Cooling fan/cooling issue
 

Okay I'm in the middle of troubleshooting my cooling system.

First with the cooling system itself, I just replaced thermostat because old one was being slow. We're in the process of burping it and car was getting too hot so we shut it off. Upper radiator hose is hot, lower one not so much. Car only ran for 4 mins or so. Thinking clogged radiator? Idk.

Big reason the car getting hot is my fans. They won't activate. I checked fuse and relays and all are good. Fans turn on when A/C is switched on but looks like not reacting to thermoswitch or ecu temp sensor.

I just had my harness redone so maybe they messed up on wiring, but I can't imagine them messing up on both sensors.

Im running a 16 psi pressure cap, a upgraded radiator(not sure what brand came with car), stock everything, other than catback.

Running water wetter and full distilled water.

Body Electric Troubleshooting manual (in stickies) has a diagnostic procedure.

I looked in there can't find anything about it. I already did tests from the FSM which was the relays and the fan motors themselves.

Burp the system wthout running the engine. Do you have a temp gauge? If so how hot is "getting too hot"? The OEM thermosensor won't trigger the fans until 105 C.

I shut it off at 220 230 F. The air in system may be throwing it off too because I T'd the throttle body coolant line. We fill up coolant then run engine to try to get water circulating.

We been squeezing lower hose to get air out with engine off. I have a FC thermoswitch in there

Sounds like your fan is not turning on.

I would personally try and activate the fan manually by supplying power and ground to it to MAKE sure the fan is not toasted itself. Then if it does, the problem is within either the harness itself, faulty sensor or faulty ECU.

Did you turn your HEAT on HIGH and fan on LOW while trying to burp the system? It will get the coolant to start circulating by turning the HEAT on HIGH.

I hope this helps.

-AzEKnightz

Haha Eric I was about to call you for your opinion too lol. We supplied power to fans and ones working great, other is kind of getting tired but still runs. The fans come on when a/c switch is on so their not toast. A cel recently went up so I have to check that, I'm pretty sure it's cuz of a missing egr solenoid, but can possibly be ecu coolant sensor.

I see, that's good.

I personally DONT see the ECU being the culprit, its either the harness OR the fan switch itself.

I'll check continuity from the fan switch side to the ECU pin side to make sure you are getting a good continuity. If so, then your problem is your fan switch. Make sense?

-Eric

Are you talking about the fan thermoswitch to the ecu pin? It shouldnt be the thermoswitch because I just bought a FC one from Ray. Yeah that didnt make too much sense.

So you are using a new FC switch. Then most likely your problem lays within the harness from the switch to the ECU.

-Eric

If my harness is messed up to the thermoswitch wouldn't the 108 degree ecu switch above the thermoswitch activate the fans?

Personally I fill, replace cap, squeeze hose, remove cap and repeat.
As far as checking fans...... Cooling Fan Test Proecdure and FAQ

Wow that cooling fan test wasn't in factory manual. I'll try those in a day or so. Question though, I took out my fan recall harness that connects to ecu. Since I don't want fans on after driving that's all I needed to remove?

after a flush, i drive it easy until it cycles a couple times. usually takes care of the air in the system.

if you aren't able to do that, its most likely the fans or radiator.

do you get different results at speed? versus traffic? or same issue all the time?

fyi, heater switch moves a blend door, not a valve. having the heat on will just make you very uncomfortable.

haven't done any driving yet, never mentioned anything about the heater.

I only had time for one test, I grounded the TFA connector and the fans came on at low speed, and according to that guide its not ECU or the switch. still have to test medium and high.

Thank you for the pointing this out, I totally forgotten that I am dealing with a FD here. Was thinking of a modern vehicle that uses water valves that flows coolant...


I also do not know about this Fan Testing method. Great info here.

-AzEKnightz

The thermoswitch and ECU temp sensor are in fairly high points in the system. Could it be that the coolant level in the system wasn't sufficient for them to get a good temperature reading and request the fans?

Can be possible, we are burping system so maybe theres too much air to reach the sensors? My aftermarket gauge on the TB coolant line is getting a reading though.

Based on my cooling symptoms do you think I need a new waterpump? I might do fan switch mod to get fans on.

Coming to conclusion that coolant seals are bad.

Are you SURE that both fans are working correctly?

We had one bad fan motor and it caused us all sorts of problems including not just overheating and it's coolant issues BUT an a/c that did not cool properly. We replaced the bad fan an What a difference, car ran cooler plus a/c worked better.

I have one fan that is kind of getting slow but still running with the other fan. I'm going to see if Mazda sells fan motors by itself. Don't really matter now though. Coolant seals are bad.