Hey Guys I recently wrote about my coolant problem boiling over and trying to figure out what is wrong since my car is reaching 260 degrees. Well my digital gauge is reading 95 degrees and a little up and my analog is reading 185+ degrees and rising when I turn on the car. Could this be the Electronic Coolant Temperature Sensor (ECT)....if so...Where the heck is it? Is that the sensor thats attached to the bottom of the water pump?!? My fans arent kicking on and im wondering if thats the reason why my coolant is boiling and blowing my hoses off.

 

The PCM uses the temp sensor on the front of the water pump to control the cooling fans.

Also, an easy way to purge the air from the cooling system. Remove the surge tank cap. Bring the engine up to temp, so the thermostat is open. Rev the engine to around 2000 rpms. While still reving pour coolant into the surge tank and put the cap back on.

 

You are all over it for me :-). Thanks.

 

Okay problem...I need to find the Engine Temperature Sensor that controls my fans...its not the one on the Waterpump thats the Coolant Temperature sensor...where can I find the ETS?!?

 

my understanding is the PCM gets its temp reading from that sensor to turn the fans on/off.

 

Well my mechanical temp gauge is right...and my fans arent kicking on. The digital gauge isnt synching up with it. They are a 100 degrees off. I was told that the Electronic Temperature Sensor (ECT) was what controlled the fans and that it had to be replaced yet I cant find it anywhere. Is that right? I just need to get those synched up and get my fans running.

 

I'm assuming it worked before your teardown. If you didn't damage or remove the sensor, it may just be a bad connection.

 

read what I just wrote above if you didnt already.....Im wondering if I got water on/in it

What I bought at Auto Zone was a Temperature Switch Sensor

 

First, did you bleed the air out of the engine, engine runnning, using the bleeder screw on the t-stat housing? If not you won't get the air out.
Do it 3 times, last time at operating temp and keep refilling the surge tank as necessary. Turn on the A/C and do fans come on?

 

bled the system. And no...no fans period.

I turned on the heat and no hot air. Now im thinking the thermostat is sticking.

Im going to replace the thermostat and the Coolant Temp Sensor on the Water Pump. Then if that doesnt work im going to move to all the fan sensors and relays.

Taking it step by step.

 

It sounds like two separate problems. Fan should come on with the A/C on regardless of engine temp. Check fan relay first as they fail more often than the fans.

No hot air from heater means coolant is not circulating. Are heater hoses both getting hot? Are you positive you got all of the air bled out of the motor at the bleeder screw and system is full?? T-stat is possible but unlikely, what is likely is water pump has failed (broken shaft or gear) if your system is full but no coolant circulating.

 

Side of the block, passenger side towards front of motor.

 

You did reinstall the water pump's drive coupler?

 

That sounds like the engine block heater. The analog gauge temp sensor is in the passenger side head.

 

Thanks for correcting me. I meant to say head, not block. Guess I had a mental block. Duh!

 

With the a/c off, Engine Coolant Temp Sensor controls the fans and on the LT Motors it's on the pump - GM has used Yellow and Black for it's leads on pretty much everything they've made (and continue to make) so if you can find those, you've found the Sensor you want. Specs are something like 217 - 219 for the main and 226 or so for the Secondary, but I don't have them handy. With the a/c on, PCM will ground both relays when the Pressure Sensor on the high pressure line indicates 150 psi (which means the refrigerant is about 90 degrees at the Condensor). The signal would be in the neighborhood of 1.5 volts. Switch is three wires with a 5 volt reference from the PCM, the return and then a ground. You can backprobe the harness and figure out which is which, but I don't recommend you poke any holes in the wiring.

Better to troubleshoot all of this with a scanner as that will also capture the a/c signal and the air temp (which should be about the same as the coolant temp and the outside air temp after it's sat overnight). If your digital is off, it could also be the PCM. You can jumper the Sensor leads together and that should generate about 300 degrees on the Digital Display. With it disconnected, it should come up Low or -32. Doing either may set a code, so you'll have to clear it. You can also check your replacement against the one installed by reading the resistance of both after the engine has sat overnight. They should be close. Then simply plug in the new one and turn the key on, but don't start it. If the Display gives the same reading as the one installed and it's out of whack, then you know it's the PCM or the wiring and not the Sensor. You troubleshoot the wiring by disconnecting the Sensor and verifying there's 5 volts on the Yellow Wire. If not, you'll have to check it again at the PCM terminal. If it has the correct voltage and the Sensor is good, the only thing left is the PCM - assuming of course the fans and their relays are good (difficult to imagine you'd lose both relays).

 

We ran a bunch of tests. We replaced the coolant temp sensor just for the heck of it and the relays. I also went and got my A/C Freon put in. So...now when I turn on the A/C both fans work. I bled the coolant and running down the road my car is fine 194-200 degrees steady where ever I drive. If I sit my car and idle it will go up like normal but when it hits 218 degrees....still no fans coming on.....and then it just keeps climbing and climbing and climbing with no fans. The only way to cool it then is to turn on the A/C and now since that is charged both fans come on and the engine cools.

So I have to figure out why they arent coming on at 218 degrees. I dont think a cam install would change the computer but oh well maybe it is the PCM.

Any ideas now....how do i get the PCM reprogrammed?

 

With stock tuning the cooling fans won't come on until 228/237. Mine are set at 186/196.

My recommendation for changing the fans setting would be to purchase LT1 Edit or Tunercat. Then in the future you can do your own tuning.

 

http://tunercat.com/tnr_desc/do_tc.html

http://carputing.tripod.com/9697lt1edit.htm

 

Never heard of 228/237 for the LT's - I'm pretty sure the specs are 217/226 or thereabouts - certainly someone has a shop manual???. You really need to scan it or even better, force the fans with a bi-directional scanner. There is no way to tune around a busted driver circuit, though with the fans reacting to the a/c signal the driver is ok - it's what's between the CTS signal and the driver that's wacked and a tune usually won't fix that.