I have a 2000 3.4 ATX. It overheated today and from what I was told it got real hot. He said the temp needle was on the top red line for around 5 min or so after he shut it off. He drove it home shutting it off and letting it cool down and so on. The radiator was full when it got here. I do not think the fan was running tho. It didn't throw any codes. There is no water in the oil and I ran a compression test and all were right around 150. There is oil in the water but i think that is leftovers from the LIM gasket that has been replaced. Now comes the strange part its all cooled down now. with no plugs in it cranks fine spins good and fast but when you put in just 1 plug (any plug) it tries to crank over but the starter spins out (goes zing) like the starter is going out. We never had any problems out of the starter till now. I hooked up my 200 amp charger to it and tried giving it a boost of juice and it does the same thing. Any help, suggestions or test I can run would be GREATLY appreciated.
1 other thing I put my finger over the number 5 cylinder (with all the plugs out and some creative squeezing of the hand lol) and crank it and after about 2 spins it starts blowing worm to hot air out.
Thank you.

 

Ok the starter was bad. The thermostat went out that is what caused the over heating. Everything is fixed now. Chevy says there thermostats are designed to go out in the open position (a fail safe) but its a fail safe that did not work! I have worked on many cars and trucks and this thing sure is a pain in the $%$ to work on. Why would they put the thermostat where it is so hard to get to?

 

The 3400 is a little bit of a pain to get to, I do agree with that haha

Flush the coolant about every 2-3 years, not the 5 years GM recommends. The coolant can break down and get sludgy and that could have made your thermostat stick.

 

Not sure how different the 3400 you have is from the 3800 in mine... but
I thought changing out the thermostat was pretty simple

 

In the 3400 it's a PITA. You have to basically take the air intake apart to get working room and then the rear bolt for the housing is under the exhaust cross-over so it's not easy to remove. Then the thermostat is buried.

Here's a video on replacing it if you want to see how tight it is.

 

I think that was the hardest thermostat that I have ever changed. I do think they could have come up with a better design. The starter was easy. I flushed the coolant real good and got all the oil out of it. also something else weird, if you put on the radiator cap the way it says it will over heat. You have to put it on the other way.

 

It did it again. It was not overheating and was running fine till today. It started overheating again. I put Polor antifreeze in it could that be it? Its green anti freeze. It started to overheat and heater went cold I hit the gas and temp went down and started heating. About 30 miles later it did it again but this time did not come down. When I changed the thermostat I flushed the system. I gotta have this car running PLEASE HELP!

 

Could it be something to do with the cap or the hose running from the res to the radiator. I did notice when I put the radiator cap on with the arrow pointing to the hose it overheated but when I turned it around it was fine.

 

Did you bleed the system?

 

How? I cracked open the valve on the line going to the heater core and let some air out. How do I do it properly?