99 2.7L 4x4 SR5 Temp gauge issues

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Does it slowly go up, or instantly when you start it up? The stock gauge, as has been described to me, simply shows cold, normal and hot. The needle on my 2000 2.7L would go basically to the middle and never move (no matter what). After my rebuild and replacement of the coolant temp sensor, it does fluctuate quite a bit now. I added an aftermarket coolant temp gauge which has helped alleviate the worry about blowing the HG.

 

Okay. When you start it up, does it instantly go to half way? If not, does it take a few seconds to minutes (depending on outside temp and how long ago you last drove it) to get to the half way mark?

 

When started cold morning, mine stays all the way down. After driving for a while, it moves up a little. When its finally "normal," it stays middle, and stays there.

 

Replace the temp sensor. It is a fairly cheap part and easy to change. Located on top of the Water Outlet (follow top radiator hose to the cylinder head).

 

Is everything else working properly?

Check the ground connection on the intake manifold. Make sure it is attached, and making a good ground. According to the diagram, that is the ground for the temp gauge (and other things as well).

 

The block ground is on the driver bottom of the block (just above the oil pan where it meets the black). That ground is for the engine to the negative terminal on the battery.

 

The Triangles (upside down) are ground points for the wiring harness.

 

The only manifold ground I can think of is on the driver side Front, just behind the power steering pump. It is right next to the fuel line that connects to the Fuel Rail (there is a small vacuum line from the fuel rail to the intake system).

 

Does the 2.7 have a temp gauge sender? IIRC the 2.7 should....butt dun quote me. I know the 3.4 for sure has two....one is the "temp sensor" (to the ecu and located in front top of cylinder next to the radiator hose inlet) and the other is the "temp gauge sender" for the gauge inside truck (located far back on the 3.4). The temp gauge sender on the 3.4 is just a one prong plug, basically a signal to the gauge inside.

I was installing charger and bumped this gauge sender and my truck's temp gauge kept bouncing and dancing....it would read high and then dive down to middle when i gave it the skinny, even though my scangauge says my water temp was fine at 179-184 degrees the whole time.

Check the 2.7 sensors diagram.

 

It has two. The other is located on the back of the cylinder head (against the firewall) and is a pain to get to.

 

I am not sure on the 99 2.7 but my 01 3.4 has the 1 prong and no plastic harness on the sender.

I got mines at o'reilly's. Axe dem that its a 'temp gauge sender' and not a 'temp sensor'.

 

Yeah I replaced the one on the front. At the time I didn't realize there were two!

 

the one for mines looks like this one....just a one prong piece...

http://www.bing.com/images/search?q...3eace299eb7b293137975c5a75e30d52o0&ajaxhist=0

the ones on rockauto show there's a plastic harness cover so you'll has to look into the harness to verify if it is 1 or 2 prongs.

GL, hope this is the fix

 

OEM Part# is

$35 89422-35010 Water Temperature Sensor

89422-35010

The Sender is a single pin (if i remember the FSM correctly) and goes in the water outlet. The "Sensor" aka switch aka sender (I don't think i've ever heard a consistent answer) is two prong on my Tacoma and is located on the back of the cylinder head.

 

If i had to replace the gauge sensor switch (2 prong on back of motor), I would disconnect the battery, disconnect the 3 plugs on the ECU and pull the harness through the firewall. release the retaining clips on the motor (for the wiring harness) and lay it over the IM to remove it from your line of sight. May help getting it off and putting the new one in.

 

It is an idiot gauge (an idiot light would have been better if Toyota had thought things through). Get a ScanGauge and put it on your steering wheel column. It will show 4 gauges at once (temp, intake air temp, mpg, horsepower, etc.). I installed an actual temp gauge and oil pressure gauge in my truck, still have a scangauge for verification (only have 900 miles on the rebuild). My temp gauge (stock) is all over the place. Sometimes it acts normal, sometimes it will go half way at 105 degrees or 175 degrees. I have stopped looking at it and use the scanguage in combination with my aftermarket gauge.

 

Don't remove the sensors as the ECU needs them. I installed an inline water temp sensor adapter in top radiator hose. They are super cheap (

Upgr8 Aluminum Water Temperature Sensor Adapter (32MM, Red)

link to the one i used off amazon here) 32mm. I used digital (1 wire to run inside the truck) and connected the power to the radio power/dim wire.

 

you could also go down to your local "China Freight", if you have one, and pick up a IR thermometer gun to "shoot" the thermostat housing or other areas of the motor for reference.