Since September of 2018, when I'd start the car with the HVAC system on, it would stink really bad for about a minute and then sort of go away. When I'd use the remote start and stand near the car, I'd smell a very bad smell coming from it that was detectable several feet away. Wasn't sure what was going on with it until recently I pulled t he heat shield off the exhaust manifold and found that all too famous crack between cylinders 2 and 3. I was certain I had checked it before but I found that it was cracked underneath as well so it's possible it started there and spread over time since we had some cold weather this winter and with the hot and cold cycles, it probably kept getting worse and worse.

The garage quoted me about $350-$400 to fix. I ended up replacing it myself for about $100. It's not the worst thing in the world to do but can be difficult due to frozen nuts and bolts. If need be, spray some penetrating fluid on them and let them sit a while and maybe spray them again for good measures. Just don't get overzealous when trying to remove any nuts or bolts as you'll be in for a lot of hurt if they snap. You can use a Dorman manifold and it works okay but I'd suggest getting genuine GM gaskets instead of using the ones in the kit, the ones in the kit don't seem to seal very well and can still cause leaks and loud engine noises.

It's pretty upsetting that GM can crank out trash parts like this and then not even try to own up to their mistakes and at least help the customer. Parts fail, I get it, but exhaust manifolds shouldn't crack. When you have consistent cracks in the same place on the same types of Ecotec engines, you know that it's not what the customer is doing, it's your own shortcuts that got them to that point in the first place. Shame on GM, seriously. It was to the point I didn't even like my Malibu anymore and was thinking of trading it in until I finally found the problem and corrected it.

The symptoms of a cracked manifold on all vehicles using the Ecotech 2.4l is an intolerable exhaust smell when you first start the car with either the heat or AC on. The exhaust manifold is directly behind the firewall, which sucks right into the cabin, and the smell is horrible. What concerns me most is, once the car is warm or in motion, the smell almost vanishes or isn't nearly as bad.

This gives a false sense that it's not a serious problem. I'm not certain what long term (or immediate) impacts breathing exhaust are, but it can't be good. I drove this car on a 15 hour trip a few months ago. While I couldn't smell exhaust while driving, it was almost certainly there. I read this is a fairly common problem with the Ecotech 2.4l, although this website doesn't have a ton of reports.

It amazes me GM can put out such a low quality manifold. This is cast iron, it shouldn't crack so easily. The replacement part itself isn't all that expensive, I found the entire kit including the manifold gaskets, and bolts for around $70.00. However, it's not all that easy to get the old one out and new one in. Luckily for me, the crack did not go all the way around, and as a temporary fix (until I decide to tackle this and replace it) I used JB Weld Extreme High temp to fill the crack. It works for now, but I imagine the crack will continue to spread over time.