Usually when my truck needs something I can watch a YouTube tutorial and replace it I’m still learning as I go and work on my truck but I put my truck in the shop not to long ago because it would not start out of nowhere and it couldn’t find anything that told me why it was happening what the mechanical did was pulled one of the wires from the ignition coil plug and wrapped electrical tape around it I’m not really sure what that did but when I picked my truck up and started driving again my truck started jerking bad when I let off the gas and you could kinda here like a clunking noise coming from the front of the truck and when I would start to go up a hill or something in overdrive or third gear my truck lost all power and you could get a rattling noise and I would have to push the gas almost all the way down for the truck to go and not to long ago I drained my radiator and cleaned it out and the jerking went away for the most part but somtimes it would do it and then go away again the rattling thing never went away but today I put a thermostat in my truck and was unaware that there wasn’t even w thermostat in the first place and my truck started jerking and clunking like it did when I got it from the shop and won’t go away and my coolant reservoir started bubbling a lot I know some people will get mad that I put all this in one thread but I think these things tie together some how due to it started and stoped jerking when I put a thermostat in and flushed the radiator and it started doing it in the first place when the mechanic shop messed with the ignition coil plug
I hope you didnt pay that knucklehead for that.
In no world did gm put extra wires into these vehicles that you can just unplug and wrap with tape and make it run better.
I think you got ripped off bad by either a real piece of **** human or an idiot.
Or maybe a combo of both.
Did he list electrical tape on the invoice?
Always start with year, model, engine etc first.
It helps everybody concentrate on trying to help your particular truck.
The temp gauge not working and no thermostat and the jerking while driving and the overheating may all be interconnected.
A missfire will cause an overheat.
Lack of coolant will make the heads and intake really hot and cause an overheat.
And all of that can foul plugs and cause a misfire that makes it overheat.
Did it have any coolant in it when you drained it or was it full of rusty water?
The oldest hillbilly nonsense repair for an overheat when they cant figure it out is to pull the thermostat and drain all of that ****** green stuff out of there and run it on tap water like granpa used to do on his friggen 1957 corn combine.
Does the cooling system have any leaks at all anywhere?
If coolant can get out, that means air can get in.
And air in the system will cause your gauge to read wrong and it will cause performance problems because of the coolant temp sensor reading steam instead of being immersed in coolant and that will cause radical and rapid changes in the fuel mix and plug fouling etc..
Are you absolutely sure that you got all of the air out of the system?
There is a procedure for doing this and you cant shortcut that procedure.
I dont remember if you can install a thermostat upside down on a gmt400.
But on many engines you can .
Welcome to the forum freind
This is why you need to be your own mechanic.
And just by being here you have taken that first step.
Years from now when you see captain electrical tape pushing a shopping cart down the road.
Give him a frozen swanson tv dinner and a book of matches and an invoice for dinner.
**** that guy.