Water overflows at 180F.

[wmburns]

Pictures of the RH temperature sensor

The Battery negative is grounded to the chassis. So does it really make a difference for a test to use the battery negative or the chassis? Not really other than sometimes it is easier to get a good electrical connection to the battery negative.

Not a good idea to run a wire straight to the fan. This can be fixed but now that we know that both speeds of the fan itself are good, more tests are needed.

Post a picture of the "other" temperature sensor on the intake manifold. The one on the right side of the intake manifold crossover. Make sure to get the wires and connector.

Consider bleeding the air out from the top of the tee. Let's see if that gives more reasonable temperature readings. Wait until the system is pressurized and crack the fittings at the highest point. This will have to be redone each time the coolant system is opened.

OBTW; there are better ways to force the fan to run than running a direct jumper. Consider also that a direct jumper will run the fan ALL OF THE TIME. Even when the AC is on, the PCM turns the fan off when the car's speed is above 45 MPH.

 

[Rickyll7]

What gauge wires did you use?

 

[patman0911]

Since you said the fan does come on with the A/C, then if you want to force the fan to run, just turn the A/C or defrost on - no need for jumpers.

I would start over. Take that tee out and just put the factory sensor back in by itself and see if you get reasonable looking readings. You can put the aftermarket sensor in by itself too and see if it gives sensible readings too.

If you're dead set on using the aftermarket gauge then you'll need to find an alternate location to place the sensor, or live without the factory gauge as I don't think you'll ever get reliable readings with the current setup and what's the point of having two temperature gauges if you can't trust either one of them?

It would help if you had an OBDII scanner that could read out the temperature as reported by the PCM too so you can see what the water temp really is and see if the gauge(s) track correctly with it.

Once you get temperature readings that are reliable, then you can start figuring out why it's over flowing.

(edit: corrected sensor locations - sorry for any confusion)

Just to be clear, the PCM gets its temp data from the sensor on the driver's side of the manifold and that's the data by which the PCM determines fuel injection strategies and when to turn the radiator fan on and off. On a NPI car, the sensor on the passenger's side does nothing other than drive the temp gauge in the dash - the car doesn't know or care what it's doing. PI cars don't have the second sensor and in those cars, the temp gauge on the dash is driven by the PCM.

The PCM should turn the fan on at 221 degrees and it should run until the temp drops back down to around (IIRC) 200 degrees. The high speed fan doesn't come on until somewhere around 230 degrees.

 

[patman0911]

As pointed out to me in another thread, I had the sensor locations backwards.

That explains why your fan isn't coming on though, the PCM is reading low along with your mechanical gauge in that tee and it's never seeing the 221 degrees needed to turn the fan on.

 

[trombonedemon]

I see a couple of issues here. The height of the tee is so great, there is a real possibility of air being trapped in the tee. This will cause the sensor to read the temperature of the AIR and not the COOLANT. Some method will be needed to ensure the sensor is actually touching the coolant or the PCM will never get a true read.

This may explain why it is coolant is venting at 180 degrees as the actual temperature is much higher. Consider under normal conditions, 180 is not high enough for the PCM to even call for the fan to run.

This also points out how all of this stuff has to work together. If a lower temperature t-stat is used but the PCM is not re-programmed, then the car will never reach the correct operating temperature. This has the t-stat opening too soon and the fan never runs. The results will be wild temperature swings depending upon outside temperatures and how the car is operated (AC on/off, how fast ect).

There is also no indication of the fan tests. The low speed fan uses the R/O wire. The high speed is O/LB. The ground return is BK (black). Disconnect the fan connection. Jump the R/O and black wires directly to 12 volts. The low speed fan should run.

Next jump the O/LB and Black wires directly to 12 Volts, the high speed fan should run. There should be an obvious difference in fan speed. Post the results.

If the fan only has two wire colors, then the wrong fan has been used.

Once we have the results, will need additional tests to further narrow the problem down as I think there is more than one.

On first impression, my vote is the primary problem is air in the tee resulting in a chronically low sensor reading. The PCM never calls for the fan to run and a slow overheat is the result.

Consider using the drain taps on the side of the block for the mechanical temperature guage. Restore the PCM temperture sensor to its original location. This will have the tip of the sensor in the coolant stream thus ensuring an accurate reading.

Plus 10, Burns explanation is thorough and precise, that t setup is garbage. Also consider to Order yourself a metal adapter for the mechanical temp gauge, it goes in place of a piece of your upper radiator hose, very acuarate. You can find one on ebay, just measure your hose inner diameter (35 mm if I remember correctly, do it yourself though) and 20 bucks and some JB weld your good. Oh you need to drill the hole a bit bigger for the temp male part. Your problem seems simple, your temp gauge for the car and the mechanical gauge are reading the same temps. Best of luck.

 

[ErniesRedGT]

I've tried everything I can possibly try to get the fan to come on under normal conditions. I cleaned all of the sensor connections and I bled the air out of the t fitting. I ran the car with the fan hooked up to the battery for a long time, and it ran great. So I tried to hook up the fan to the interior fuse box using a fuse adaptor that lets you add an accessory to a fuse location, and it got way too hot. When I tried using the fuse box under the hood it didn't get hot, but the problem is it seems to always have power and I'm trying to find something that will turn the fan on with only the ignition. By the way, I'm using 12gauge wire, so the wiring is not the problem. Please help me find a reliable power source that will turn on and off with the ignition to wire the fan to. Any help is appreciated.

 

[nyuk98gt]

ErniesRedGT:

I suggest you give the air bleeding routine another try (no flame intended) because you will be surprised how much air gets in the system when you change the coolant.

Can you datalog? What is the sensor reporting as temperature? If it is not seeing the coolant then the PCM will not command the fan to come on. I agree with the other fellow who recommended moving your ECT sensor to the block and then you can install your aftermarket gauge sensor in the crossover (like you have done).

If you wire up the fan to run all the time that the engine is running then the fan will fail prematurely. You will end up replacing the fan. Also, the fan will be fighting the airflow through the radiator at highway speeds. Not fighting so much as the airflow will cause the fan to run faster and this will damage the fan motor. In summary, if you want to control the fan then you need to (a) find a switched source and (b) use a manual on/off switch so you can turn the fan off at higher road speeds. I'll stop nagging but the better solution is to move the ECT sensor to the block. Plenty of people have done this when they have swapped the intake from NPI to PI and the second sensor boss is not on the crossover.

GL and please post back with an update.

Chris

 

[trombonedemon]

Put the stock setup back just to see whats going on. The only way an aftermarket temp gauge is going to give a correct reading is if its reading the same temp as the stock therefore the gauge must be directly in the coolant, if there is air in you coolant/degas bottle then there is air in your T setup. Replace w/stock and go from there. I have a 2000 gt and the fan comes on exactly 210 degress Farenheight. Stays at 180 when on the highway from wind and coolant/thermostat. When I accidently unplugged the temp sensor while the car was running, it threw a code and the fan would not stop. I think your temp sensor and fan are fine just put your stock setup back and find a more accurate setup!