Radiator Fan wont turn on automatically w/ new 170 thermostat

[AFG-DSM2g]

First Background: I have a Auto 95 GSX, 70k original miles, 11k on one of the last oem factory built 99 gsx motor. Current engine regarding mods: good quality ebay intake, good quality jdm sport fmic, Full 3" Exhaust, simple bolt on mods. Still on stock garrett t25, pushing stock boost

So my issue is that my car is having issues cooling down. I had to do emissions so i took off my full 3" exhaust to put my oem exhaust back on. I had issues passing so i was rocking the stock exhaust for about a month. As soon as i changed it, i noticed the temp guage was getting higher. (I have all oem guages). I thought this was just because this exhaust was back on. I changed both my o2 sensors and passed emissions then put my full 3" exhaust back on, hoping the temp gauge would read normal again. It didn't. It felt like it would only get really bad when id drive uphills, or when my turbo would spool up a lot. I decided to change my radiator fluid. I didnt do a full flush, just drained then re-filled with Prestone green. I burped the system too. I also decided to change the thermostat to a 170 degree one. After I did all that, the car started FEELING hotter, to touch. Like when i'd touch the valve cover or radiator hose after like 15 minutes of idle. I plugged in my old Snap On Diagnosis computer through the OBD2 and it was reading up to 208 degrees Fahrenheit. But my guage now read at half, as if everything was normal. I noticed my radiator fan was not on, and the thermostat was not active since the coolant was not flowing... I blasted the A/C and both fans blasted on, and the thermostat opened up and coolant flowed. The engine temp dropped down back to around the 180's (degree F) Whats pissing me off is that the fan or thermostat wont turn on, on its own. It will only open up if i blast the A/C. My next plans are to replace BOTH cooling temp sensors, but im not sure if it will make a difference. I dont know what to trust or whats messed up, the temp guage, or the OBD2 readings?
Any other ideas/ help?
My car was running perfectly fine BEFORE i dropped and replaced the exhaust to the OEM for emissions...

 

[DSM1G90]

T-stat supposed to be a 196* T-stat.

Temp sensor in the radiator is ka-put why the fans aint coming on, or the relay in the box under the hood died on you to switch on the fans by themselves.

The fan switch bypasses the temp sensor in the radiator.

208 really isn't that all bad (cars needs to run hot to run effectively-running them cool isn't their thing too well), but you do need some more airflow through the radiator.

 

[joescool2008]

May be a damaged wire to the radiator temp sensor, seeing as thats fairly close to the exhaust. Oh and i would at least put the stock thermostat back in since you dont have aftermarket tuning.

 

[zcoh2gdsm]

May be a damaged wire to the radiator temp sensor, seeing as thats fairly close to the exhaust. Oh and i would at least put the stock thermostat back in since you dont have aftermarket tuning.

tune for a different thermostat? am i going crazy?

 

[ktgurl87]

May be a damaged wire to the radiator temp sensor, seeing as thats fairly close to the exhaust. Oh and i would at least put the stock thermostat back in since you dont have aftermarket tuning.

I thought both the temp sensors were right by the thermostat housing. Now I must be going crazy because I just replaced 2 sensors right there on the gst, and they were both tagged as a temp sensor.

 

[95talongirl]

I thought both the temp sensors were right by the thermostat housing. Now I must be going crazy because I just replaced 2 sensors right there on the gst, and they were both tagged as a temp sensor.

Yup, they call them both coolant temp sensors. However, one if for the gauge and one is for the computer.

And you're correct... they are both on the tstat housing.

He may be referring to the fan relay... and they typically come on around 210-215ish from what I've with my car.

 

[ktgurl87]

So what is he talking about that runs close to the exhaust? Unless he's talking about the fan wiring itself?

 

[007jimmy]

Why did you get a lower T-stat. That doesn't do anything for overheating. It just takes the car longer to warm up. The ECU needs to see a certain temp to achieve closed loop operation. A colder T-stat might need some sort of tuning. For example DSMlink has a coolant offset feature to get the ECU to closed loop. As for the fans not coming on, let the car idle with the OBD reader and see if the fan kicks on around @210*. Check both rad hoses to see if they are hot and to see if the rad has cold spots (unplug fan when you do this!).

 

[boost97gst]

T-stat supposed to be a 196* T-stat.

Temp sensor in the radiator is ka-put why the fans aint coming on, or the relay in the box under the hood died on you to switch on the fans by themselves.

The fan switch bypasses the temp sensor in the radiator.

208 really isn't that all bad (cars needs to run hot to run effectively-running them cool isn't their thing too well), but you do need some more airflow through the radiator.

THank you for posting that. There is some myth always out there that if you run your car cooler it runs better. This is entirely false. I know im a bit off topic here but i wanted to reiterate the point this guy made. My 2g with new stock tstat sits around 210 or so according to link. These engines are meant to be operated most efficiently at a certain temperature. They didnt just pull it out of their hat and say "thats a good temp" .
OP: I would check relay and temp sensors all around. Also if you have link, manually turn on fans to rule out the relay and narrow it down to a signal problem.

 

[JDNN]

i have the same problem with my 98 only 1 fan will go on specially when a/c is on but i never got the chance to fix mind

 

[AFG-DSM2g]

I was told the oem thermostat is at 180*, and the normal operating temp is suppose to be around 190*?
Also forgot to add, my temp guage would show at about 75%-80% up when the obd2 read above 190* before i did the thermostat change.