Coolant Problem on a 1993 RX-7.

Lately the coolant needle has started to rise towards hot while the car is at a traffic light or stopped with the engine still running.

While doing highway driving the needle stays constant in the middle.

I have checked for coolant leaks and there are none.

I also checked the silver coolant tank and there is plenty of coolant.

Would appreciate solution / assistance from the Group please.

Thank You.

 

Have you confirmed that your radiator fans are working properly?

 

Temp information from an additional manometer?

Just to know how hot your car become......stock gauge for me is a little shitty

 

"Have you confirmed that your radiator fans are working properly? "

Thanks for the quick reply.

That's the first thing I thought of that it could be the Radiator Fans not coming on.

I did'nt mention that in the initial post as I wanted to hear all the solutions.

My question - Is there a relay or a fuse that makes the radiator fans operate?

 

^ There are 4 relays that make the fans operate.

 

The fans should automatically come on at set temperatures (I don't remember what temp off the top of my head), you can also prompt the fans to come on by turning on your A/C.

 

"The fans should automatically come on at set temperatures (I don't remember what temp off the top of my head), you can also prompt the fans to come on by turning on your A/C. "

I'm not exactly sure where I can change these settings. (For the Fans to come on at a Certain Temperature)

I'm thinking somewhere at the thermostat?

I know that the PCM detects coolant temperature and turns on the radiator fan. But I dont know where I can do this.

 

1st just be sure your fans are coming on my guess is if they are they are on low speed once you solve that you'll likely fix the problem? Quick test is simply push the AC on button and see if the fans turn on. I have some relays and fan assemblies if you need to replace them.

The stock fan thermo sensor is around 190 but you can replace it with an FC sensor and the fans should come on around 175. If your car is healthy you should have no problem managing temps as high as 220 with properly working fans so no reason to get the FC switch IMO unless you drive in stop and go traffic frequently.

If your sensor is moving you have a serious problem and need to fix it fast before damage is done to the motor. The FD gauge may as well be a red light because when it starts to move the temps are already around 220 or 225 which is too hot because just going 20f highter to 245 can and will cause engine damage.

Forget worrying about the thermo sensor or a gauge and buy a PFC and solve both problems along with tons of others. You can set the fans to come on early with a PFC, it has an accurate water temp gauge, you can set a higher flow oil injection, immediately get better gas mileage etc....etc.... all things that are beneficial to your cars overall health with many many other positive features for the low price of 750 (used). Lots of talk recently on this forum about the benefits of a stock ECU...........WHATEVER.............a PFC will win the ECU debate hands down every time.

 

Fritz - Thanks or that valuable piece of information. I'm going to try (Make Sure the Fans come on when I turn on the AC) this evening and get back to you. For now - Let me just ask you this. If the fans are set to come on at low speed where do I change the setting for them to come on at a higher or different temp. You may have answered it in your initial post but I'm sorry if I'm asking again.

fendamonky and RENESISFD - Many thanks for your feedback aswell.

 

In stock form, here's how the fans are controlled:

https://www.rx7club.com/3rd-generati...3/#post9747053

 

You cant , Unless you get a PFC . The FC thermoswitch will just turn them on a bit earlier .

 

Just looking at this tells me 1st my #s are way off OOPS and second if the needle moves you are asking for serious trouble.

I just recalled memories from my early track days and seeing 110c (220s) all the time and the needle probably doesn't move until around 117c or 240 plus F so your car is getting seriously HOT!!!!!

 

Have you check the thermostat? I had the same issue when I first got my car couple years back, needle will move a little past the middle point at red light and the fan will kick it back down, turned out I have a sticky thermostat.

 

There's been a lot of great recommendations since I've posted my inquiry. I have'nt had the opportunity to work on the car today. Thank You and I'll post my findings.

Please continue to offer more suggestions.

 

Thermostat is extremely simple and cheap to replace. I'm with everyone else, gauge shouldn't budge above 1/2. You are running the factory coolant system? Nothing is deleted or routed differently? Low coolant buzzer hasn't went off, smoke on start up?

 

"Thermostat is extremely simple and cheap to replace." Yes, I've done this before a while back and I just need some time away from work to do this again.


"I'm with everyone else, gauge shouldn't budge above 1/2. You are running the factory coolant system?" Yes, I am.

"Nothing is deleted or routed differently? Low coolant buzzer hasn't went off, smoke on start up?" Low Coolant buzzer has not gone off and no smoke on start up. As a matter of fact, I drove it this past Sunday and the needle stayed right in the middle. No coolant on the ground and no leaks anywhere.

It's possible that the needle did not rise towards hot because the engine did not get to run for an extended period of time while I was not driving. And letting the engine run at an idle speed.

As Fritz has mentioned above - I am going to make sure the fans are working properly by turning the A/C on.

 

If the thermostat wasn't opening it would get hot even when cruising so that's probably not it.

 

MX3 - Man it would really help for you to fill these folks in on what your setup is. For one, aren't you running a 3.8L fbody V6 swap? I'd hate for you to waste these peoples time troubleshooting rotary accessories when that's not even what you've got up front... For instance, I seriously doubt you're running the stock thermo switch. Then again, it's hard to know since nobody except possibly you and the original builder of the car (Pez if I remember correctly) knows exactly how your fans are controlled. Without more info about your car we're just guessing in the dark.

Just my 2 cents.

Lane

 

Fritz: Wouldn't higher water pressure at cruising RPM help open a slightly sticky t-stat?

 

Yeah, if it's a Ford we're talking about then I understand why you have no PFC. If there's a Wankel under your hood, even a base-mapped PFC will awaken your car. When I ditched the Pettit ECU and put in the PFC, my car instantly ran cooler and smoother, got better mileage, quit hesitating at 4500r's, etc.
Once Kan tuned it...it doesn't even feel like the same car. Money well spent.

 

^ Huh?

 

Just FYI, he does have two FD's:

https://www.rx7club.com/3rd-generati.../#post11465479

So while one may be a V6, the other may not.

 

You could have air in the system and would need to burp from the throttle body which is the highest point but I would change the the sensor (with FC version), thermostat and waterpump. That is so much cheaper then a new eingine! The engine is just way too sensitive to overheating to not consider the small cost in comparison. They all can be replaced on a sat in your garage. The only issue you would have is coolant spill and disposal.

 

Good point it may not be opening all the way or sticking etc......

Hopefully the OP would mention if we were discussing a v6

 

He's got the same thread going on norotors.com

Lane