? It lowers the temp half of the guage that is a lot to me. Do we just have good heater fans or what?

 

I don't quite know what to make of that...



Have you thought about putting an electric rad fan in?

https://www.rx7club.com/forum/showth...ight=fiero+fan

The Fiero fan makes a reliable, cheap choice. The Flex-a-lite that Aaron recommends on his site is a great product, but it is loud as all hell. I have a Fiero fan in my 7 combined with a Flex-a-lite temp switch. I set it to spin the fan at 182F and forgot about it. It works perfectly.

 

It is ok I was just wondering.

Ok update I just drove home and the fan is in pretty good condition I spun it with my hand and it only goes about 3/4 of a turn no metter how hard I try to make it go further my car was only at the 1/2 mark but it is like 45-50 degreez out hear and that might have helped the cooling but I am going to go to auto zone for the coolant and fluch thing. Is it okay to use that stuff (flush thing by prestone) or will it mess somthin up. Where is the walve to drain the cooliant from the radiator. I know it is like a screw but can you all help me get the specific location of that thing. I am not going to do the flush now since I have to go pick up my g/f at her job and go to a meeting at school for a computer club I am in so I don want to be flushing in a hurry or in the dark.

I notice something wierd though when I was driving home I heard a buzzer type thing when I would:
1 turn right
2 accelerate heavily
3 go over rough pavement

it is not the overrev buzzer cuz I was driving normally(not my normal just like a sane person) what could it be?

 

I don't know. I've never really had to deal with the stock fan - I got rid of mine b4 anything went wrong with it.

Quote:

auto zone for the coolant and fluch thing. Is it okay to use that stuff (flush thing by prestone) or will it mess somthin up.

Nothing wrong with the Prestone flush. But leaving it in for only 10 minutes like the instructions say is a joke. Put it in (bleeding the rad when you do) and take the car for a 20 minute spin. You don't have to pound on it when you do - you just want to circulate the flush as much as possible.

Now for some controversy. Below is a thread that A) was highjacked and B) got a lot of people very angry. Starting at the 11th post is a discussion/debate/rampage about an alternative method for doing a coolant flush on an RX-7. Check it out and decide for yourself...

https://www.rx7club.com/forum/showth...light=aluminum



Dead center on the underside of the rad. Btw, are you using an aluminum or a copper rad? If you don't know you might want to find out - my 7 mechanic says that the copper ones are garbage.


Buzzing or beeping? If buzzing, it may be the coolant warning buzzer. If your sys is otherwise full, you probably have an air bubble. Since you're about to flush the system, I'd say don't worry about it. Just make certain that you bleed the rad when you refill everything. Also, Aaron (Captain Tact above ) has mentioned that he disconnects the hose that goes from the engine to the heater core on the driver's side of the engine bay. He disconnects the hose at the heater core pipe. This gives air a 2nd escape route.