Ok. I've got a 2010 model. Yesterday, I removed the plastic cowl trim that covers the windshield wiper mechanism. I was just doing some cleaning of the drains under there and removing any stray leaves that had accumulated. Got a good handful of leaves out.

Now. I've read other posts regarding the butyl patch on the 06's. What shocks me is that on mine(and I'm sure other HHR's) that it's just 1 big open hole on the firewall. You can clearly see the cabin filter.
What the heck was GM thinking ? Why is it wide open where anything could fall in there ?
At the least, seems like there should be a fine mesh screen to cover that big hole and keep any debris out. I think I might just mount up my own screen now that I think about it.

Here's a few pics so you'll know what I'm ranting about.

 

The angles are so different I can't tell if they are in the same place.

 

I havent touched mine since I did the patch on my 06 but I think your hole is a bit different than mine..... XD As in mine is alot bigger. Like literally right under that patch is one giant hole whereas yours looks redesigned.

 

Yeah Don. The best I can tell is the old ones with the butyl patch had a full metal cowl under the plastic trim.
Take mine and based on your pic, this would have been where the butyl patch would be. Not sure why GM did away with extra metal area and didn't have a butyl cover or similar.

 

The hole you circled in #4 is the hole in the upper cowl to which the cowl patch is applied, note were the cabin air filter is and the way the metal is shaped to keep water away like a damn . My 2007 has this same as your 2010, no leaks , but if enough water got past the black plastic cowl cover, it could cause problems.
Anybody have pictures of their 2006 under the butyl patch?



This kinda shows the hole goes much farther to the base of the windshield!

 

That shows the corner of the inlet for the fresh air. Looks to be the same as mine as far as the inlet that has the cabin filter.

 

Yes, and that patch is folded down to funnel water directly into the cabin air filter, into the HVAC blower and the passenger side footwell.


Here we see the metal is beaded along the same line where the 06 has the opening

 

Looks like metal has been added here.

 

Yes, carrying water out over the cabin air filter.

 

A little update.
You know I couldn't just leave it alone. That big open "leaf/debris catching "hole just wasn't going to work for me. Not worried about water getting in there, just all the other things that could.

So, today I took off the cowl cover again and put a piece of plastic mesh screen over the hole. It's just taped down with added attachment from those plastic lock tabs around the hole. Cut a small slit in the screen at the tab locations.
It doesn't have to look pretty since you can't see it.

Anyway. I feel better now that I know the hole is covered somewhat.