Ok heres the scanario briefly...

LS4 with a 160* tstat installed...worked great up until i noticed once i switced to E85 my temp gauge would not register but maybe a lil above the bottom line...which on my scangauge shows 150's approx...

needle will fall on its face and not register when the temp still registered 170 or lower according to the scangauge... and then i will get a msg on my DIC screen of the car that says "A/C Power Off To Protect Engine" and my A/C will not work.....but my heat will?!?!

so im getting the opposite of a bad tstat staying open...and its def. not staying closed....

Now, if i reset the car by undoing the neg term from the battery and reconnect it...the gauge will pop back up and register...?? but its only a matter of time before it starts up again on the next drive cycle and starts to struggle to get to temp....

i do notice that even though im seeing a temp increase on the scangauge to like 170 or so while the mechanical isnt working...Its still not achieving the regular 174-188 i will see on a warm day while the gauge is working correctly....even with the 160* stat in and E85....which the 174 range is usually what a lot of guys see as a norm OT for LSx E85 cars with 160* tstats, from what ive observed...

It threw a DTC the other day indicating the engine was not able to get to optimum OT...I cleared it and went on...then the gauge sometimes will pop back up and my temps go back where they are supposed to...

coolant is where it is supposed to be and the right stuff...so dont go that low on me LOL...little past rookie on this one LOL...

but everything is going against itself here LOL...

some opinions would be great! thanks guys! and switching to a RWD or an Fbody doesnt count as an opinion! LMAO!!

P.S. im thinking its a combo of the block/coolant sensor and the tstat...is only thing i can really come up with..

 

Off the wall idea... Maybe a 160 is too low?

 

i had the same message in my dic a few times so yesterday i got my coolant flushed (factory coolant 88k miles) and had the temp sensor changed. the shop i took it to had said it was bad. i am not sure if it is that with you but i would try that. it ran fine today in 100+ degrees

 

i have changed flushed the coolant a total of once atleast by now due to the 2 tstat changes...from the factory to the 180, then the 180 to the 160....

I think its probably the coolant sensor cause i still get heat even though the tstat is demonstrating that its basically stuck open....and my coolant temps are reading much lower even on the digital gauge when the needle doesnt work....so...who knows...

 

yea I would check the sensor. I still had heat to so I knew it wasnt the tstat and I needed to change my coolant anyway.

 

Does the scan gauge your using plug into the OBD2 port? If so and its reading 170, then I would think your thermostat and sending unit is working. Maybe loose plug going to gauge? I would'nt think it has anything to do with E85. I could be wrong I've been wrong before and I'll be wrong again. Its suppose to burn cooler, but your seeing 170 on the scan gauge.