hey there.

put my motor back in n no knocking so thats good. but as it heats up the fans dont turn on and over heats. if i unplug the sensor on the w pump housing they kick in and the engine light comes on. i replaced the sensor and no luck same thing. had a 180 thermo in there and replaced that with a 160. both ways still does the same thing. fyi i installed an electric water pump. any help is apprciated as usaul.not sure what the voltages should be at the sensor. im sure i could search the threads but too busy fixxing tranny/ oil leaks. thx again. mi.

 

93 z28 lt1 auto btw. a/c has no fluids as i broke the line.

 

is the sensor at the pump a new one? did the mechanic get the two temp sensors mixed up. there s one on the block on the driver side under the exhaust towards the back that is for the temp gage, theres one on the water pump to supply the computer with temp information so it can turn the fans on and other things. also check the fan relays in the electrical box under the hood. on the driver side. there all the same except the abs one so u can switch with one u know works and see if the problem follows or the fan starts workin.

 

The website I listed below has some good troubleshooting info. I also listed some of the possible causes of the fans not coming on and possible remedies. The best thing to do if you have the capability is to get a temperature reading from the PCM and compare it to the temperature gauge when the car is hot. That way, you can tell if the PCM and engine coolant temp sensor are seeing the same temperature as the temp gauge sender and temperature gauge and go from there.

Cooling troubleshooting :
http://shbox.com/1/4th_gen_tech2.html#cooling

POSSILBE CAUSES:
- Fan relays in fuse box are bad – You can swap them with the other three of the same type
- Coolant temperature sensor is bad – tells the PCM how hot the engine is (you already changed this)
- Temperature gauge sender is bad – tells the temp gauge how hot the engine is. Because the number of pins are differnent than the coolant temp sensor, you can't swap these.
- The voltage at either sensor is bad (I think 5 volts dc for coolant temp sensor - see website ablove)
- The PCM is not working properly or the fan settings are set at too high of a temperature setting

POSSIBLE REMEDIES:
-You can try purchasing a programmer, such as Hypertech Power Programmer III and set the fan temperatures yourself. However, if the problem is not with the fan temperature settings, then this will not fix your problem (i.e. the PCM is simply not working properly, the PCM is reading the wrong temperature, or there is a problem somewhere in the circuit). The Power Programmer has more capabilities you can read about here
http://www.hypertech-inc.com/media/manuals/aa/1126271714kkuhhvzm.pdf
- You can also rig the fans so you can manually turn them on yourself.

I’ve been having the same problem where my fan motors work, but they don’t turn on when the engine gets too hot. I addition, my radiator also has a leak and I’m waiting for a performance radiator I ordered to come in the mail. After I replace the radiator, I will re-attack my fan problem and let you know if I am successful. Good luck.

 

well said mr e and thank u i enjoy reading your stuff. keep it up and pat ur self on the back for me.

 

thx guys got it figured out....little embarressed to say.......i kept shutting the car off at 3/4 of the way up on the dash gauge (this is all while being parked in my garage). after reading ur replies i let it get closer to the red line and the first one kicked in. thats about 110 c on my gauge which converts to bout 230 so i guess thats fine. i just simply though they should come on sooner and nervous about letting it get too hot with the fresh motor.anyways i finally took it for a drive around the block and it never got to the 1/2 way mark. great.

as i dragrace the car i am interested in how to trick the pcm to turn on both fans. not necessarily when i driving down the track or on the street but maybe on the return road back or in the pits and use a battery charger. i have the water pump wired so when i turn the key backwards it will come on so something like that would be great. ive read a couple ways to do this but looking for some more input. thx mr e for the reply and u too crabman...u answer every friggin post for me. thx again. oh yeah when i took it for its first spin around the block i have other problems than the fans to worry about. check out my new thread if ya dont mind.

 

I'm glad everything worked out for you. As for me, I put in a Hypertech 160 degree thermostat and a Silla 2-Row, aluminum, cross-flow radiator ($149.95 including shipping). I only lost about half a pint of blood during the radiator installation, which is less than usual for me with automotive work. I took the car for a spin and noticed I had a leak (the car, not me). I'm not sure where exactly its leaking from and won't be able to look at it for a while.

For anyone who hasn't looked at their radiator recently, I recommend doing so because of the things that can get stuck in there. While I was replacing my radiator, I found all kinds of things that only a paleontologist could identify, such as a fossilized-looking cocoon thing with dead bugs in it.