So I’ve been searching and scouring these forums for help but haven’t found what I’m looking for.

The issue: 1998 rx7 is overheating. And has something to do with the fans.

what I’ve done:
1) installed fluidyne radiator
2) installed pettit metal AST
3) replaced AST cap
3) installed cooler mishimoto thermostat
4) jumped TFA and GND to verify relays 2&4 are working along with fan motors and the fuse.
5) I have used a lisle funnel and burped the system multiple times to try and get the air out. I’m using 70/30 distilled water/coolant + a bottle of water wetter.

Here’s what’s happening:
when I drive the car on the freeway temps are stable. It’ll over heat idling or driving through town. Initially I figured this has something to do with the fans, and I was able to remedy the issue a bit by turning on the A/C.

I noticed on a few test drives that when I’d check the fans they weren’t running. My A/C switch is turning on the fans sometimes but not all the time. I thought this was due to a faulty alternator causing voltage issues, (I was having strange electrical symptoms like my DEFI gauges going dim) I replaced the alternator and started testing my fans. The first night, the fans would come on sometimes but not everytime, at one point the fans started acting strange and the speeds would vary up and down. I chalked this up to a dying battery and put the car on a tender over night and my battery is reading good voltage now.

I can hear my fan relays clicking. And when I jump TFA to GND the fan comes on. So I ruled out relays 2 and 4 the fuse and the fan motors. (The fans came on on every test I did this way)

I need to test the thermoswitch, but that still shouldn’t have anything to do with the fans not coming on from the A/C switch. The fans also do not come at the right temp, the car has seen up to 110c before turning it off and the fans didn’t come on.

I read my headlights can act as an extra fan input but the lights don’t turn on the fan or affect fan speed if they are on from my A/C switch.

im including pics of my grounds, and as you can see the bolts are pretty rusty and I’m pulling the bumper tomorrow to test continuity on them.

this issue has me pulling my hair out trying to figure out what to do.

does anyone have any ideas of what to check next or what this could potentially be?

massive thanks in advance for any help!

 

Are you running a power FC? If so you could at least check if the fan operational temps have been modified. You could always run a switch to manually to on and off the fans while you continue to troubleshoot if this is your only means of transportation.

 

im not. I purchased one but have yet to install it.

the car is pretty much stock aside from a cat back exhaust and high flow cat midpipe.

and I’ve got 4 other cars including a daily, the rx7 is just my garage queen lol so I’m okay taking time to find and fix the issue.

 

Before you get too deep into the electrical troubleshooting, one suggestion is to have a look under the front fender wells to see if your tires chewed thru the plastic fender liner and damaged any of the front wiring harness that lies beneath the liner. If your FD was ever lowered or is running on tire/wheel sizes other than stock spec, that kind of damage is a possibility and could result in a bunch of electrical gremlins. Since the fan wiring runs thru that harness, a quick visual inspection wouldn't hurt.

 

the car came with stock wheels and tires but that’s a good suggestion. I’ll check that today. Thank you!

 

Stock cars run REALLY hot. Read my fan thread, 110c on a stock car is not out of the ordinary.

But hopefully you can get those temps down.

Do you have the belly pan on the car?

Does the AC actually work on the car? If the AC doesn't work turning the AC on may not bump a fan speed.

Your car doesn't have the fan thermoswitch if it's a 98. 2 speeds are all controlled by the ECU. I don't know what temps the stock ECU kicks them on at on the later cars.

If you have a PFC and can get or borrow a Datalogit, spend the 30 minutes and install it. Since it's a JDM car you don't have to remove the 4 wires, it's full plug and play. Then you can drop fan speed 1 and 2 down to 85 deg. C or whatever you like.

Dale

 

yeah I read a bunch of your threads haha, super helpful.

belly pan is on the car and tightened up appropriately.

a/c works amazing.

I just learned about the thermoswitch after ordering the 85c one from Pettit lol. (Now I need to return it)

I have a PFC I got from crooober but I haven’t installed it yet and I don’t have access to datalogit, my hopes were the combo of the new rad+cooler thermostat would help keep it cooler.

I also checked the fan grounds in the picture.

1 is completely bad, the other only reads continuity on one part of the metal bracket, the rest is dead.

so right now my focus is fixing these grounds first and seeing if that makes the situation better.

 

-Update-

• i have done the RX-8 fan blade swap
• i have done the RX-8 fan motor swap
• still have the lower temp mishimoto thermostat
• still have the fluidyne radiator
• still have the aluminum Pettit AST
• 13psi AST cap
• I hooked up my PFC in case there was a weird issue with the way the stock ECU turned on the fans.
• My bottom tray is attached and is tight
• I have a vented hood
• Can’t find any leaks
• fan grounds redone and read continuity
• relays are all working when jumping tfa+gnd and tested new relays- fans still won’t come on on their own but work during testing
• 
  
  
  
  
  

after more testing here is where I’m at:

• My fans do not come on by themselves. (W stock ecu or PfC) The only way they turn on is if I press my A/C button. I got the car to 115C and the fans never kicked on. I am assuming they are coming on high when the button is pressed but I don’t know. When driving with the AC button pressed the car is fine until the outside temp reached 90F+ at that point any boost or elevation will cause the car to heat up, and then I have to turn on the heater + A/C button to cool down. However too much elevation even with the heater won’t cause the temps to stabilize.
• I can’t find any leaks, weep hole is dry on my water pump.
• i used a coolant funnel and checked for champagne bubbles. There are none- verified with a shop that based on the way the coolant looks, and the fact that I have no white smoke or sweet smells from the exhaust that my coolant seals should be fine.
  

Here are the potential solutions/questions I’m left with:

1) could it be a weird water pump issue? When changing my alternator I noticed the water pump bolt was super rusty. (Keep in mind weep hole is dry)

2) shop thinks it could be a bad water thermoswitch- however an earlier reply to this thread said it was the ECU that controlled my fans- and changing to the PFC did nothing

3) I’m reading my temps from my Defi gauge- could this be faulty or should be recalibrated?


what am I missing here?


Any help would be greatly appreciated. Closest rotary shop to me is 4 1/2 hours away, and I have to drive over 8k elevation to get there and that’s super sketchy with the overheating problem.

 

I'd say make sure your gauge is showing the correct temps. Check if it has a good ground.
Also lower the fans starting temp on PFC, and observe if it makes a difference or not.

 

I redid the grounds completely, they are all shiny and new and show continuity.

the fans do not come on in their own with the PFC or the stock ECU. I don’t have a data log it or pfc software so is that something I could even try? Do you have a resource you could maybe point me to on how to do this?

and yeah I dunno what to check for the defi gauges to be sure it’s showing the correct temp.

 

Yes, you'd need a datalogit, I missed the part that you mentioned you didn't have it.
Where does your gauge read the temps from? Temp gauges usually come with their own senders so they can show true/calibrated values.

Another thing I'd check is the continuity between ECU connector pin and the N2/N4 fan relays. This is to rule out any damage or short in the wiring.
You can even check the continuity between TFA pin and ecu connector pin. On USDM cars it's a Green/Black wire that connects to 3D pin on ECU.
On JDM models you need to do some digging to learn wire color etc. This might be helpful I guess: https://www.rx7club.com/power-fc-for...inouts-615909/