Hey guys.. and gals.. question for you

I've searched and searched.. so the issue I'm having is in an 08 tC. I had a problem with it over heating. The over heating would start when I'd drive somewhere and then let it idle. After reading some suggestions on here I changed the thermostat and did a complete radiator flush. Then that didn't help so more threads on here suggested making sure the fans were turning. They weren't so now I know that's my issue. I can turn the fans on with the ac and they both spin and that immediately cools it down to normal temp. But its like a pulsing so they turn on and then eventually turn off and back and forth. Ive swapped relays and checked both fuse blocks and they didn't help. I've also changed the coolant temp sensor.

I'd really appreciate any suggestions. I've got countless hours researching this so I'm pretty desperate. And its so frustrating when people fix their problems and don't come back to update and tell others. Scouts honor I will post and give updates.
Thanks good people.

 

Not sure if this helps, but here is the diagnostic procedure from the service manual.

 

I'll definitaly give it a shot thanks! I appreciate the response either way

 

Update please

 

My update is that I still don't have it figured out. The link is helpful in ruling out some things. I threw a code while I was working on it. I believe I did it as I was troubleshooting but I'm not certain. I'm going to have it scanned to know. I just don't understand how the fans turn on with the ac but not when it heats up.
The link ruled out the fans and the coolant temp sensor.

There may be a break in a wire that I can't find. Or it could be the ecm. The link suggests the ecm but without buying another to swap I don't know how to rule that out.
I will get back here after I have it scanned. My wife just drives with the ac or heat on to keep it from over heating.
Thanks everyone

 

Not sure if you have a scan tool, but you can also check for the reported engine coolant temperature through the OBD2 interface. When the car is fully warm (maybe even a little hot to the point that the fan should really be on), check the reported coolant temperature. It should be above 96C (205F). If it's reading lower, then there is an issue with either your coolant temp sensor, the wiring to the ECU, or the ECU itself.

Generally if there is an issue with the wiring, the ECU should detect this and give you a code, so I wouldn't think this would be the case. Still, you need to rule things out. If the reported temperature is above 205F and the fans are not on, then there is a problem with the signal that should be telling the fan to turn on, not the incoming signal from the sensor.

 

you need to stop driving the tC until you figure this out. Why? because the 08 had the old designed water pump. Toyota has since updated it. If the water pump goes bad then of course the engine will overheat. But in the tC's engine it allows the inadequate head bolt design to begin to pop the head off the block. Usually if the water pump is working fine this doesn't happen. When the overheat begins then oil consumption will increase.

Check the drive belt area, look down in between the belt's routing and look for what would be a "salty" residue. That's a sure sign the water pump is leaking via it's weep hole.

I doubt it's your cooling fans, as they do come on, it's the water pump that needs to be replaced. And definitely get the Toyota brand one, it's the redesigned part, who knows which version aftermarket is using.

 

I appreciate the help. I've borrowed a friend's scan tool but it's pretty basic so I doubt it does the temp. I'm fairly certain it is over heating because one time it actually boiled over out of the reservoir tank and steam came out from under the hood.

I understand what your saying about the problem with the car telling the fans to turn on because if I read it and it says over 205. Then obviously the car should know that. Thank you. I didn't think of that. So maybe I can look for the ecm wire diagram to see what wires output for the fans to see if it's outputting the 12v and go from there. Thanks again. I do appreciate

 

Thanks for the help. But I'm fairly certain it is a problem with the fans. Because the temp will be climbing and in the red, I jumped out and the fans weren't on so I turned the ac on and as soon as the fans kick on they temp drops pretty dramatically. But once again thank you

 

I was thinking this same thing. I did a quick look yesterday, but all I was able to find was the sensor's input circuit into the ECM. Didn't see the fan signal output. That's not to say there isn't one, but I wasn't able to easily find it. That is what I was suspecting, however.

BTW, if you or your friend has a bluetooth based OBD2 scanner, you can purchase the Torque Pro app on your phone for 5 dollars. It can monitor a plethora of sensors, including coolant temp.

 

I forgot what you had determined from the diagnostic procedure. When you unplugged the coolant temp sensor with the engine running, did the fans turn on, even while cold? It's supposed to. High resistance tells the ECU that the temp is high. Unplugging it should tell the car that you are overheating and it should in turn run the fans.

 

I did unplug the sensor and the engine went to a high idle and then dipped. Giving me the 2 check engine codes. So I know the sensor works. But the fans never came on.

 

Also if anyone has the wire diagram for the ecm I'd really appreciate it. I can't find it online but it would be nice to test the wire coming out of that to see if it's trying to turn the fans on. Then I'll know if it's a break in the wire or not

 

One last thing, with the AC on, do both fans come on or just one?

BTW, I'll see if I can get a wiring diagram. I looked for this earlier in the week, but I didn't see an fan output trigger listed.

 

Hmm, so I looked through everything related to the ECU pinouts, and there is nothing that even alludes to a fan output. Unfortunately the service manual is light in this area.

If you look again at the diagnostic procedure in the link above ("onvein40"), it says to check for a short in the connection between the cooling fan relay and the temp sensor. This suggests that the sensor is also routed directly to the relay (seems odd, but that's what it implies). It doesn't say which of the two relays (or both maybe?), so you may want to trace the wiring from the sensor to the relay box. That may be your best bet at finding a short.

Before doing all of that though, do a full diagnostic check on both fan relays. I wouldn't trust just swapping relays as a means of ruling them out, especially since one of them is a 4 pin and the other is a 5 pin. Follow the diagnostic procedure in the other zipped file ("i740001")

 

Thanks for checking! Both fans come on

 

There is 3 relays. 2 are the exact same so I swapped those. But I will check into the wiring to see if I have a short in the wire. Thank you

 

Ever find a solution to this problem? Having the same or similar with my 05.