sdrx8

I have a 2004 RX8 that has never had any cooling problems. I just replaced the overflow reservoir to get rid of the dashboard light and of course the brittle 8 year old plastic nib broke off the radiator, so I had to replace that too.

Drove it 4 or 5 times to work over a couple of weeks and everything seemed fine. Took my daughter through a fast-food line where they made us sit about 8 minutes for our food, and it over heated. I never saw a dashboard light and it was pegged. Cooled it off and topped off with water and it started and drove fine.

Apparently the fans are not working, so if left at idle I will eventually overheat (pretty quickly once it gets to the right temp). I idled it in the driveway today and the fans never came on.

What is the fan circuit like and is there a proper way to test and diagnose the fans without overheating as the test?

1.3_LittersOfFurry

iTrader: (4)

I'll post up the schematics for the fans tonight when I get off.
Only help I give right now is;
There are 3 relays and a fuse under the hood, might wanna check them out.

1.3_LittersOfFurry

iTrader: (4)

Oh, and the fans should come on around 210-213*f and turn back off around 200-203*f.

Socket7

The RX-8 uses coolant without water. If you are sticking to stock fluids, you're going to have to flush your coolant and replace it.

If you mix water with OEM RX-8 coolant, you're gonna have a bad time.

Not sure why your fans aren't coming on, but the topping off thing stuck out to me as something important you may not know.

9krpmrx8

iTrader: (46)

Fl22 is premixed, adding water just dillutes it but it shouldn't cause any major issues since distilled water works better at cooling anyway.

OP, if you need the fans replaced I have the factory set from my old setup, I'll sell it cheap. They are old but work.

Socket7

Corrosion is a major issue.

It just doesn't happen instantly.

We have no idea how Soft or hard the water he put in his radiator was, we have no idea if it was acidic or basic. We don't even know how much. I can tell you though, they don't sell distilled water at McDees, so he probably didn't use distilled (which would be the kind of water least likely to corrode your cooling system).

Having a higher boiling point on my coolant is more important to me then a slight increase in thermal transfer rates. Steam doesn't make a good coolant at all. (not that an 8 should ever run hot enough to boil distilled water if it's working right)

laythor

Hey Socket7, long time no see!

sdrx8

The water is pretty hard in San Diego.

It was filled with distilled water and a generic ethylene glycol coolant before the emergency top-off. I can flush it once I get it straightened out.

I'll check the fuse tonight. I can check the relays to see if they are connected, but I am not sure how to test them other than that.

Is there some sort of test mode where I can make the fans turn on without the engine heating? I don't want to keep heating the engine to test the relays, since it heats up really fast at a certain point.

04Green

iTrader: (1)

See step 13 of the $100 thread in my signature. It points to how I turned the fans on low. You can, I believe, do the same mod to the high speed relay to switch that one on.

Also, if you replaced the radiator, make sure you burped the system. You may only be half full of water. disconnect the hose that comes out of the top of the throttle body and fill the radiator again.

Socket7

Nice to see someone remembers me!


SD, yeah. I don't think your coolant mix is anything that needs to be taken care of right away (before fixing the fans). Just wanted to make sure you knew you don't dilute FL22.

nycgps

iTrader: (1)

dude ... RX-8 uses regular coolant u see on the shelf ... oh fine even the FL22 bs is just 55/45 mix ...

you CAN MIX H2O ... it just water the EG count down ... it will NOT effect the cooling, as long as it's Distilled.

As for Corrosion protection, you lose them even u never add water to it. Even running on pure Water will not melt your engine/car right away ... it takes time for rust to form. I wouldn't run pure water because the Water pump seal will fail, that's what EG/antifreeze is for.

and where have u been Socket7 ? forgot to say hi.

nycgps

iTrader: (1)

Pure Coolant (100% EG) has massive amounts of anti-corrosion additives in it. You can mix it with tap water, it's not good, but it will not kill your system over night.

Just drain it all out using the Engine drain plug. and refill and bleed the system again, good as new.

Socket7

I've been dealing with the slings and arrows of outrageous fortune NYC.

I've only just started getting time again to properly pamper my car. You don't even want to KNOW the last time I washed it...

1.3_LittersOfFurry

iTrader: (4)

Hope these help.

sdrx8

Those help a lot. Thanks.

sdrx8

Thanks again for the schematics.

It was the 40A fuse, but of course it wasn't that simple.

The first time I looked, I only saw the small fan fuse and completely missed the big fuse. That turned out to be a good thing.

This weekend I finally had time to unbolt and pull up the air box so that I could get access to the fan. That is when I found the rat caught in the fan blade and draped across the fan connector. I'm not sure if the stuck fan caused the fuse to pop or if the rat shorted the connector, but I'm glad I didn't replace the fuse before I found and removed the rat.

Thanks again for the help.

Alean

Hey guys,

My car overheats only when I have AC on. I came to a conclusion that when I turn my Ac the Fan should kick in and it actually does and the car runs smooth then I see it going the mid line and car starts blowing warm air and feeling weird and I checked the fans and its off then on all the time. It makes a clicking noise when it turns off. Is it the relays that making malfunction and thats why it overheats only with ac on? Help

Nisaja

Your AC is cooled by the AC condenser. The condenser is placed right in front of the radiator. When the AC is on, the condenser puts out a lot of heat. This heat directly hits the radiator, and that means higher coolant temps. It could be just too much for the fans to keep the coolant temps in check. That is the theory behind "only overheats with AC on".

The AC blows hot air because the AC turns on and off every 10 seconds when the car is overheating, to reduce the amount of heat the condenser puts out. That's probably the clicking noise you hear.

The solution, however, is a lot less simple. This happens when the cooling system is weak. Meaning there is something wrong somewhere.
What are your ambient temps?
Does this only happen while idling? Then you need to test if both fans are working properly. What year is the car? These fans are know to slow down overtime. Electric fans don't just stop spinning. They slow down gradually. So even if they're pretty loud and spinning fast, they might not be spinning fast enough.

Are there any leaks in the system? You might want to pressure test the cooling system. Any small radiator shop should be able to do it.

Report back with your findings and we'll guide you from there

Alean

Thank you for the reply 😀
My rex is 2004 with 82k miles. The ambient temperature is 102-106 F so it's pretty hot outside. The car drives smooth fro like 10 minutes with AC on when the weather is that hot then the symptoms start and fan starts kicking on and off every 10 seconds then i turn off completely AC and the line goes back to the middle. That only happens when weather is 102 which is every day. At night it overheats but takes longer tho. I don't see any leaks. I would love to take it to a garage but I'm really low on momey 🙄

Alean

Some dude at Autzone told me it could be the relay that need to be checked because a relay makes a clicking noise and turns off and on but I don't know

Alean

Another thing to point out , I was driving the rex all morning like 9-11 am and the AC was really cold and car wasnt even overheating. I started using it rigtnow again like at 1 pm which the sun and heat are at its best and car started climbing up 3 lines from middle line so I turned off the ac and went down to mid again and didn't overheat until i rev it really hard. I was trying to pass some old grandpa and line went up 3 lines again then went down again. So weird

Nisaja

Does the car only overheat when you're idling? Or does it overheat when you're moving fast too? Say you're moving at 60mph for 5 mins, does it overheat?

Get the fans checked. They shouldn't be cycling on and off like that. At that coolant temp, they should be running continuously at full speed. The AC compressor might click on and off because the ac turns itself off every 10 seconds to reduce the heat coming out of the condenser.
Replace the fan relays. See if that fixes it. Are BOTH fans spinning?

Next time it overheats, turn off the AC and turn the heater on full blast. The heater acts as a secondary radiator. It'll pull in the heat from the coolant into the cabin. Sure you'll sweat, but it'll save the engine. Keep in mind that this can only save you from a minor overheat. If somethings seriously wrong in your car, it's not gonna stop you from overheating. But it should HELP. Don't let it overheat often. You might lose the engine! In fact I wouldn't even drive it until I get it fixed.

Are you sure you're not losing coolant? Is the coolant level holding steady at the Full mark on the coolant reservoir?

Is your radiator blocked by anything? Crawl under there and see if air can freely hit the radiator.

Alean

Yes the car overheats when I rev the car. Lets say there is someone really slow in fron of me and i pass them and rev it it goes up even sometimes at 60 mph but it goes up like 4 lines but it never reaches the red light. But it overheats usually when ac is on the. I turn it off then goes back to mid line. How would i know if the relays are bad? And what relays should i check? Colling1 & cooling2? I want to fix it but im really shor on money and plus usually no ones knows how to work in this cars.

StealthTL

iTrader: (1)

If you pull the two cooling relays, you will see the two large contacts that do the actual switching.
Using a stout piece of wire, jumper these two and a fan should turn.
If it does, the relay needs replacing, if not, the fan motor or ground is at fault.

The rubber stoppers that hold the airbox in place sometimes get pushed down into the fan blades - this jams and burns out the fan motor.
Been there, T-shirt acquired.


.

Nisaja

Oh yeah! Those stupid grommets fall through the air box tray and jam the fan. If you've pulled your air box recently, and this only started happening after that, this just might be it!!