Ok, my 99 Camaro 3800 has been overheating off and on for a month or two. It was weird because while driving it would get around 250 and then suddenly drop to around 215 in an instant. Always stayed around 205 in the past. Thought it was the thermostat, so replaced the factory 195 with a 180. Worked for a LITTLE bit, but soon began overheating again. I had the entire system flushed out and was told that there were no problems. Again, worked for a bit longer, but soon started overheating again. So I figured maybe the thermostat might be sticking since I replaced it before the flush; Replaced it and still overheated. One night as I was driving home, I had to pull over because it hit 260. Popped the hood and noticed the sound of coolant "chugging" or "gurgling" in the top radiator hose. Was hot as hell of course, but I noticed the bottom radiator hose was not as hot as it should be. I could keep my hand on it without getting burned. Made me think that it might be an issue with pressure, since the bottom is the return hose. Bled the air out, still overheated. Noticed fans were not kicking on, so rigged a switch up to the relay and forced both to come on with a switch; Still overheated. Replaced the water pump, still overheated. Replaced the radiator cap and it is still overheating, even after I bled the air out again. It is not throwing any codes at all. I am just totally baffled by this and have no idea what else to do. The coolant is all fresh and not gummed up or discolored. Oh, and not once has it ever leaked. Heat has always been constantly hot. If anyone has any more ideas, please share, because I am at a loss now.

 

Sounds like you may have a partially plugged hose, or a thermostat that is not functioning well... Have you or a previous owner been using any of that stop leak garbage in the cooling system? (big no-no!) If so, you know your problem, which you can use some super-flush to get it out -- will take multiple treatments. I know you said the coolant is not discolored, but could there still be a build-up in the system? You can always try squeezing all the rubber hoses along the length to ensure no obstructions. Also look for kinks or heat warping. Do you know how the last flush was done? You're sure the fans are currently working and not seized-up?

Also, when you put the heat on high -- do you get solid heat out of it now?

 

I took it to Midas to get flushed, took them a while so I would assume they did it correct. I know none of that stop-leak crap was used in it. The heat is always constantly hot. As for the fans, they are working; Set them up to a toggle switch and they are both blowing air. No kinks in the hoses, they all look in decent condition. As I said, I am at a loss on this.

 

Got the overheating issue taken care of. But unfortunately now the coolant is leaking and forming a puddle under the oil pan. If it's not one thing it's another, eh?

 

^ So what was the solution?

 

mine leaked down the pan, found it coming from the cracked plastic bypass hose connected to the tensioner. Might be something to check. Might also be the coolant drain sensor plugs leaking too.

 

The overheating was caused by a couple things. My temp sensor was bad, radiator cap was bad and there was a bunch of air in the lines. I believe I have found the location of the leak. There is a spot above and to the left of the water pump, when you face the engine, that is leaking. I'm unsure what the part is called, but it is a rubber 90 degree elbow. It is steadily dripping from around that seal. Started leaking as soon as I put coolant in my radiator. Pics will soon follow, just been busy recently.

 

that is the plastic bypass hose that goes into the tensioner

 

Yup, go to the parts store help section and get two of them for like $5.00!

 

Replaced the 2 plastic bypass hoses and bled the air out. Car is running amazing now with no more leaks. Thank you to everyone for the help.