Looking for some technical advice/knowledge

Hey guys,

I've got issues with my 2009 Aveo 5 LS. Any help with pinpointing the problem would be most appreciated. I've read through the forums a bit and I've seen similar issues to what I'm looking at now but none are quite the same from what I can tell.

So I'll just lay it down:

About a month ago the oil lamp and CEL come on. I took it to the Jiffylube and: 1. coolant is low (none in the overflow tank), 2. transmission fluid looks pretty dark.
They tell me that the tranny fluid might not be a problem, I figure I'll live with it. On my way to the store for coolant, car overheats, hood starts smoking. Turns out the lower rad hose was split. Through the course of replacing it, I notice that any coolant I put in comes out a light brownish colour.
Hose is now fixed, but the CEL doesn't turn off. Loss of power when accelerating, car bucks while I'm idling, and sometimes sputters when driving it. Thought it might be the head gasket but the oil level is staying high, and the oil is not sludgy.
It's had a problem in the past with the CEL staying on that just kind of went away, and I naively (mostly wishful thinking I guess) hoped that would be the case now. Not so. The other day I get another blown hose (a heater hose, the mechanic tells me) and white smoke is coming out of it. Took it to the shop, here's the rundown:

Guy says both O2 sensors are not functioning. He replaced the hose to check the engine block pressure and he thinks it's fine. There is definitely something dark getting into the coolant, maybe the transmission fluid?

He wants to replace both O2 sensors, and do a rad flush . +he already replaced the hose --> looking at $900ish after that, then we'll go from there.

Any thoughts/insight/advice would be very helpful.
Thank you

My advice would be to send a sample the transmission fluid to one of the labs (Blackstone, etc) ASAP. IMO, you need to know if the tranny fluid has been contaminated, and needs to be flushed in order to ATTEMPT to save the transmission (no guarantees on that). If the tranny fluid has coolant in it, you need to act fast because more damage can be done with every additional mile you drive.

Why is he replacing BOTH O2 sensors (what are the DTC codes)?

There's a transmission oil cooler built into the rad. I'd suspect this is what's leaking. I would guess you'll need a new rad, and at the very least a transmission service. I'm never a huge believer in 'flushes' usually, but in this case, if your trans fluid is contaminated you'll want it completely emptied and refilled. A transmission service is just dropping the pan and changing the filter. But you'll only get about 1/3 of the fluid changed.

Thanks for the insight guys. I talked to the guy I took it to first, told him I can do the O2 sensors myself if they really need it, but I'd like to explore the cooling system problems - he said he wants the O2 sensors done first... I told him I'd let him know once I've changed them, and then took it elsewhere - the other guy says the O2 codes might be due to the engine problem, whatever it is - he is going to check on the transmission cooler. I'll give another update once I hear back from him.
Thanks again.

If your blowing hoses, and your worried about a head gasket the easiest thing to look for is cross contamination. But the transmission/coolant issue will not readily cause overheating before the transmission damage. If the head gasket is blown, you will either get coolant in your oil, or coolant in the cylinder. This can be checked by pulling the plugs and looking in the cylinders, looking for smoke from the exhaust on start up, or checking the oil level isn't climbing, frothing or changing color.

If you are burning coolant, that will likely kill your o2 sensors, and clog your cat as well.

Since I don't believe you have a transmission dipstick, I don't know that you will be able to check the fluid level (if its mixing with coolant it will go up as well). But without the testing you would not know truly what fluids are mixing where, unless you can see it.

I do have a transmission dipstick, but other than it looking kinda dark, it doesn't seem to be off. When it mixes with coolant it gets lighter and thicker correct? So I don't think it's that. Checking the oil by the dipstick also doesn't show signs of it having coolant in it (it would be light brown and sludgy also, correct?). I've now had it checked by two different mechanics. The first did an engine block pressure test and says it was alright - so that is a good sign that it's not the head gasket, right? But the second says he (I'm going to get this wrong I think) checked the spark plugs and they were wet? Which he says confirms that it is coolant getting into the engine block. I don't notice white exhaust - though I do notice a slightly different smell about the car when it's been running, maybe sweet, like they say it would smell if it was coolant? I also have a really rough idle, like the car is bucking and jerking and a pretty extreme loss of power. It sometimes dies on startup, like, it doesn't start and I have to turn the key again to get it to go, and it'll sputter every once in a while will I'm driving it.