Allright, so here's whats going on. The car has been running flawless for about 5-700 miles since the 6262 turbo kit has been put on. Recently under normal driving conditions the temp gauge would shoot all the way to hot. If I turn on the heat the temp comes right back down to normal.

I finally got a chance to look at the car in more detail today. I got it to where the temp gauge was heading all the way in hot and used one of those temp gauges you can shoot at stuff. And it's reading right at 190 degrees whether the gauge says it's hot or not.

So basically the gauge seems to have a mind of it's own and the cars not actually overheating.

What should I be looking for? Seems like all the grounds are in-tact, but maybe i'm missing something. Can the gauge itself be bad?

 

Sounds like you might have a sticking thermostat. You'd have to measure the temperature right at the thermostat housing since that's where the gauge sensor is.

 

I've shot it right at where the thermostat is and the pipes and the block itself. There all reaidng pretty close. But right at the thermostat it's reading 190 degrees and the gauge will be showing full hot. If I turn on the heater the gauge will come back down and the thermostat will still read right around 190 via the temp gun thing.

So there's nothing wrong with the cooling system, pretty sure it's electrical.

 

I have this same issue and haven't sourced the problem yet, however I have logged temp on evoscan and temp stays around 190

 

I have not had this issue on the evo but i have on many past cars. From my experience:

When this happened, it drove me nuts; the temp would sky rocket on the gauge, and as soon as i turned the heating on it would go back to normal.

I started small by replacing, thermostat, then water pump, coolant, fans, thermostat sensor, and eventually radiator and hoses.

After many trial and error practices, readings, and frustration, i changed out my temp guage, and viola... the problem is fixed. All this time i too was taking manual readings and it read that the temps were fine; but me being paranoid i essentially replaced all components of the cooling system.

All and all, the moral of the story here is that, with 3 of my past vehicles i have ran into the same exact problem, all in which the temp read good by taking readings manually but my gauge was reading hi. Replaced the gauge and all was well.

I would start very small and work from there. If you can grab another gauge to read the temps. The fact that your taking readings manually and all says everything is ok should indicate an issue with the gauge itself.

Every car is different though, just wanted to share my experience. Good luck.

 

Hooked up the Ohm meter to the sensor and it just slowly made it's way down to zero. So i'm fairly confident the sensor is bad. Going to order one and see what happens.

 

sounds like classic symptoms of a broken thermostat in the closed position. A broken t-stat is easy to replace and is often the starting point of diagnosing the problem. As suggested above, a bad gauge/sensor is another plausible culprit.

If the t-stat is stuck closed, coolant is not circulating between the engine and radiator, which is the mechanism for maintaining constant operating temp. The coolant on the radiator side (including that which is in the upper rad pipe) is going to be at a lower temp since it is not in contact with the engine itself, which generates heat from its moving parts. Since there is no circulation of the coolant, the temp rises according to the dash gauge. That temp falls when the heat is turned on since the source of the heat is the hot coolant. Take the opposite scenario for example...if the t-stat breaks in the open position, you see no overheating, but the heat will not work very well. This is because the coolant is constantly circulating between the engine and radiator, producing a lower overall coolant temp, and less heat to draw for heating the inside of the car.

If you let the problem go farther you will be dealing with warping engine components due to improper cooling. Replace the thermostat and that should solve the issue. If not you will need to rule out other components in your cooling system...such as a bad gauge, as the guy above suggested. DO NOT assume the gauge is bad just because the aftermarket gauge is normal (not sure of the temperature source of oem vs that aftermarket gauge) ...you must replace or test your current t-stat first...its the best and cheapest place to start

 

Right, but i'm not just using an aftermarket gauge. I'm using one of those temp guns that you can point at something and get the temperature.

When aimed at the thermostat it reads 190 degrees and the gauge is reading hot. Turn on the heat(really just the fan in general) and the gauge comes down to normal, but the temp at the thermostat is still 190 degrees.

I guess I don't understand how it could be the thermostat. The car never actually overheats.

The gauge can go from normal to hot in a matter of 10 seconds and than come down in a matter of 10 seconds with the fan on. Basically the cooling system is fine, the problem is somewhere else. Hopefully changing the sender (sensor) will fix the problem.

 

Sounds like it could be the sensor in your case after reading more about how you've diagnosed it. Sensor is cheap enough to replace and see if it fixes it. Hopefully you problem isn't with the cluster itself.

 

My OEM gauge does this but instead, the temp drops. The cars warms up as normal and will randomly, sometimes with throttle drop down to "C". I replaced the T-stat, didn't fix it. I'm thinking bad sensor.

 

Check your grounds first. When the grounds start going bad the gauge shoots up when you fan comes on. But only past a certain temp. When ou turn on your heater or AC your fans come on more often and it never gets to that threshold temp that makes the stock gauge go nuts.

Install and aftermarket, or DIY grounding kit first.

 

The new Sensor seems to have fixed the issue!