Temp spike, and quick RPM reduction (06 Aveo)

[BBruins12]

Hey All,

I've got two issues.


#1
A few days ago I was cruising around, with the AC on, and when I came to a stop light, my car started to over heat.
It got to about 7/8 before I turned around and went home.

I made it home safely, checked my coolant reservoir, and attributed it to the fact that it's been 95 and sunny the last few days, and my car has been parked in direct sunlight.

I had the same issue yesterday, but when I turned off the AC and turned on the heat it helped. When the heat was off I was heating up at a stop again.

I checked the relays, and they seem to be working fine, the fan motor isn't gone because THAT'S kicking on when it needs to, and I replaced the Thermostat not even 10K ago. The hose running from the thermostat to the radiator gets rock hard, and hot when this happens. I've also JUST replaced the reservoir cap.

I didn't think it would be the thermostat, because it's not overheating RIGHT away, but I bought another one, and I'm going to replace it anyway (it was like $4) and flush my coolant system.

#2
When I have the car in neutral and rev the engine to about 3K RPM it drops back down to 5-700 in half the time it usually takes.

I'm in desperate need of an oil change, so I'll do that, and see if it helps... and if not I'll bring it back to the guy who replaced the timing/serpentine belts and have him check the tension to see if there's too much resistance.

I'm writing this because I want to take any advice that you guys can give regarding these issues. I'm going to do everything I mentioned ANYWAY just for good measure...but if there's something I overlooked... I don't want to be stuck mking larger repairs.


Thanks as always!
-K

[petrified.rabbit]

might be a bad thermostat. but are your radiator fans kicking on?

[BBruins12]

"I checked the relays, and they seem to be working fine, the fan motor isn't gone because THAT'S kicking on when it needs to..."

Yeah I checked that, I'm going to flush my coolant and replace the thermostat tomorrow.

[avguy]

Was the timing belt work done very recently? If so, perhaps he didn't burp all the air out. If it wasn't changed recently, then are you saying the heat gauge had been normal (just below half way up), and then one day it suddenly went all the way up? That would imply a leak - enough that you should see it on the ground.
Don't know what #2 is all about, but what does "desperate need of an oil change" mean? You can check the tension on the serp belt yourself, and the timing belt is auto-tensioned (assuming he adjusted/backed-off the water pump correctly).

[BBruins12]

Desperate need of an oil change means I'm WAY over 3K/3 months to the point that I don't even know how over.

There isn't a leak anywhere that I can see. I looked where my car was parked when I came back to the driveway, but all that had been there was the condensation from the AC Unit (which I noticed when I left), that had evaporated by the time I got back to the driveway.

Edit:
The Timing belt was done in August, as well as the valve cover gasket, the plugs and wires, and the thermostat/housing

I'm going to bring it back to the guy who did my timing belt to have him check the tension.

As said in my original post: "The hose running from the thermostat to the radiator gets rock hard, and hot when this happens."

It's like someone inflated it (like a ball)... which makes me think it IS the thermostat...so you see why I'm torn.

[avguy]

You didn't say if this went from normal to overheating gradually or all at once. And I'm assuming that you would have mentioned if it was running bad with visible white smoke. So it sounds like the t-stat could be the culprit. But regardless of what it is, you need to get it fixed asap because these engines often blow head gaskets and/or warp heads on big overheats.
On the oil, do youself a favor and read some information about current oil technology. You can find lots of stuff on this and they all say the same thing. 5K mile OCI is consertative these days - many auto makers are using 7.5K. It took me a while to come around to this - something about an old dog being slow to learn a new trick

[BBruins12]

You didn't say if this went from normal to overheating gradually or all at once. And I'm assuming that you would have mentioned if it was running bad with visible white smoke.

Yeah, no white smoke, and it's running almost like a dream....sort of haha.

Nah, she's running fine, it happens after 8 to 12 minutes of driving, and it seems to only be happening when my AC is on...

Like I said, I'm going to pop the thermostat and replace it, run water throught the coolant system for a bit to clean it out, then put some different coolant in it.

I'll check out the new oil standards as well. I was using Quaker State Torque, as it was the least expensive Full Syn oil that was GM409 cert., but I picked up some Casteroil Edge and a FRAM Gold filter... so I'll check that out.

I was considering the Transmission fluid trick, but don't want to do that, then forget that I put it in, and not change my oil quickly enough...annnnd I've gone of topic,


Edit:
Reservoir cap started steaming, and bubbling happened... yup... thermostat.

Edit to the Edit:
Replaced the thermostat... WRECKED the metal housing which refused to come off... but that was the issue. It's only 9 months old, so that'll be sent back.