09 TC with MPx full exhaust, Hahn intake, Injen hot side piping, Trifecta tune for power mods.

I heard a loud POP while under what I'd guess is no more than 50% throttle. I experienced an immediate loss of boost, but an otherwise drive-able car for the 10 minutes it took for me to drive home. I figured I popped a connector which is exactly what it sounded like. However all the hoses seemed in place after a brief inspection.

I threw MAF malfunction codes, P0100 and P0102.

After I parked the car would not idle or run at all for more than 10 seconds. The RPMs would rise and fall over and over until it stalled. Removing the MAF led to a stable idle condition but it would run extremely rich.

Despite the massive damage to the end tank I could not feel or see it from under the car. I wasted time looking everywhere else before I finally just removed the bumper (messing with the wastegate a lot due to the TSB that somewhat described the condition I was having). I was shocked when I finally saw it.

I immediately ordered an MPx replacement due to cost and location (takes one day to get to me).



All better. The fit isn't 100% with the undercarriage plastic covers. It is minor enough that I didn't feel like making the trims on the fins that would make it fit. The downside is that 4 screws are unable to line up with the bumper and plastic cover (2 on each side) but it seems to have zero effect on the rigidity of it so I don't think I'll bother.

On a weird side note - when I installed the MPx exhaust I broke the old O2 sensor. Since then I just left it out since I thought it only measured the effectiveness of the cat which I no longer had. The car ran fine. However right after I installed the new intercooler the car would run awesome, then go into limp mode, then awesome, then limp mode over and over again. I threw a P0036 code which basically is a result of it just being missing. But I figured since it ran fine beforehand that something else must be up.

I hooked up a new O2 and the car runs perfect. ??? Why now? Then it got weirder. Before I was running exactly 20 psi at peak. After I put in the O2 sensor I run 23 now. Hooray! But...? I just don't know.

After all that I'm still throwing a P0100 code for MAF circuit malfunction. I replaced the MAF for good measure since I wanted to anyway but it's still happening. Since that was the same code I threw when I had what was essentially a (massive) leak, maybe it's still a leak. I don't know maybe somebody here has an idea.

I basically wanted to write this so people could see how the car behaved with a blown endtank and the codes given and whatnot!

 

Damn! I havent seen one that messed up in awhile.

 

Lets all thank Gm for their great quality parts

 

No, the stock GM intercooler works fine with the stock GM charge pipe at the GM designed power levels. This guy is running aftermarket charge pipes and I can almost guaranty you that's what lead to the demise of the intercooler.

 

I don't know if that's a fair statement...Not that he was doing anything crazy, but he wasn't running everything stock. Why would GM make parts to handle anything other than stock? It's not their fault someone mods their car. It makes sense from a business standpoint to only make your parts to withstand normal, stock conditions.

 

The plastic was brittle and I'm positive it would have failed under stock boost eventually. I was running 5psi over of course.

Plastic endtanks are like rubber hoses, you can expect them to fail eventually its just a matter of time. I also don't like them because they are crimped on making what could have been an easier repair much more difficult and unappealing.

Just a cost thing. I've noticed a few cost-related compromises on this car already, but frankly I was expecting as much for the price. For comparison my last car was 300 hp stock but every component handled the 400 hp I was pushing for 80k miles of hard driving, endless launches (awd), doughnuts, thousands of backfires, and by the time I sold it had good compression, perfect A/F, alignment so on point it was untouchable, simply no problems of any kind. And people are well known to push it to 600+ with a fuel pump, valve springs, and good tuning and not worry too much about major malfunctions. I would not expect my Cobalt to handle that. Cars can be designed to handle more than stock (as a side effect of bullet proofing) but of course, you pay $$$ for that privilege.

I'm keeping my Cobalt at this power level probably indefinitely as my commuter. I'm very pleased with where its at for the money I put into it.

 

damn and i have a factory stock intercooler sitting in my garage i need to get rid of that has less than 1,000 miles on it.

 

I don't think it's quite fair to say plastic end tanks are guaranteed to fail. They may not take as much abuse and absolute max pressure that a cast aluminum end tank could take, but then again it depends on what the OEM plastic tanks were engineered for. In the case of the Cobalt the plastic tanks are usually fine at stock and even slightly elevated power levels, they flow very good and save weight at the very front of the car. While they can and do fail so can a welded all-aluminum intercooler.

As a side note, a few weeks after getting my car in 2008 I had a slight bit of bad luck and hit a tractor trailer tire tread that broke the lower grille and slightly dented the intercooler and later the same evening while driving up in the mountains had a large raccoon run out in front of the car at 30 mph that smashed the intercooler hard enough to crack the plastic around the mounting tabs. I eventually bought an aftermarket ZZP unit a couple years ago that's been sitting in the garage waiting to go on the car and expected the stock unit to completely give out but it never did.

Just because of that I wouldn't say it's especially strong but I also wouldn't say they're super weak and failure prone. Tons of boost pressure and colder climate have claimed a few of them but many more people have never had an issue.

 

What was your previous car? And did you buy the cobalt new? because car prices jumped quickly from the mid 90s to 2007/8ish and GM did do a bunch of R&D into the handling, just ask John Powell about it

 

On the topic of plastic end tanks, I agree they aren't always destined to fail. Many years ago, I got tuning on my Audi A4 which raised the boost from 7 to 15 PSI. I ran that for 130k before replacing the stock SMIC with a FMIC so that I could run more aggressive tuning on a bigger turbo. It was not common for the intercooler to fail on those cars from increased boost and a lot of people ran that kind of tuning.

 

I'm sorry I worded it a bit strongly. I am certain this particular one on this car was destined to fail just based on the condition of the plastic. On plastic end tanks in general I still think they are like hoses, which can and do last the life of the car sometimes but is not particularily surprising if they do fail.

Theres no way to tell what this intercooler was subjected to to make it o brittle and I have no idea how strong they are brand new. Frankly I don't like plastic of this type under constantly changing pressure on any car. The stock charge piping felt plain awful to me tbh.

 

We see more failures like this in winter. The cold temperatures make the plastic more brittle. When we see them in summer, that is just more boost pressure than it was designed for.

 

Being that I might be replacing me intercooler in the near future if I end up having some irreparable cracks, can I throw on an upgraded one like the mpx without a tune? I am assuming the airflow would be a bit different but otherwise nothing would change.

 

With an intercooler the main factors that affect how it performs is cooling efficiency and pressure drop across the core. The engine management is fairly smart so you shouldn't have any issues with that intercooler on an otherwise stock car. The computer will still be shooting for the same torque goal (engine power output) anyways, so at best you might make the same power at slightly lower boost pressure and be a touch more consistent in extreme heat.

The stock unit works pretty good at stock power levels, with my car running dead consistent passes down the quarter-mile, back-to-back-to-back in the middle of summer here in Southern California stock and with the GM Stage 1 upgrade, so I wouldn't expect to see significant (if any) power gains unless you tune the car to take advantage of the (possibly) better intercooler efficiency.

 

Shouldnt be a problem. Air flow wont change much at all, maybe if you put a really big intercooler on the car, there might be a 2 millisecond delay added into the turbo lag but its not gonna effect the way the car performs other than possibly bringing the charged air closer to ambient for longer periods of time.

The air flow passing the MAF and exiting through the lower charge pipe will pass the MAP sensors and the car will adjust fueling accordingly. This will not need a tune. i dont even think aftermarket charge piping will affect the way the car makes its adjustments since its MAP sensor controlled coupled with the MAF.

The only sensor that really messes with the fuel trimming and AFR is the MAF sensor at the intake.

 

Last car was an 04 sti. I agree the handling is quite good on this cobalt considering this kind of power being put through fwd. There is a significant difference though, but that's a bit apples to oranges and unfair to directly compare.

I will be getting another sti or similar later.

 

Fairly impressive; if it was just a failure due to vibration you would expect to have similar symptoms but see a crack; this looks like a straight up burst due to too much pressure for the material.

Were you on the car a lot before this happened (that would have significantly warmed up the plastic, reducing it's strength)?

 

45 minute commute from work it was an easy drive, I wasn't on it at all. Its one of the reasons I'm certain it was going to fail at some point, I'm glad it was near home.

 

Yeah, there's a little bit of price difference there, I'd say. Not really the same class of car. Personally, if I'm spending 35K on a car, I'm getting a German-make sedan.

 

What kinds of codes could you see from this? Besides the maf codes. I ask because i and many ithers have the trifecta Ecp which disables maf codes.. Could there be an under boost code from this (p0299)?

 

Yea, the main concern I would have worry is of **** getting sucked up.

The engine will set codes/go into limp mode as the MAP sensor & calculated airflow would be different enough to register an issue.

You would need the service manual to know what exactly the P-codes are. Well hopefully, sometimes the service manuals don't have as accurate descriptions as one would like. I work for a different OEM but there are times when I actually have to go to the OBD engineers to figure out what exactly is programmed.

If there is a fault that is described as a circuit issue there can be many reasons from my experience. You first would need to figure out what circuit the P-code was registered against. Many times there are p-codes for each wire and with the most basic sensors you usually will have 2 (power, output signal) or 3 wires (power, ground, output signal). The P-codes for power/ground usually are that there is a short somewhere and there is no continuity in the circuit. The P-codes for the output signals usually fall into signal outside of expected range, shorted to voltage, or shorted to ground. With more complicated devices the diagnostics get more complicated.

 

Sorry for the really late reply but I did not get that code even with basically no boost making it to the engine.

 

it is a fair statement. when I buy a car for 20+k I want somewhat decent quality, not plastic. I don't care if its made to handle stock conditions, which it really isn't cause lot of people blew there tanks due to cold weather and hitting a little bit of a bump. and some blew them on stock tune. also the charge pipe have been know to rip on the seem. im just tired of seeing plastic parts on engines. u wanna do that inside the car, fine, but don't put that bs on my engine. like on those vortec v8 engines. I was shocked when I saw the intake mani was plastic. what the hell man. u tighten one bolt a little to tight and there goes ur manifold.

 

And this is why I bought an upgraded intercooler yesterday.

 

I didnt read the whole thread, and this may be a bit off topic, but is it possible to just weld sheet metal end tanks on the stock unit? I was planning on doing that.