flushed coolant out today and now the temp gauges has a red light on and the needle is pegged at cold.

Anyone know what I did??

thanks

 

You have a air pocket and the temp sender is not immersed in coolant thus no temp reading on the gauge but the temp unit for the ECU is r in coolant and is reading the overheating of the engine.
You need to re-bleed the cooling system.

 

right again Spike555!!!!!!!! I also hit the cats and found a heat shield that was falling off on the drivers side cat. took it all the way off and it has reduced the knock considerably.

thanks

 

You don't want to drive for long without the heat shields, better fix the old ones and reinstall them.
What year is your truck, how many miles on it, where is the bleed screw located and have you ever replaced the t/stat?

 

Glad to her it.
Remember to always KISS when working on cars.

K eep
I t
S imple
S tupid