Thermostat problem?

[SoCalGSX]

So i have a problem and i believe it might be the thermostat but am unsure. Street driving there is no issue at all. When i drive on the highway at 65 to 70 mph for about 15 to 20 minutes my temp gauge goes to about 3/4 and i then turn the heat all the way up but leave the fan off and it starts to cool down to normal. Could that be the thermostat not completely opening? At first i thought maybe a fan issue but i can hear it coming on and my a/c and heater both operate correctly. Any input would be appreciated.

 

[ThEDrEaMEnDeR]

sounds lie the thermo to me i would just change it

 

[SoCalGSX]

Thanks for the imput. I will do that and let you know how it turns out. Will take a few days because i need to order the part >.<

I have one more question that i haven't been able to find the answer to. I have an oil leak which looks to be coming from the OFH plug. I am going to degrease the engine tomorrow and inspect the area to see if it is coming from there or somewhere else. If it is the plug is that something that i can put a little German torque on or is that a torque specific piece and should really replace the whole housing? Thank you in advance.

 

[my dreamt dsm]

Once again, try the free stuff first.
Is your reservoir full when you come to a stop and start the car hours later. Bad radiator cap.
Is the bottom radiator hose cooler then the top one, if so...
Take out thermostat then put it in boiling water to see if it opens.
Second. Stick a girl's hair pin(bobby pin) into the thermo fan sensor to see if it turn on. If not it's faulty. Reason why, when you drive is cools the radiator down. The fan comes and cool when you stop, that's why when you stop it goes up!

Many people always buy things to fix when they can try the free stuff first. Keep that in mind next time.
Tell us how it goes, subscribed!

 

[SoCalGSX]

Hey just wanted to say thanks again for the help. Pulled the thermostat out and the first thing i noticed was two holes that looked to have been drilled out after buying. Weird i thought but o well on with the test. Put it in boil water and it opened on the top side but not the bottom side. Bought a new thermo and now its working perfectly. Actually warms up a little faster and never goes up half on the gauge. Thanks again!