Hey guys im fairly new to this site and this is my first post.

I have an 87 Toyota pickup with only 140K miles. one day i took my truck out camping and at one point as i was going up hill i noticed my temp gauge jumping all over the place which was weird because I've never had an issue as long as ive had it. i pull over checked the radiator, it seemed to be fine but i did have to add a couple water bottles of water. After that my temp gauge got suck in the middle at all times. went you turn the ignition off it falls down but as soon as you turn it back on it goes to warm, so i ended up replacing al the temp sensors that where available the problem persisted i swapped out my cluster and that when the gauge showed that truck was at red( overheating ) however the engine ran fine the fan clutch came on and off as it should. so i began replacing parts left and right, replaced radiator, water pump, two stage thermostat, all the hoses, Still the gauge would reach red hot as if its running really hot but still i never saw water boil.So eventually i rebuild the engine ( with my dad who is a mechanic with over 25 years of experience ) the machine shop that i took the head too said there where no cracks found on the head and he told me it looks good( i still resurfaced it). So after i rebuild the engine and replaced pretty much every part can potentially cause over heating i STILL have the same issue , i tried multiple cluster and no change. Again the engine runs fine as it should i cant see any exhaust smoke or boiling water. I think there may be a electrical problem but im clueless. Ive basically read every thread that i could find for this issue and done all that i could but this problem is frustrating me so MUCH! If any one has any advise or maybe had the same issue please help me !!! Thank You!

 

Definitely sounds like an electrical issue based on everything you've replaced. Maybe a faulty ground or something. Are any of your other gauges acting up? I would trace all the wires from the cluster to make sure the factory harness isnt corroded amd all grounds are securely connected.

goodluck. I hate electrical gremlins!

 

Find yourself someone who has a Infrared heat gun and check things out.

The temperature sending unit grounds in the manifold so any sealant can cause problems

Also a loose connection at the sending unit

Just install a aftermarket temp gauge

I would lean more toward a problem on the senor end then in the cab

 

I had a slew of those cylindrical temp sensors go bad on me, right next to the head on the intake manifold. How many of those have you gone thru? it sounds like a hotrod fix is in order, from autometer.

 

Hey thanks for all the replies!

I have already used an inafred gun and all the temperature checks out good. and all the other augers seem to be working fine

and ive replaced the temp gauge like 3 times with an oem replacement..

I have already bought an aftermarket gauge, where would be a good place to tap it into?

im still going to go through all the wires and ground!Thanks for the help!

 

It's sounds like it may be an electrical problem. But, have you taken the infrared gun and pointed it all over the radiator to make sure coolant is flowing through it? And have you also checked to make sure the fan clutch is working properly? "looking like it is working" and working properly are two different things.

 

Yes ive gone through the whole cooling system with the gun,temperature is t pretty much the same all around. and i have replaced the fan clutch with a new Aisin so that should be ok.

 

Ok my next question would be... are you replacing the right coolant temp sensor? There is one that goes to the ecu and one that goes to the guage.

ECU coolant temp sensor (front of motor under intake plenum, green plug)
Gauge coolant temp sensor (in lower intake plenum next to valve cover)

 

well I've basically replaced both sensors, I made sure that I got the right ones, today I installed my aftermarket gauge and I the the sensor in the ecu location wich is on the the thermostat housing, the temperature on the aftermarket gauge shows 200-220 Fahrenheit and when it idles it at 190..

 

Have you though about just putting a auxiliary temp gauge and sensor in?

 

This is Ok;

Modern engines run hotter than back in the day. If it bothers you change to a 180 degree thermostat.